Spiral of death:
There is currently no stall prevention logic, and the result is for some unknown reason a steep (70 deg +) spiral dive with ailerons hard over. The Gemini V-2 reached 31 meters per second airspeed from a height of 123 meters, and pullout was at 12 meters height agl.
Barely above the treetops
It's very important to come up with a valid figure for FBWA minimum airspeed to enter into the PIXHAWK 's parameters. Simply stalling the aircraft in manual mode and recording that as a value for minimum airspeed is not good enough to allow stall prevention to work properly, and may result in the PIXHAWK thinking that a stall has occurred even if the wing has not lost lift. The key thing to look for is the separation of the desired pitch input from the actual pitch moment in the pixhawks data logs after performing a stall in flight using manual mode. Seeing where this separation starts, and then using the airspeed at which it occurred, or preferably a slightly higher one will produce a more accurate figure to enter as a minimum airspeed for PIXHAWK, because it's all about keeping the autopilot from detecting a stall, as this can happen at a slightly higher airspeed at which the wing actually loses lift.
Airspeed sensor calibration:
The airspeed sensor calibration is very critical to the safe operation of the aircraft using PIXHAWK.
This is best done in light wind conditions, as it will require flying in circles, and if too much time is spent flying in one direction (into the wind) during each calibration period, an accurate result will not be obtained. It's also a good idea to fly the aircraft at 2 different airspeeds (at least) during the test, say at a loiter speed for 3-5 minutes, then at cruise speed, to give the calibration a wider spectrum of figures to process, and in theory, a more accurate result.
Note that it is also crucial that the tubes connecting the sensor to the pitot port hold air pressure, for an accurate and consistent reading.
There is a unique characteristic of the sensor itself, that should be taken into account regardless of the mounting location of the sensor itself, that being the sensitivity of the digital chipset on the sensor to light. This is essential if the sensor is to be mounted externally, or even internally if there is any chance that light could enter the compartment where the sensor is to be mounted. Even reflections from the landing gear strut below entering though a small slit in the nose fairing for instance, could disrupt the sensor calibration momentarily, enough to cause a malfunction in flight, resulting in a crash. Mounting the sensor inside a transparent fuselage, such as in a EPO or EPP foam airframe is not enough to prevent the problem from occurring, and additional measures should be taken to ensure no light reaches the sensor chipset.
In our testing, a 6 meter per second difference was measured when a member of the flight crew walked past the aircraft while on the ground, and the shadow of his leg passed over the externally mounted sensor. A black piece of heat shrink over the entire sensor solved the problem, enabling us to finally calibrate the sensor successfully. We were fooled the day before when we did the calibration flight at dusk, just after the sun had dropped below the horizon, then tested it that night in the dimly lit hangar, by blowing air past the aircraft using the propeller from another model. It appeared to work fine, but the next day in direct sunlight, it was clear that something was gravely wrong with the calibration. That is when we noticed that the reading jumped dramatically when in a shadow. In retrospect, it was a good thing that we mounted our airspeed sensor externally, as we learned of this issue, and it could no longer lurk, waiting for just the wrong circumstance ( a momentary reflection) to destroy our test aircraft.
It's desirable that cruise speed be set at least 3 meters per second faster than the minimum speed, otherwise banking will be restricted during cruise to as little as 25 degrees by the stall prevention system.
We prefer to set the maximum airspeed just slightly above the cruise speed, as it does no good to have the aircraft going faster in a descent, just bleeding off kinetic energy, and reducing flight time/distance.
If flying in windy conditions, a slightly higher cruise speed is desirable. If flying in calm conditions, an airspeed just a few kilometers an hour faster than the best loiter airspeed is desirable.
CG and how changing it affects the autopilot:
It's important to be mindful of the CG of the aircraft, although not really more critical to the autopilot operation than in manual flight mode, it will have an effect on flight dynamics (the way the aircraft responds to the flight controls)
Most conventional aircraft will have a range of acceptable locations for the CG and the aircraft will have different characteristics when flown with different CG locations. For instance, at a forward CG location, most aircraft will be more stable in pitch, yaw, and also be more spirally stable. The stall usually happens at a higher airspeed in level flight, and will be harder to stall in the first place. It may also be a more abrupt stall, depending on airfoil selection and Reynolds numbers.
An aft, or rear CG will usually stall at a slightly lower airspeed in fwd flight, but also have a more gentle, gradual stall characteristic, in the case of the Gemini v-2.
Another advantage of a more aft CG is that the aircraft will be more efficient in flight, especially at lower airspeeds and higher angles of attack. This is true because the down-force needed for the aircraft to maintain pitch trim is less with an aft CG, and depending on the angle of attack (high angle of attack at very low airspeed),the horizontal stabilizer and elevator can actually produce some lift, affecting the overall lift to drag ratio in a positive way. At higher airspeeds and lower angles of attack, this will be less true, as the coefficient of lift required to maintain level flight is less, compared to the airfoil's potential lift. In this higher speed cruise condition, a small change in the lift to drag ratio will have less effect on the total aircraft performance.
In short, it is recommended to find the CG that you are most comfortable with in manual flight first, and then mark a precise location to use for all auto tune and autopilot controlled modes, including fly-by-wire, and stall testing in preparation for setting the minimum airspeed. It's also desirable to have the aircraft flying at the maximum weight desired when doing all of the testing. It's okay to remove weight after testing, but risky to add weight afterwards. The effect of Variable drag devices such as air brakes, retractable landing gear or retractable external payloads/sensors should be of little consequence to the minimum airspeed values, but should be taken into consideration when setting the maximum airspeed value, or descent angle with power off. It's better to have the aircraft in the clean configuration to collect data for max descent angle and max airspeed, and be sure that the values selected allow for a sustained descent, not just a brief descent for a few seconds. This will be even more important when flying auto missions using the terrain following feature of PIXHAWK, or similar autopilots, as the descent path is not directly setup by the person planning the mission, but also depends on the autopilot 's decision to descend in order to follow drops in terrain.
A similar warning is in order for the full power climb. Giving the PIXHAWK authority to use 100 percent throttle is fine as long as the power system can handle it for extended periods of time. Keep in mind wiring, arming switches, current sensors, and battery discharge rates/ cooling when setting up the power system. Each component should be slightly larger than it has to be in order to survive continuous operation at maximum power settings.
Most aircraft will high aspect ratio wings, such as Gemini V-2 will need considerable rudder mixing(aileron as master and rudder as slave). This is due to the "adverse yaw " effect that the ailerons have when actuated.
One aileron will go down into highly pressurized air and the other will go up into less pressurized air. The aileron going down will generate more drag, and the one going up less drag. The effect on the aircraft will be that when aileron is applied, say to the right, the offset drag will tend to yaw the aircraft in the opposite direction. The proper way to tune the rudder mixing is to fly the aircraft in manual mode with the mix set at your best guess as to the correct amount, and while flying toward the pilot/observer, rapidly bank the aircraft left, then right, using the ailerons. It's best to do it at full stick deflection, but do whatever seems safe. Observe the yaw movement, and adjust the rudder mixing appropriately. Alternately, and perhaps more precisely, an on board camera can be played back after the flight, and the yaw movement can be seen easily from the footage. Do not make adjustments based on one movement, but if it shows consistent movement in the same direction as the roll input, then reduce the amount of rudder mixing. If the plane's nose consistently yaws in the opposite direction from the roll, then increase the rudder mixing. For Gemini V-2, it's best to start with roughly 85% mix, in the same direction, then adjust from there.
The percentage figure that you end up with can then be entered into the PIXHAWK 's rudder mixing parameter, but then an important step must be taken, to disable the control system mix when in fly-by-wire a mode, and all other modes. Failure to disable mixing of the rudder in the control system, when in any mode but manual, will result in a rudder hard over condition in fly- by Wire mode, during normal turns. The rudder will overpower the ailerons to some extent, resulting in a bank angle exceeding the limits set for max bank angle in PIXHAWK. Another problem with this condition is that the aircraft will effectively have its controls crossed, with the rudder trying to turn into the turn, and the ailerons trying to turn the plane the other way. The resulting drag penalty is severe, and other aerodynamic phenomenon related to effective airfoil shape and effective platform of the wing will also have a bad effect on the aircraft. The loss of proper control and waste of kinetic energy during the turn will most likely result in a stall which the stall prevention logic in PIXHAWK is unable to prevent. This condition can be predetermined on the ground before flight to ensure proper control system setup by putting the aircraft in fly by wire mode, then tilting the aircraft past it's max bank angle, with roll (aileron) applied in the same direction as the tilt. The rudder should reverse direction in the same direction as the ailerons after banking the airplane manually past it's maxbank angle set in PIXHAWK. If the rudder stays hard over in the same direction as the turn, the aircraft should not be flown until the control system is properly setup.
download mission planner and drivers from ardupilot dot org
flash firmware to pixhawk with USB cable
open mission planner, go to config/tuning, go down to layout, select advanced, and then parameters can be loaded.
load param. file for airframe
First, perform any physical mods to taranis before configuring.
next, flash newest firmware to Taranis.
load Bin. file to taranis by extracting micro SD card, inserting in micro SD adaptor in usb port on computer, go to model file, trash current file, then load correct (NEW) model file.
eject from computer,
Re-insert in Taranis.
Turn on Taranis
go to model program, select an empty slot, such as slot 2, then press and hold enter. Go down to “select model” option.
hit enter to load model .
“Tesla” battery for Taranis:
2-2-2 (2 in parallel and 3 sets of 2 in series, for a total of 6 cells)configuration. 11.1v nominal 12.6 fully charged. 7.5 lower discharge limit max
case dimensions in 3mm pvc foam board (see our original “Tesla" style battery build for the plane for reference on general battery build principles, including charging port, (XT-60) and balance port (XH style):
base 108 x 30 mm
sides: 72 x 108mm
Top: 25 x 108mm
Ends: 25 x 48mm
change settings of Taranis to :
voltage range of meter: 12.7v to 7.5v
alarm voltage 9.6-10v recommended (use your own discretion, but remember that you want plenty of warning for possible TX battery failure to give time to bring the model back safely).
Download immersionrc tools from immersionrc.com
download drivers if necessary
connect TX and RX separately, in immersionrctools, and read settings to check.
Flash with latest firmware, configure for S-bus (receiver only)
set frequency range (same for both RX and TX)
plug-in TX EZUHF module to taranis
switch EZUHF module to low power
hold the failsafe/bind button while turning on.
as soon as periodic beeping starts, let go of the button.
The EZUHF TX module is now in bind mode.
use the bind feature of the ImmersionRCtools program with the receiver plugged in, to bind the
receiver to the transmitter.
Alternately, apply power to the receiver, and within 10 seconds, hold down the bind button on the receiver, between the two boards.
The LED not he receiver should (after less than 1 second) extinguish, and shortly thereafter, flash 3 times, indicating bind success.
If it flashes 6, or 10 times, binding was unsuccessful, and must be re-attempted.
power off the TX and RX module, and then power on again, to exit binding mode, and to make sure that binding is successful. there should be a heartbeat visible on the receiver LED, when packets are being received. turn off the transmitter, while leaving the receiver powered on, and then you should see the LED status change (heartbeat fade) within 1 second or so, indicating that link with the TX is lost.
We suggest not using the antenna that comes with the EZUHF JR TX, but instead suggest substituting it with the Diamond SRH771.
Install equipment in aircraft
ail1 - ailerons with Y harness
ele2 - elevator servo
thr3- ESC’s with Y harness
rud4 - rudder servo
RC-5 nose wheel servo
SIK radio - telem port 2
OSD radio -telem port 1
buzzer - buzzer port
gps - gps port
remote compass integrated into GPS receiver antenna- I2C port
arming switch- switch
I2C- I2C expander port (backbone serial port)
USB to remote USB
Remote LED to I2C port
Atto 180 amp module with 10 amp castle BEC set to 5v - power port of Pixhawk
RC-8 servo plug - zeener diode 5.6v plug with 10v 1000uf electrolytic capacitor
( cap white band to negative ground / zeener diode in parallel with white (or silver) band on the positive side) power is fed with two silicone diodes (or alternately, a re-purposed rectifier diode assembly, wired differently, and with a smaller, lighter heat-sink), and powered from 2 separate BEC's (20 amp castle creations set to 5.5v each) from the main flight battery, via a connector closer to the battery than the main power plug, or current sensor, so that if the current sensor melts, the pixhawk will still have power. The zeener diode and capacitor should have oversize wiring and be relatively close to the servo rail.
Plug in USB modem into windows PC and drivers should install automatically. If not, prompt windows to diagnose, and fix problem, and it should install the drivers then.
plane modem should be plugged into telem 2 port on pixhawk
select com port 6 (silicone labs CP210X USB to UART and baud rate 57600.
SIK radios should now be able to link wirelessly with Mavlink (Micro Air Vehicle Link)
by using the connect button on mission planner when plane is powered up.
mandatory hardware, and go through steps, using a level, etc. hold plane as still as possible.
check HUD for valid and accurate readings in all attitudes after completion. set level position.
Compass calibration process:
Use an open area with at least 10 feet separating the pixhwak from any metal objects, or concrete, which may contain metal, etc.
remove belt buckles, and keys, etc.
with computer connected via mavlink, go to config menu
select mandatory hardware and select compass calibration
select live calibration.
wait for good GPS fix, (solid green light for more than 1 minute before starting calibration)
start, and immediately uncheck the “auto accept” box in the menu.
hold plane and rotate at least 2 full turns with the plane in the following orientations:
1 right side up
2 upside down
3 on the plane’s right side
4 on the plane’s left side
5with the plane pointed straight up
6 with the plane pointed straight down
now move randomly, in all positions possible in between, until 1500 samples are collected.
check the auto-accept box, and continue to move the plane randomly, getting as many data points as possible to make as complete a sphere as possible, and while hitting all of the white dots if possible, until auto accept stops the process.
accept the offsets, and they will be stored in the pixhawk’s memory.
decide whether to use both compass readings, or only the external. i’m guessing both?
under config menu in mission planner, go to mandatory hardware, and click radio calibration.
follow prompts to calibrate. move sticks quickly, and fully to each corner, and each switch, regardless of whether it is used, just in case.
Before first flight checklist:
Manual mode: test and measure control surface throws, and responses to all controls.
FBWA mode: Test control responses, and Auto level/ damping responses.
Perform spectrum analysis with immersionrctools. Noise floor should be BELOW -70db. (preferably below -90)
Real world range checks at low and high power mode on EZUHF.(high power should go slightly further - at least 10% further - than low power).
Check failsafe response of autopilot. When radio is shut off, autopilot should enter auto mode, and if no mission is set, should circle for some seconds, (10-20) then RTL.
If a waypoint /waypoints are set, it should continue the auto-mission.
Check CG, and right/left balance of airframe, making sure it is exact.
Turn on everything, and perform a full ground test of all equipment.
fully charge batteries:
1 flight battery
2 TX Taranis battery
3 Laptop battery
any other batteries in cameras, etc, that are to be used
clean memory cards on all cameras, and other devises, such as DVR’s.
Fly plane in manual mode. attempt to perform stall power off, etc.
Briefly (at least 1 minute) fly the airplane in a figure 8 using FBWA mode.
Perform airspeed calibration/verification.
Second flight: Use Auto-tune for pitch and roll, 100 cycles each (or verification of these from the flight data logs after performing the maneuvers in FBWA mode)
Third Flight: Test FBWA mode extensively- Sustained over bank / powered off stall / full climb under power with stick all the way back.
Fourth Flight: Test Auto on small (within visual line of sight) waypoint route in Auto mode.
Test Auto on large and more complex waypoint route.
Info for minimosd:
That page should link to the tool and
Should have a list of firmwares.
To interface with the MinimOSD, you will need a FTDI basic breakout board, available on Ebay or at your electronics store (perhaps). These are commonly used to interface with Arduino boards.
There are two ends of the board, the digital end plugs into the Pixhawk, with the 6 pin connector, and the Analog video end of the board, which controls what you see on the screen.
you will need to have both ends powered up in order to complete the configuration of the board, for your use. Some boards have a bridge, that powers the analog end from the digital end. and there are two identical red led’s on each end of the board, to let you know when each side is powered individually.
The digital end will be powered by the Computer (PC) through the USB cable connected to the FTDI board, connected to the MinimOSD.
The Analog end will need powered too, by 12v, so the easiest solution for us FPV’ers is to use a 3S lipo to power it, and an XT-60 to servo adaptor with no need for the signal wire, or the signal wire removed.
be careful with this, and observe polarity,(marked on board), as it is possible to get the polarity wrong, and fry the analog side of the board. It happens very quickly, or so i’m told.
The board may get slightly warm when powered by the 12v, but should not get hot.
So, with the Analog side powered up, plug in the FTDI adaptor, observing pinouts and matching them, with the exception that the RX and TX will be reversed. (This is because the FTDI board is giving data, and the MinimOSD is receiving it).
now plug in the FTDI end of the USB cable, and then plug in the USB cable into the computer last.
This sequence is important to prevent static damage to the board, in high static environments.
There should be a message on the PC saying “Installing device driver software”
after a minute or two, you should get a new message on the lower right hand corner of the screen, saying “ device driver installed successfully”.
Now you need to go here,
and download the CT tool for MinimOSD.
It comes in a ZIP format, and is automatically put into your downloads folder. You can find it by going to the windows icon, typing in downloads in the search, hit enter, and then click on the downloads folder. you may recognize it fly the name, but you can also look for today’s date to find it.
Now, you can extract it to your desktop, by right clicking on it, and selecting “extract to this location”
select desktop. The config tool folder should now appear somewhere on your desktop.
It should be called something like CT tool for MinimOSD. inside it is an .exe file called OSD_Config
It should have a graphic symbol associated with it, using an OSD symbol.
double clicking on this will open the tool.
First select com port 5, so that it can talk with the FTDI board, that is connected to the MinimOSD, or whatever com port is related to the FTDI/ USB cable.
Go to video mode, select NTSC or PAL, depending on your video system. In my case, it was NTSC, as i’m in North America.
before going to the next tab, go to the bottom right hand corner of the window, and click “
Save current tab to”. You should get a confirmation that settings have been saved.
Next, select the tab, Panel.
Warnings panel 1,
OSD toggle disabled
No rotational switching (uncheck box)
Stall speed about 45kph
overspeed about70 kph (or whatever settings you are using on the Pixhawk config for min airspeed, and max airspeed)
I like med-high brightness (your preference)
min battery voltage 9.6
batt warn 10%
click on save settings, and you should get a confirmation,and a tone from the computer/flash from the MinimOSD board.
click on panel 1, which will be the only active panel, unless you opted for OSD toggle function.
Select any of the functions you will want on your Screen during flight.
(tip: if you cannot find one of the functions, or uncheck it’s box, and you do not see a change, it is probably being covered by one of the other functions. Your can also use the mouse, to drag the figures on the screen to a different location. Arrange them as you like.)
GPS Coord (incase your model ever goes missing, you can look at the last known GPS lat/lon, and start your ground search using a handheld GPS at this location.)
Heading Rose (this is probably antiquated, but i like it.)
Home altitude (this is set when you arm/first get GPS lock)
Horizon (artificial horizon is great for flying in IFR conditions, if you ever go cloud surfing and get lost in a cloud, it could become a very important safety feature)
Pitch (this is pretty optional, but helpful when you are turing an autopilot, and want to see if the bank angle is being properly limited by the max roll angle parameter)
Roll (same goes for this as pitch)
Throttle (this shows throttle position in percent on the screen)
Trip distance (not really necessary, but an interesting fact, and maybe helpful when adjusting the flight plans for auto missions)
Velocity (this is the GPS based Speed/ Ground speed)
Vertical Speed (in meters per second)
Visible Sats (helpful in determining whether to arm, or fly)
Warnings (This displays Flight control warnings on screen, for FPV flying, or it can help you know when the autopilot is exceeding one of it’s parameters momentarily. This may help you to make the config settings or flight plan more efficient, as if min airspeed or max airspeed is being approached, or exceeded, the plane is not flying in it’s ideal flight envelope.)
Before moving on, now click the “Save current tab to” button on the bottom right hand corner of the window. You should get a confirmation that settings have been saved.
With CT tool for MinimOSD still open, click on options tab, Update Charset, (this will determine what characters are used such as language, etc.)
click on update Charset. You can then search for the Charset. To find it, look on the desktop,and find the CT Tool for minimOSd folder, and look for the folder marked minimOSD2.3.20 mcm. file, or newer version, that you have downloaded, as part of the package.
highlight it, and click open.
You should get to watch the progress bar in green on the bottom advance, indicating that The Charset is being loaded, and get a confirmation.
Next is to upload the firmware to the MinimOSD board. Go to options tab again, and select upload firmware. select the firmware you downloaded. It may be in the "CT Tool for MinimOSD” folder, or if downloaded individually, it may be in the downloads folder, or on the desktop. It’s a Hex. file.
highlight it in the window, and click open. you should get to watch the progress bar advance, and get a confirmation that the firmware upload is complete.
You can now close the CT Tool for MinimOSD, unplug the USB cable from the computer, and then subsequently from the FTDI adaptor. Unplug the FTDI Adaptor from the MinimOSD board, and finally, unplug the custom XT-60 to servo + - lead from the board, de-powering the analog side of the board. again, check the temperature of the board, it should be warm, but not hot. This is similar to the temp that it will be running when on board the aircraft, so consider this when planning for cooling of the board with the airflow over it when in flight. (it may or may not need any cooling).
To Purchase Future Star plans,
Just click here:
Future Star - Additional info
probably more than you ever wanted to know....
The Most Interesting Park flyer in the World...
The Very First Prototype Flying:
Air Launching Future Star:
When it came time to air launch, we were a bit nervous. However, we had nothing to worry about, as when Future Star released from the V-2 mother ship, there was hardly a twitch. We experienced very clean releases every time, and this phase of flight was never a problem! The 45 deg. angle of Future Star's main Stabilizers insures a smooth separation from Gemini V-2, or other mother ship with a square fuselage.
Landing in Captive Carry mode:
As there is still plenty of ground clearance beneath Future Star's wheels, landing Gemini V-2 with the Future Star still attached, was not a problem at all. The Future Star tail fairing is raked up, on the bottom, to provide extra clearance upon rotation for takeoff, and flare for landing. In case a hard landing were to be experienced, the first thing to touch would be Future Star's main wheels. This would help cushion, and even straighten the ground trajectory.
Firing the Rocket Motor in Flight:
The rocket motor can be fired in flight at a surprisingly low altitude. However, we recommend at least 100ft the first time, to avoid any unintentional consequences. With an experimental aircraft, especially one with a rocket strapped to it, failure is ALWAYS one of the possible outcomes. We have strived to create a redundant, stable, platform for rocket plane experimentation, and the rocket motors themselves from Estes, have been very reliable. However, it must be kept in mind that a rocket motor is inherently dangerous, and is essentially a controlled explosion, so take the proper precautions. The rocket motor can be fired in level flight, vertical flight, or at any angle in between. When fired in a near-vertical orientation, it may not be necessary to reduce power to the electrical motors, although there is a significant boost to the thrust. The rocket motor makes enough thrust by itself to propel the craft straight up, and so do the motors. The center of gravity will change slightly when the rocket motor is ejected, so set the balance without it installed.
Alternate power setups:
Future Star will fly acceptably with smaller motors, such as the "blue wonder" type. Unlimited vertical performance will not be possible with such motors, however, a lot can still be done with them. Most of our flight testing for prototype aircraft was done with these type of motors.
Evolution of the concept:
The original concept was to fit underneath any airplane with tricycle gear, and for the front, and rear wing to be the same. The fuselage was also to be square. We went through the process of building and testing 3 separate, and different "Future Star" concept aircraft before the final version. The first 2 had very poor performance.
The breakthrough came when examining the fuselage cross section, and drag profile. We had the idea to make the fuselage angular, to reduce drag. We knew we would have to re-configure the aircraft. However, a drastic change was necessary. It turned out that the angular fuselage provided just the right possibility for location of the main stabilizers, in just the right place to support the motors. It's important that the propellors clear the rocket plume, or else they would be burned, and out of balance when they were needed most. We would have to use 2 different wings, but we saw a way to make one of them very simple. For that 3rd version, we also did a drag benefit study on the tail fairing, realizing that tapering it to a point was not very beneficial, and added crucial weight aft. A better solution was to shorten the fairing. A reduction of just over half of the fuselage cross-section was enough to reduce roughly the same amount of drag as the previous fairing. This also allowed the fuselage to be shorter, and the aircraft to be lighter overall. The only problem left was one of balance.
The aircraft still needed too much nose weight to balance. A re-designed nose allowed the battery to be shifted forward, and changing the sweep of the forward wing made the final difference to the location of the center of gravity relative to the center of aerodynamic pressure of the fuselage.
It's important to mention that all of the prototypes flew decently, even though some experts said that they would not be able to do anything but fall, or that they would not be controllable.
More about the Captive Carry Configuration, and Mods to Gemini V-2 for Air Launching of Future Star:
I'm often asked what control system I use for Gemini V-2, how to set it up for long range, and how to setup the head tracker, so here is some info on that , that may help you:
Immersionrc EZUHF TX and 8 ch diversity RX
Following is a video that was made to address the firmware update, binding and configuration of the EZUHF gear:
Laser Cut Kits Available!
Contact Wayne (Flying Squirrel Models):
More info about our "Tesla" style Battery:
Original Concept Sketch:
Some pictures of the mods to Gemini V-2 in order to carry Future Star:
How strong is the airframe of the V-2? well, in this video, the autopilot causes the aircraft to dive steeply and reach an incredible speed for which it was not designed, requiring manual intervention, and a sharp pullout, with over 3 G's of positive load on the high aspect ratio wing. The gimbal captures the whole thing, and inspection of the airframe revealed no flaws. We were able to locate the faulty autopilot setting (user error) and continue flying the airframe with no repairs necessary to the airframe. you can read about the autopilot settings above that caused the incident, so that it does not happen to you!
Angular Fuselage concept sketch:
A warning about E-flite 80 amp pro ESC's:
switching to Castle Creations "Talon 90" ESC's solved this problem, and we have since put many flight hours on this airframe with no further problems. The cause was due to ripple current, and the poor quality of the capacitors installed on the E-Flite ESC's. The startup is also rough sometimes, probably due to poorly written firmware loaded onto the ESC's. at any rate, we recommend avoiding them altogether.
People often ask me about propellor efficiency. For our model planes, and UAV's, it mostly depends on one thing, the propellor. it's important that the propellor be an efficient one for the type of use. In the cased of electric powered fixed wing aircraft, i have found no better than the APC thin electric series props. the only questions then is what diameter, and pitch. the diameter is the determining factor in the loading of the motor, but in general as large as is practical is best, as long as the motor can spin it at full rpm without overheating. The motor manufacturer's recommended prop is likely to overheat it, and it's important to look at the watt rating of the motor, as this takes into account the voltage, and also the amperage involved. You can think of the motor as the last point where the heat in the wiring, and power system builds up, so the total watts is very important there.
The wiring is a different story, as the amperage is the only factor in sizing of the wiring, and other inline components such as ESC's, connectors, and current sensors. so it is good to leave some margin , and use a slightly smaller diameter prop than the maximum recommended for the motor for hobby use. Next is the pitch of the prop, and for efficiency, i have found that a ratio of about 1 / 1.7 of pitch to diameter is close to ideal for long duration flights. It also gives room to increase throttle at higher altitudes, where higher airspeeds are needed to generate the same lift, even though indicated airspeed may be the same. So, if you have a 17 inch prop, about 10 inches of pitch would be nearly ideal.
The Final Version of Future Star:
This V- shaped chock keeps Future Star aligned with Gemini V-2 during "Captive Carry".
Dual Servos / Split Control Surfaces Mod
This mod increases the chance that you will be able to land safely, in the unlikely event of a servo failure. This mod is something to consider for high value sensor payloads, or if you plan on putting a lot of flight time on your airframe. In this case, all 4 servos for rudderX2 and elevatorX2 were housed in the vertical stabilizer.
2nd Prototype was more Robust.
It Suffered from Poor Performance:
A few notes on installing PIXHAWK
autopilot in the Gemini V-2 airframe:
Can be flown With our Without Gemini V-2!
Some notes on our “Tesla” style battery:
Do not operate, or charge the battery at very low or high temperatures. Room temperature is best. It is ok, maybe even good, to store the battery at relatively low temperatures, but never below freezing. Do not leave the battery in a hot car, or other hot environment. Nothing really bad should happen, but exposure to 100deg. + f. temperatures will damage the battery slightly over time. This is true of almost all lithium cells, including lipos.
Make sure you use a balancing charger. Some chargers top out at a certain capacity, and some stop charging after a specific time period. For this reason, due to the very a large capacity of the battery, it may be necessary to reset the charger more than once during the charge cycle, due to these common limitations of the software used in some chargers.
It is best to charge the battery just before using. Avoid leaving it fully charged for long periods of time. Several hrs is fine, and a few days won’t hurt, but if you plan on using the battery in more than a few days, it is best to use the storage mode of your charger. Storage voltages vary, but it’s not critical. Any lipo storage voltage for 3s should work just fine. It is possible to store the battery for a very long time using this method.
The battery cells ship at 3.62v per cell, so that is a good baseline, if your charger requires you to enter a voltage.
You do not need a special charger. A standard, hobby grade smart charger for lipos is fine. The lipo mode setting and voltage is perfect for this battery type. For maximum battery life cycles, do not exceed 4.2v per cell, and do not discharge the battery to below 3v per cell. 3.3v maximum discharge per cell should get you hundreds of useful cycles.
The cell manufacturer states that the cells can even be discharged to 2.5v per cell, but we do not recommend it. They admit that if this is done, the cycle life does drop significantly. In theory, if you treat the battery nice, and keep it within slightly tighter parameters, you could get thousands of useful cycles!
You can refer to our torture test below, represented in the first graph, to get an idea of how the battery holds up to higher discharge rates. We have tested it in-flight by discharging at 30 amps at nominal voltage for almost the entire discharge cycle, and found no problem with overheating. In fact, the battery was cold. This test took 1 hr 20 minutes for discharge. It is possible to discharge at much higher rates continuously. As is true with any lithium battery, the higher the discharge rate, the less capacity is able to be delivered. So keep in mind that the effective energy density of the battery is less at higher discharge rates. If you plan on loitering for as long as possible in flight, it is best to avoid steep, prolonged climbs, and high rates of discharge during the same flight. Flying at a low airspeed is the best way to achieve this. Gemini V-2 loves to fly at about 144 watts discharge at about 42km per hr in loiter mode. This produces flight times of up to 4+ hrs.
The payload capacity is also increased by using our Tesla style battery. The new battery is almost 2 lbs lighter than the lipos that we were previously using, and also has significantly more capacity. This represents a large gain in overall performance.
A situation where it is best to go back to lipos, and avoid use of the “Tesla” style battery, is when you wish to carry almost all of the aircraft’s available weight capacity in payload, and therefore wish to use a very small capacity battery. For reasons of discharge rate limitations, We do not make a smaller version of the battery, using NCR18650B cells, For this circumstance, it is actually better to use NCR18650GA cells, or lipos. Just be sure that the lipo you use for that purpose has a relatively high C rating. Many manufacturers lie about the C rating, and many times it is only half of what is claimed.
The battery can be discharged at up to 2C for burst, but we don’t recommend that. It is not possible, with Gemini's power setup, to discharge at a c rating of 1 or more. The power system does not pull that many amps. Use of full throttle should discharge the battery at slightly less than 1C, which is well within the limitations of the cells.
Make sure your Aircraft has good ventilation to the battery compartment of fresh air from outside the aircraft, and also make sure to allow the air some place to exit out of the back of the craft. This will help cooling in most climates, and ensure that the battery performs well in flight.
We sincerely hope that your use of this battery opens new horizons for you, in terms of flight time, range, and payload capabilities. Make sure to fly safe, and follow good practices when using, or charging any lithium battery!
Here at Bearospace Industries, we think this cell technology will someday dominate the hobby market, as well as most forms of transport.
More info specifically about the Laser Cut Kits for Gemini V-2:
Laser Cut Kits Available!
Contact Wayne (Flying Squirrel Models):
Plans Printing For all PDF plans- Boats, Aircraft, and Spacecraft:
When getting the plans printed from the supplied PDF files, It's important to understand that the PDF document has a built-in scaling system. a part described on a PDF has an inherent size, in 2 dimensions, and if the printer is accurately reproducing the file onto paper, there should in theory, be no issue with the scale of the print. However, due to (mostly operator) errors made when setting up the printer, people often experience trouble getting the size of the prints they ordered to come out correctly, to match the intended size of the aircraft, and to match the specified materials.
In these cases, the operator of the printer must be informed of the desire of their client to NOT have the scale of the PDF document altered during printer setup. During setup of printing of most documents, in day-to-day life, it's convenient to alter the size of the document to fit the paper intended, and the re-sizing, when necessary of the finished product has little consequence to the client. So, most print shop employees usually ask what size of paper that you would like the document printed on, and then alter the scale, and proportions to fit. If you are asked, simply respond to that with "I don't know what size of paper It will fit on, but please do not change the scale, or proportions. Use whatever proper size necessary to achieve it."
You may explain that the Pdf is already scaled. If they disagree, It may be better to find another print shop, or ask for a manager, or technician from the company to have a look at the matter. Many new employees are unaware of the scale of Pdf documents, and do not understand.
We hope this clears up some confusion, and gives you a strategy to get acceptable results from your local print shop.
Keep in mid that If a printer feed is not calibrated properly, you may not get a good result, and most results are not perfect, but if they are close, and relatively consistent, it should work. It's always best to use the best quality "professionally maintained" printer at a good print shop, than to go to a cheaper print shop with questionable machines.
Finally an prototype with outstanding performance!
Tried it first without the winglets...
More about the 4+ hour endurance flight using the "Tesla" style battery:
The flight was made in overcast, cloudy conditions, at low altitude. It was a windy day with turbulent air conditions, relatively cold temperature, and no significant thermal activity.
The aircraft was configured with FPV equipment only, and no payload was carried. Tricycle landing gear was used, and the wheels were swapped for slightly smaller foam wheels. No other modifications were made to the aircraft, and no special effort was made during the build to make the airframe lighter than normal. The flight was made manually, and the elevator was not touched through the entire flight, except for takeoff and landing. The only corrections that were made were for trajectory. We forgot to set the home position before takeoff, so we were without the usual GPS data for the flight. Aircraft Weight for the endurance flight was 7.855kg, or 17.325 lbs. Telemetry data for time recording was slightly off by several minutes, however we used two cellphone clocks, and a digital watch to record the total flight time. Total time in the air was 4 hrs, and 2 minutes. The full video of the boring flight can be found on our "bearospaceinsider" channel on youtube.
4+ Hr Flight Time!
Battery Log over 4 hrs/ (Data from ACTUAL Endurance flight Using Gemini V-2 airframe):
Battery "Torture" Test Data Log over 25 minutes:
The use of this powerful battery technology is possible because of the Gemini V-2's efficient design, and relatively low power consumption, while not sacrificing
Use of the pack in Gemini V-2 is well within the limitations of the cells. The Reduction in Weight allows for almost 2 lbs to be added to the payload potential of Gemini V-2, thus providing significantly longer flight times.
Flight time is increased to 4 hrs now, with the use of this pack! (flight time will be reduced somewhat when carrying payloads) Cost is about equal to Li-Po batteries of the same capacity, and with 300 estimated useful life cycles, This battery is also a great value!
This proven technology has already been used for years in industrial applications. Innovative design and assembly techniques provide distributed cooling for all cells in the pack, and an even flow of electricity, preventing the imbalance of the pack during discharge. Assembly of the pack without the introduction of ground loops assures that no electromagnetic induction takes place, providing clean power to the airplane without interfering with sensitive on-board electronics.
"TESLA" style battery for Gemini V-2: specs:Total capacity: 64,000mah
Usable capacity: 56,000mah
Max cont. amps: 70 A
Burst amps: 120 A
Weight: 3 kg
Charging voltage: 12.6 Minimum voltage: 9.6v
Dimensions: 200mm x 100mm x 80mm
Modular Design for Easy Assembly in the Field!
Fits in the trunk of most small cars!
What sets Gemini apart from every other UAV or FPV plane?
Check out the video below to find out!
Wayne's high quality Laser-cut Parts
Speed Assembly of your Gemini V-2!
Cold Air Cooling Inlet: Most electric aircraft models absolutely need cooling for the battery, to prevent it from overheating. It's always a good idea! For Long Endurance flights, the Gemini V-2 may not need much, but for flying at higher throttle settings, and flying with less battery capacity to increase payload, Additional air cooling will be necessary! Just don't forget to leave the air a place to exit. Another Tom and Dave Modification that will keep your components cool!
Motor Nacelles: Although the stock "profile" nacelle is by far the most practical solution, some prefer a "box" style motor Nacelle, so they just used two 1/8 inch ply pieces, instead of the 1/4 inch profile design.
Wayne designed the kit version with 2 each of the 1/8" pieces, so whether you decide to laminate them together, or build them into a box structure is up to you.
Air brakes: Gemini-V2's thick airfoil is very efficient at normal cruise speeds, and up to full gross weight. However, when the aircraft is placed in a slight dive, excess drag helps bleed off airspeed quickly. Nevertheless, many people wanted extra air brakes that could be deployed on command, and they are very useful! Tom Ethen, and builder Dave had the same idea, and they put air brakes on their V-2 airframe, pictured below.
Dave, who flies the plane, reports that they help the low speed tracking ability of the plane, and "Lock it in" on approach. They report a 25 % reduction in landing rollout distance! No pitch trim is needed when deployed! At Bearospace, we love feedback, and would love to see pictures of your air brakes and other mods.
Check out our build video for the air brakes, on our youtube channel!
Gemini V-2 Mods/Laser Cut Kit Info/Setup advice
For Advanced Builders!
Many Thanks to everyone who has purchased plans, subscribed to our youtube channel, shared pictures, contributed valuable data points or otherwise helped with this great project!
To Purchase Gemini Version 2 plans,
Just click here:
Remember that the EZUHF LRS system works best when you've re-bound it while connected to the specific Controller (such as Futaba or Taranis) that you will be using it with. Once that is complete, you may want to setup a head tracker. We are using the original Dominator goggles from Fatshark, with the head tracker chip.
The Manual can be found here:
The head tracker needs to be on channel 5, to activate channels 6, and 8 of the EZUHF system.
to do this, power on the goggle main power supply while holding down the enable button for the head tracker. the one you use to active the head tracker, and disactivate it.
It will then start a series of beeps, once, then 2 times, then 3, 4, and 5. just after it beeps 5 times, press the enable button again, and it will be set at channel 5, which activates channels 6, and 8, according to the manual.
Also connect rf module (TX module only) to the usb port, immersionrctools, make sure the immersionrctools recognizes the TX module, and make the following selections:
Select EZUHF TX module as the device you want to configure, then select the head tracking menu.
After that, select pan source 6 tilt source 8
pan destination 6 pan destination 8.
Click on the upload settings to transmitter button, and the program will after a few seconds, verify that you have re-configured the Tx. you can then simply unplug the usb cable, and install the Tx module in the controller, and try the head tracker. it should work now.
Pressing the bind button once quickly will disable, or re-enable the head tracker. kind of funny way to do it, but it’s also re-configurable to work from an rc channel, or as i prefer, from the button on the goggles.
Now try the head tracker, and see if the servos move in the correct direction. if they do not, or if one of them does not, do not try to use the RC controller to reverse the direction, as there will be no effect. plug the Tx module back into the computer with the usb cable, and make sure the immersionrctools recognizes the tx. then go back to the head tracker menu, and click on reverse next to the channel, be it pan, or tilt, that needs to be reversed. Click upload settings to transmitter, and now your servos should move in the correct direction.
More about Future Star, and the Concept behind the plane:
Future Star is an EXPERIMENTAL space access research vehicle, which has been designed to enable hobbyists to fly real mission profiles with similar components to the growing private sub-orbital space plane industry, and reminiscent of the 1960’s to 1980’s research vehicles made by Nasa, such as the early lifting body demonstrators, the X-1, X-15, and the Orbiter, better known as the Space Shuttle. The concept has been adapted so as not to need the flight control computers required by most rocket powered aircraft. It incorporates an electric power system, twin motors, and counter rotating props. This makes it a hybrid electric/rocket powered craft, perhaps the only of it’s kind.
When built according to the plans, and following the recommended control/power system setups, it has unlimited vertical performance, combined with good low speed handling and self recovery tendencies from any attitude. It is surprisingly stable in flight, and can fly hands-off. It is also very responsive to the flight controls, and can perform rolls at a very high rate, and other aerobatic maneuvers.
Future Star is not meant to be an aerobatic aircraft, and it is impractical to expect it to perform true “pattern” style aerobatic maneuvers, especially since it has no separate yaw control surfaces. Please refer to the build video on our youtube channel: FPVREVIEWS, to see the proper setup, and if there is any discrepancy between the video and the plans, follow the plans.
As an unconventional, lifting body, tandem wing canard, it has some unusual flight and stability characteristics. It has trainer-like roll stability, up to about 25 deg. in either direction, and then is increasingly resistant to roll at that point. It takes an additional, heavier, control input to push it past that bank angle, as the natural dynamic stability is fighting to maintain an upright orientation. When pushed past, it then breaks free of this corrective force, and can be rolled at a high roll rate, and fly inverted with ease. This is an intended design characteristic. The corrective roll tendency is very fast acting, because the wingspan is so short. Low airspeeds combined with an aft center of gravity can produce a slight wobble in the roll axis, however, it does not present a dangerous stability problem, and can be corrected by moving the center of gravity slightly further forward, or by flying the aircraft at a speed slightly further from the stall. When setup properly, a stall is very difficult to achieve, and the aircraft would prefer to drop it’s nose automatically, maintaining a nose up attitude, while descending. Likewise, Future Star will recover from a vertical descent by lifting it’s nose automatically, and excess airspeed bleeds off quickly.
Takeoffs without the Gemini V-2 mother ship are recommended to be done from the ground, from a relatively smooth surface. There is no nose wheel steering, so pointing the aircraft into the wind is advisable, before takeoff. It is possible to hand launch the aircraft with a side launch technique, however, it does not provide a stable launch, and often results in a wild recovery maneuver in the first 30 feet of flight, in order to gain proper orientation after the upset of the hand launch. The Ground takeoff is much more safe, and is the recommended method.
Landing is fairly conventional, however, one unique characteristic of tandem wing aircraft is sometimes apparent. That is the tendency of this type of aircraft to follow terrain curves, while in ground effect. This “terrain following” effect sometimes interferes slightly with the landing slope, and it’s good if the pilot is aware of it before flight. It’s actually a convenient feature when flying close to the ground, as it tends to keep the aircraft at a certain altitude “automatically”. So not rely on this to keep you from crashing, as it’s just a slight tendency, not a catch all for gross mistakes. approaches are best made with some power, as the glide slope is not particularly flat, and more resembles the glide slope of the space shuttle, rather than a sailplane. That being said, it is possible to land Future Star with no power to the motors, but not recommended. In fact, we recommend keeping the flights short enough to make sure that you have some reserve battery power left for a go-around. This is a safety factor for the aircraft, and also will help your lithium battery live a long, and healthy life.
Rocket Powered Flight:
Whether you get in the air from a rolling takeoff, or have Future Star carried aloft by Gemini V-2, we recommend using the electric power to bring the aircraft to a safe altitude, and in a level, or nose up attitude before firing the rocket motor. The recommended C6-3 rocket motor provides a good starting point for relatively safe rocket powered flight, while providing enough of a kick to be a lot of fun, and leave a really cool rocket plume in the sky! A few seconds after the rocket motor has burned out, it will eject rearwards, from the carbon fiber tube, and will make a loud noise similar, but not as intense, as the discharge of a firearm. Make sure that the noise will not frighten anyone in the area. The ejected rocket motor will still be hot, even after falling several hundred feet. At the moment of ejection from the aircraft is is engulfed in flames, and may even be on fire.
Always fly at a place where there is no possibility of catching your surroundings on fire. We prefer to wait until the morning after a rain, to perform rocket powered flights, even though the surrounding area adjacent to our club field has nothing that we believe is likely to burn. Be responsible and make some attempt to find the ejected rocket motor. If you have a spotter handy, ask them to watch where the rocket motor falls. It’s actually fun to find them and look at the spent motors after the flight. I collect them, and I’ve managed to find almost all of them. Ah, the smell of burnt powder in the morning!
There is room in the tail faring to add up to 5 rocket motors, and staging the motors to fire in sequence is a possibility as well as firing them all together. We can’t tell you if it is safe, but we can’t stop you from experimenting either, and we'd love to see it!
We sincerely hope that you enjoy your building and flying experience with Future Star, and hope that you can learn some very valuable lessons, while having lots of fun! Feel free to send us pictures of your finished aircraft, and we’ll consider including the pictures in a future video. You can send pictures to my email directly: email@example.com
It’s really cool to be able to play with this air launch / re-usable / rocket-plane technology, and not have to spend many millions, or billions to do it! I hope this design provides you with a platform for your own experimentation, and as always, I’d love to see any modifications that you make to the design.
The Future Star concept has the potential to be powered by more advanced electric, and rocket (liquid hydrogen, etc.) propulsion systems in the future, and could be scaled up to fit underneath larger aircraft. Handily, the concept, scaled up, could fit under existing aircraft, such as a Cessna Caravan, or other aircraft, to be air launched, without need of a specialized mother ship, such as is needed by concepts such as spaceship one, and two, by scaled composites.
How far could the concept, potentially, go?
Air launching of space vehicles can allow for more flexible takeoff locations, such as flying from a normal airport, without the need for a launch complex, and the launch point can be flexible as well, even launching from closer to the equator, needing less energy to get into orbit. It also gives the rocket powered space vehicle an altitude advantage over ground launches. The Future Star concept, incorporating electric propulsion, further reduces losses, by enabling the rocket motor to be fired, while in a vertical, climb, therefore eliminating the typical maneuver, where the rocket plane is forced to fire it’s rocket motor, while in a nose down attitude, burning precious fuel, while conducting a pull-up maneuver to get oriented into a vertical position. The electric motors could also help propel the vehicle to an additional height before the rocket motor is even engaged, enabling even more attitude potential. The mother ship could be thought of as a first stage, and the electric propulsion of the Future Star as a second stage. Future Star’s rocket motor could be fired, or several of them could be fired in more stages. Even if it was not practical to go all the way to orbit with Future Star, The large payload bay in the belly could be opened, and an internal rocket, with it’s own payload could be deployed, at the Future Star’s apogee, delivering small payloads to orbit with a very high degree of re-usablilty. This would solve many of the problems with re-entry, as future Star may not actually leave the atmosphere. Since much of the propulsion is electric, it would be a more environmentally friendly way to getting small payloads into orbit as well. Payloads such as teddy bears, of course.. Bearospace!
If Future Star does nothing but provide you with a fun RC plane to fly on the weekends, and inspire you to learn more about the new space technologies which will become common-place in the future, It has done it’s job, and we are happy to be a small part of that!
Laser Cut Kits Available!
Contact Wayne (Flying Squirrel Models):
If you're interested, You can build your own "Tesla" style battery by watching our build video, or contact us for pricing and availability!
Laser Cut Kits Available!
Contact Wayne (Flying Squirrel Models):
First Prototype-was so fragile, but flew:
Wayne McNab, Owner of Flying Squirrel Models, on Pender Island Canada, produces the high quality laser cut kits for V-2.
The fuselage kit, Short wing kit, and tail feathers kit are available separately, or can all be shipped together. This is so that you can decide which major assemblies you would rather have the kit for, and which parts you may not mind building from scratch. There is also an option available for a supplemental parts package which reduces the amount of dihedral in the wings. A modified motor nacelle (lower thrust height) is supplied to match. This is a useful mod, when the aircraft will be used in gusty wind conditions, and/or flown mostly with autopilot.
Hardware, such as landing gear, control horns, hinges, carbon fiber parts, etc., are not supplied with the kit. You will need some supplemental materials. The materials you will have to source separately are not included in the kit, as their size would greatly increase the cost of shipping. An info package With all pertinent information about the kit, including pricing, and a supplemental parts list is available free of charge by contacting: firstname.lastname@example.org
You can also use the same email contact for Wayne, if you have questions specifically regarding the kit version during the build process.
The Kit Does not include the plans for V-2, as those are sold separately here on the website. Just click on the BUY button directly above.
Payment to Flying Squirrel Models is via Paypal as well.
Bearospace Does not receive any compensation regarding the kit sales, however, we are very glad that Wayne is producing the kits as a time saving resources for our customers.
Wayne has re-engineered the V-2 structure somewhat, to optimize it for the production of the Laser Cut kit, as the original design design was intended for scratch building. Weight of your build is dependent on wood selection, and build methods. Nevertheless, the kit version usually ends up weighing slightly more than the scratch built version. It is also more robust, and we recommend the kit version for commercial applications for this reason. Since Wayne has invested so much time (hundreds of hrs.) in the CAD design work, and the laser cutting machine to produce the kits, he has opted to retain the laser cutting files. We're sure that everyone can understand why.
Just to give you an idea of what a great value the kits are:
When we, here at Bearospace, want to build another V-2 for a customer, we order the kit from Wayne at the same price you pay... We are sure that you will find that the kit is very well thought out, of a very high quality, and a real time saver!
Future Star FPV setup!
One micro board cam, a wireless video tx/rx, a 5v regulator, and an inline LC power filter. Wired into the balance lead of the battery, this was an easy installation!
As Future Star only weighs around 2 lbs, The Captive Carry flight test went very well, and presented no problems. A few minor modifications were necessary to V-2 in order to safely carry, and launch the rocket plane.
The release Mechanism on Future Star is designed to work with a medium size nylon "Zip Tie", or "Cable Tie" as the link between the two aircraft. This allows several key characteristics to the nature of the coupling between the two aircraft. it allows a loop to be formed with the tie, that lets enough space between the aircraft for you to reach in and guide the tie into place inside the release mechanism on Future Star with ease. It is then tightened, securing the aircraft together with a light pressure between them, keeping the joint reasonably firm, so that no oscillations occur during captive mode. Then the servo for the release mechanism in Future Star pulls it's pin, and releases. The low coefficient of friction (slipperiness) of the tie, allows the pin to pull past the tie easily, without getting caught, releasing the rocket plane safely.
A wire brace was used, on the front of the main landing gear, visible in photos, and videos of air launch. This helps prevent the Canard, or forward wing of Future Star from getting caught on the main wheels of the Gemini V-2 mother ship. From the footage, we were able to determine that the canard had some clearance anyway, during launch. In fact, it never contacted the protective wire guard brace, although we recommend integrating it into any aircraft that will be launching Future Star anyway.
In Case the Future Star's Rocket Motor were to fire accidentally, while still attached in Captive Carry Mode to the Gemini V-2, We fitted the lower rear Fuselage of V-2 with a Silicone sheathed flame deflector shield. We made the base using 1/8 inch ply, and a store-bought silicone hot plate/table protector, cut down to match the rectangular shape of the plywood backing, but slightly overlapping it. They were glued together with CA glue, and Ca accelerator was used to help the glue foam up, and fill in the gaps.
This was attached to the airframe with 4 servo screws, so that it can be removed easily when not needed.
Lastly, we fitted an inverted V shaped chock to the underside of V-2, on the centerline. It was made from 1/8" plywood, and the underside was lined with foam rubber, to prevent scratches to the Future Star finish. This V-shaped chock keeps Future Star aligned with Gemini in flight, to maintain the best possible aerodynamic properties during the Captive Carry phase. See picture below.
The only permanent modification to the mother ship was to drill two small holes in the underpart of the fuselage, directly above the release mechanism. The cable tie goes in one, from the inside, and then up the other one, back inside, where it is connected, so that the "tail" of the cable tie ends up on the inside. The cable tie is then tightened moderately, and is ready for takeoff. After the flight, the cable tie is cut, and discarded. The cable tie and the rocket motor cartridge are the only parts that are not re-usable.
So much for complete re-usability....
Canard span: 550mm
1/1 thrust to weight ratio with economy power package
1.5/1 thrust to weight ratio with premium power package
Future star is built from :
1-16 inch balsa sheet,
1/4 inch balsa sheet,
1/8 lite ply
3/8 x 3/8 balsa stock
1 strip of 500mm X 7mm X 1.2mm carbon fiber (bracing for the inboard vertical tail/motor nacelles)
Economy power setup:
2 Silver monster 24 gram 1700kv 2712-12 motors from lasertoys.com(15 dls)
2 counter-rotating 8x4 multi rotor props
2 20 amp Multistar or Afro ESC’s from hobby king.com (12 dls)
and one 1300mah 40C - 2200mah 25C 3 cell batt
Premium power setup:
2 E-flite park 370 1360kv motors(40 dls each)
8X6E and 8X6P APC thin electric counter rotating props from readymaderc.com (the P designation is for "Pusher")
Castle creations Phoenix Talon 25 brushless ESC with BEC (one BEC disconnected, the other powering the receiver) (34 dls each)
2 micro servos, I used airtronics metal gear 94557 (or other metal gear micro servos)
1/2A control horns from dubro (uses outer hole)
it does need a computer radio with elevon mixing, end point adjustments, and expo settings. (not a big deal these days)
Flight time: 15-20 minutes (not bad for a high performance model)
Lots of room in the back for rocket motor/motors.
Weight (bare configuration, without accessories): 810 grams
Control setup: End point adjustments on servos set to 80%
Expo on roll axis set to 60%
Expo on pitch set to 20%
Fitting of rocket motors of various sizes. It would be possible to fit a cluster of up to 5 small rocket motors to the rear fuselage area, for experiments in multistage firing.
Addition of a fly-by-wire flight controller to augment stability in rocket powered flight, and during advanced maneuvers.
additional control surfaces on the canards, and pivoting the rudder-vators, to add vectored thrust, for "Super-Manueverability".
Air brakes on top, and bottom of fuselage near the rear, for vertical descent, and to control airspeed during release from high altitudes in thin air, such as from a weather balloon, or Air launch from Gemini V-2.
The plans could possibly be scaled up or down to accommodate various needs.
After reading documentation several times it became apparent that there was more to autoland than any of the flight modes.
There are several issues, in using autoland, mostly due to sensor limitations.
To start with, a way to calibrate the altitude estimation in flight will be necessary in order to have the plane flying at the proper altitude when starting the approach. The last waypoint in the air ( before the land waypoint at the beginning of the runway) is the point where the pix hawk switches use of the barometer or GPS , (whichever you have selected in parameters)
To using the laser rangefinder.
There will inevitably be some difference in the two altitude estimates, and the corresponding altitude change when the last waypoint is reached is referred to in the documentation as BARO BUMP.
The degree of BARO BUMP will depend on several factors and will be different if you are using gps for altitude estimation in flight or the barometric sensor.
Assuming you are using the barometric sensor, you should be aware that the sensor itself is subject to drift, however this is a minor consideration.
A larger consideration is the changes in barometric pressure that occur naturally due to atmospheric conditions. If the flight is of short duration, the error in altitude estimation using the barometer is likely to be small, however changes in ambient air pressure can change abruptly, so those changes should be taken into account when planning the flight approach, to provide adequate clearance to obstacles on the approach path. A large BARO BUMP, (or one which occurs at the beginning of the approach, where the last waypoint is relatively close to the land waypoint )
Can force the plane to nose down when the glideslope is recalculated at the last waypoint. It takes time for the plane's airspeed and trajectory to stabilize on the approach after this upset, and depending on how closely the requested glideslope matches the achievable glideslope, there may not be time or distance for the plane's trajectory to stabilize before the time to flare or altitude to flare is reached, resulting in an overshoot of the intended landing area, and an over-run of the runway. Simply setting the land waypoint back further will not achieve consistent results.
A permanent solution to the inconsistencies of the approach due to BARO BUMP will involve a recalibration of the barometer in flight, shortly before the landing.
One way to do this is to use a ground based barometer as a reference, comparing and recording the readings between the two, then uploading the offset differential in flight before the landing. This is done via telemetry, and there is a provision for it to be done automatically by using mission planner.
This concept can also be utilized by using differential GPS, a special type of GPS, where one unit stays on the ground and provides data for the airborne altitude correction to be made via telemetry.
The problem with either of these solutions is that they rely on the telemetry link in order for the airplane to land safely and consistently.
A better solution would be for an onboard calibration of the altitude estimation based on laser rangefinder data, as part of a mission, by flying the plane over the runway ( a large flat area) and taking one or more readings with the laser rangefinder at this point to use for reference. This can be achieved using existing sensors already on board the aircraft, and does not depend on a telemetry link or purchasing of additional ground based sensor hardware.
As such, it would be the preferred method, especially for using auto landing after a mission lasting several hours, where barometric pressure can easily cause errors in altitude estimation of over 20 meters or more over a one or two hour period.
Using a GNSS GPS can also help, however it would appear that even these units can have large errors in the vertical plane, making their use for altitude estimation by pix hawk unsuitable unless the approach is a very long one.
Using a long approach ( and consequentially a high starting point for the approach) can be an acceptable solution for some users, However this solution is dependent on the terrain elevation and smoothness on the entire approach, as the pix hawk will be using the laser rangefinder exclusively for altitude estimation during the entire approach.
If there is a significant dip or rise in the terrain along the approach path, or obstacles close by SUV as trees, this is no longer an option for a safe, consistent auto landing.
Even a vehicle parking on the approach path in this case is enough to create a significant inconsistency in the altitude estimation, and ruin the approach.
Another important parameter is the prioritization of airspeed vs precision of the landing. It's important to realize that if you prioritize precision, the plane will still try to use throttle to maintain airspeed, so the prioritization of precision simply separates the control of throttle and pitch control.
( having these coupled, or prioritizing airspeed can cause a pitch and speed oscillation, depending on the slew rate and damping of the throttle control) Using the throttle only for airspeed at the second only to maintain the glideslope elevation, until the land waypoint is reached, at which time the throttle is set to zero ( if the pix hawk considers the landing a success) and the flare is initiated.
The flare distance will depend on the height that the flare is initiated, the centidegrees of pitch that you have selected, the airspeed when crossing the landing point threshold, and the aircraft flight dynamics. Some factors that can change the flight dynamics are the aircraft weight and coefficient of drag due to choice of landing gear, airbrakes size, and the drag from any external payloads being used.
It's important to complete all initial testing and or changes related to autoland in no- wind conditions, as the accuracy of autoland is usually improved with the presence of a headwind, and the rollout distance is also decreased. If autoland parameters are first tested in even a slight headwind, subsequent use of these parameters in zero-wind conditions will most likely result in overshoot of the landing zone and/or over-run of the runway rollout area.
It's best to do the testing first in no wind conditions then gradually fly the same auto landing mission with ever increasing headwinds, then ever increasing crosswind conditions to check for consistent results. There will likely be some changes in the landing but the important points to look for are proper airspeed throughout the approach, a safe looking flare with smooth touchdown, and stability of the aircraft on the wheels after touchdown. The line from the last waypoint to the landing waypoint is extrapolated beyond the land waypoint, and a compass heading is followed, so some deviation in heading during flare and after touchdown is expected during a crosswind condition, but should be within safe limits.
Tuning of ground steering is a must if you find that the plane is weathercocking significantly during the landing. Moving the main gear slightly back to put more pressure on the nose wheel can also help, however you must be aware that the aircraft has a maximum crosswind component which can not be exceeded under any circumstances.
Tuning of the nav L1 loop, or nav tracking loop can also help the accuracy of auto landing, due to the increased accuracy of tracking on the lateral plane during the approach.
If you see something that can be improved, or that we are doing wrong, please let us know, as we are constantly improving our product!
you can email us direct: email@example.com
or go to the contact page of this website!
Thanks for all your assistance and support of the project!
Testing your EZUHF or other LRS UHF Tx output power level using the ImmersionRC RF POWER METER:
First, make a power lead with a 2S, 3S or 4S lipo. use a barrel connector. It's the same connector used to power the External TX UHF module. Center pin is positive, and outside of barrel is Negative. Next, connect the Attenuator (ringed attachment) directly to the meter, then use the extension to connect that to the output of the TX module that you wish to test. Do Not turn on the TX module unless the attenuator or antenna is attached, as damage can occur.
Settings to use once the unit is powered:
Fine Att. 0.0db
Now, make sure that the attenuator, and meter are attached to the output of the TX module, then turn on the module.
"max" - should read near the spec Mw for the power level that the unit is switched to.
for example: max 194.96 for EZUHF JR Module
"Min" will read 0. this is normal for a spread spectrum system.
When the high power switch is activated, the reading should go up to an appropriate level.
for Example, the EZUHF JR module in high power;
max 429.39 was the reading of mine.
I also recommend a range test as per the manual, and use of their Frequency analyzer to locate sources of on-board noise in the systems on board the aircraft. I made a Video specifically about that issue and some other issues that you will want to check out regarding the performance in terms of range:
Suitability of the Gemini V-2 for Autonomous Mapping Missions:
The Gemini V-2 is an endurance optimized airframe, so has many uses that most aircraft that are distance optimized do not work quite so well for. to simply cover a large area, it’s important to be able to have the best distance, but there is a problem of the limitation of the sensors, namely, processing power, and resolution. unless the aircraft is to fly at a higher altitude, and use optical zoom, (not such a good idea, as atmospheric contamination becomes a negative factor), the aircraft must slow down, and fly lower, to allow the resolution, and enable time for the camera to process the image, before taking another one, without having a gap, and missing something. That’s what people are attracted to the Gemini V-2 for mapping missions, even though the theoretical distance that it can cover is not as much as some other airframes. That combined with it’s large internal volume, and ability to lift larger amounts of weight, make it a good choice for high resolution mapping.
The option for less dihedral is useful if the aircraft is to encounter significant wind shear and will be flying mostly autonomously. This way there is less roll coupling with yaw, or control surface movements, when the wind shear is encountered. (the autopilot , if tuned properly, should be able to overcome it, or coordinate it, depending on the system type, and stabilize the aircraft. If not tuned so well, it is more likely to be problem.) the decreasing of the dihedral also lessens the ground clearance of the wingtips on landing. (bad landing)
Experimental Space Access Research Vehicle / Park flyer...
Rocket Motor Ground Testing Video (In Vehicle)
You may have noticed by now that Gemini, besides being optimized for stable handling, efficiency in long duration flight, are also optimized for maximum separation of the components that make RFI and EMI from the sensitive components, such as the UHF receiver. That makes the Gemini series of aircraft the best in their class in terms of potential range and distance, while transmitting live video, and maintaining robust operator control!
Heavy Duty Landing Gear:
Requested by our friends in Norway, for their "Africa" Project, This Mod adds ground clearance, and provides less flex in the landing gear to protect external payloads from landings on un-prepared terrain. This particular V-2 build used 4 inch "Tundra" style wheels to further it's rough terrain capability.
An extended nose fairing completed the mod.
Silicone "hot dish pad" cut down to create a heat shield. This would help protect Gemini V-2 in the unlikely event that the Future Star's rocket motor would accidentally be activated in-flight.
Gemini FPV setup :
motors E-flite power 15 950kv
props 13X8 and 13X8p counter rotating inwards at the top
esc’s phoenix edge 50 amp
2 video systems powered by 2 separate heavy duty LC filters
video transmitters 2x race wood 800mw red label taiwanese from dronesvision.net. (on wingtips)
700tvl fpv cameras. one for pilot, and one for observer
GWS1T360 deg. sail winch servos for pan on both.
Ezuhf 8 ch diversity receiver with dipole antennas horizontal and vertical) for pilot’s control system set to 435-437mhz.
Dragonlink V-2 control system for observer functions
MFD antenna tracker (extra channels version) with 1 13db patch antenna for pilot’s video and 13db yagi for observer video
futaba 8 ch. radios with adapted uhf modules for transmission of control signals.
Control surface throws, and advice for first flight:
The control surface throws are not critical, as they are with many sport models. We always like as much throw as we can practically get from the rudder. The ailerons and elevator are more sensitive, and on V-2, and it’s best to limit them to about 70% of their max travel. We do not use any differential on the ailerons, but it would not hurt anything either. We use some expo on the ailerons, and the elevator, but not the rudder. We always mix rudder in with the aileron control, to eliminate the adverse yaw effect. it takes quite a bit. anywhere from about 60% to about 85 % should do the trick. If you do not have enough, you will notice in the camera footage, that the nose wiggles sideways when you bank. Start With some, at least 60%, and look at the footage, Adjust the mix accordingly, until it’s not perceptible.
The aircraft does not need much control input in flight, and it’s not sensitive to control input. We think you’ll find that it’s very forgiving.
The most important part of all of this, is the rudder mix. Use the aileron channel for master, and the rudder channel for slave.
We designed the aircraft for all servos connected with roll, and yaw, including the nose wheel servo, to all operate in the same direction. This lets them all operate off of the same channel with Y connectors, if the radio being used is limited to 3 channels for primary aircraft control. The throw of the rudder could be adjusted to give the proportion of mix from aileron to rudder, and it could also be used simply to free another channel for some other function, such as pan for an FPV camera. The only function lost would be the ability to slip the airplane, for steeper descents, and crosswind landings.
During flight, We rarely use the elevator control, and merely steer the aircraft with the right stick, that is the aileron control, with rudder mixed. We occasionally make an adjustment to the throttle setting to climb, or descend. We usually only use the elevator for rotation on takeoff, and flare for landing.
It is possible that some trim may be needed if the airplane wants to turn to one side, or another, and the natural response is to make trim adjustments to the ailerons. However, it is far more responsive in most cases, to use rudder trim to correct this tendency. It is more likely that it’s a yaw problem, than a roll problem, so always try yaw trim first, before trying roll trim.
Elevator trim is rarely needed, and does not seem to make much of a difference in small amounts, as the stability of the aircraft in pitch is very high. You’ll find the aircraft to be much easier to fly than most trainers.
If you need to kill glide path, or find yourself too high on approach, the aircraft responds well to a slight dive in order to bleed off altitude. In the shallow dive, the thick airfoil serves well to manage the airspeed. We have not felt the need for flaps or brakes, when using this approach, although their use would be beneficial. We also like to use the ESC’s programming mode to allow the props spin freely, as that adds to the aero-braking effect with the motors turned off, or at a very low throttle setting. This makes it easier to get down to the ground in a controlled manner with power off. The aircraft tends to float down the runway a bit on flare, as you can see in the videos, but does not travel that far in the nose up attitude before settling onto the runway.
The aircraft is optimized for fairly slow flight, and there is not much benefit to pushing it around the sky at higher speeds.
I wish you the best on your flights, and if it’s not too much trouble, or distraction, take pictures, or maybe video of the flight, to share on youtube? I'd would love to see!
Be sure to double-check the CG, and make sure the battery is secure. Make sure the pushrod for the elevator in particular is robust, and won’t be compressed, or bent.
You can do a quick load test on the wing, by suspending the completed plane from the wingtips, to make sure the wing structure is sound.
Balsa/Wood for Gemini Build:
There are several sizes, and types of wood that are used for building Gemini, and there are many options for material size, and thickness, from which to make the parts for assembly. Let me start out Saying that the best option for most builders is the laser cut kit, as the wood is good quality, being pre-screened for use by Wayne. Sub-par wood is not included in the kit, and is discarded. some additional wood is required to finish the kit, and that is clearly laid out in the info package for the kit, which is provided free of charge.
Even if building the scratch build version, it’s probably not such a good idea to order just enough wood, as some of the pieces are likely to be less than ideal for a certain use anyway. There are also variations of building methods that make determination of exact quantities difficult. In any case, we recommend buying more wood than will be needed.
We order wood from Tower hobbies, branded with their name, and we find it to be overall good quality. The price allows me to buy excess wood, which can be used for optional accessories, such as camera mounts, etc. that we may want to build later. Buying this way allows for good wood selection, and enough left over, for actually less money than we would have spent buying the wood at a local hobby shop, or even buying from an online vendor in the exact quantities.
Tests have shown that the front wing, (canard) does not hang up on the wheels during a "normal" release. Nevertheless, It's a good idea to fit a wire brace to ensure that it can't happen.