X-20 Dyna-Soar with titan booster....

Discussion in 'Rocket Boosted Gliders' started by burkefj, Nov 3, 2014.

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  1. Dec 16, 2014 #31

    burkefj

    burkefj

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    This is a DX7 and am using a 4 ch receiver built into the model already that I'd like to not change.
    Currently I'm using the flap switch to input elevon offset for glide and boost setting. By mixing elevator to elevator with a negative % and mapping that to the flap switch as well, I can get reversed movement on the elevons on my boost position. However due to the mix it doesn't give me full deflection on that setting but it might be ok since that will be at higher speed and throw required won't be as much.

    It's not the offset I need, i can do that, it's just the direction change mapped to a switch setting, since it has to change for a different flight mode.

    Basically, when on the stack in boost mode, elevons are neutral and direction is reversed on pitch only.
    In glide after separation, there is up trim on the elevons and direction is normal on both pitch and aileron.
    I talked to one of the spektrum folks, they though on a dx9 it might be possible.

    Frank

     
  2. Dec 17, 2014 #32

    tab28682

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    Probably could do it with any of the Spektrum TXs that offer programmable flight modes.

    Good catch on flying the stack as a canard with opposite to "normal" pitch deflections during boost and converting back to normal elevons after release.
     
  3. May 27, 2015 #33

    burkefj

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    Getting close, now that I've flown my fullscale Hellfire foam rocket successfully, I'm going to try to fly this by mid June if weather cooperates and I get a good launch site. My 5# Hellfire flew to 650 feet on an H-135, I'll fly my Jupiter C on an H-128(it is 3.5#) and see how it's boost looks. I'm thinking I have an H-115 which should be a good inbetween motor, as this is 5# but I want to keep it to around 4-500 feet max so I can see the glider...But this is a sparky motor, so field might not be suitable and I need to keep it off the blast pad so that I don't get a bunch of sparky backblast melting the skin.

    Frank
     
  4. May 28, 2015 #34

    georgegassaway

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    Wow, another neat thread I missed. Great project, to make it that big and light.

    For the reversal of pitch control for boost, there is a trick that I learned from Don Edberg, who wrote several books on how to use various Futaba transmitters and such. I had a Futaba 8U, and needed to reverse rudder control for boost. It was for my shuttle which uses rudder for turning and not mixed elevons (elevons moving only for elevator pitch. The rudder for steering makes an orbiter handle very smoothly for turning, though I found out the hard way to only make the lower half of the orbiter rudder to move, not the full height). On boost when attached to an ET/SRB stack, or on a special piggyback rocket, left rudder would act like an aileron and give me right roll, very bad. I had to find a way to reverse the throw for boost (left stick causing rudder to move right to cause left roll.) then move the correct way for glide.

    I e-mailed Edberg for help, I had his 8U book but did not see how to do something like that. He said to first mix rudder into rudder at -100% (negative 100%), which when active would mean the rudder servo would not move at all. Then add a second mix of rudder to rudder, again at -100%, which when both mixes were active would make the rudder move the opposite way from how it moved with the mixes off. Works perfectly for that, and probably would for your need for pitch reversal.

    That double-negative mix of same channel mix into itself solution was not unique to the 8U, that basic idea works with any transmitter that has a sufficient amount of mixing options. I do not know the DX-7 enough to know if that is practical or not.

    Of course it sounds like you had a workable solution a few months ago, but wanted to pass that along in case it was useful for this or some future project. I have used that double negative self-mix trick for other things since.

    - George Gassaway
     
    Last edited: May 28, 2015
  5. May 28, 2015 #35

    burkefj

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    George, that was very useful. I did figure out mixing -125, -125 on the flap switch, but instead of your case where you got 0 movement, I got about 25% movement, which makes sense.... changing to -100, -100 and adding that second mix of -100, -100 got me the full 100% movement in the opposite direction. Thanks for that.

    I know I should take this in stages, I've got the glider flown standalone with an E-6 and have a good glide trim. And I should fly the booster standalone and make sure the everything works as it should before putting the glider on, however I'm afraid it might get damaged on landing or boost and I'd never get the full stack flown, so I may just suck it up and try the full stack, in any case I may get a few photos, or a funny video....

    Frank
     
    Last edited: May 28, 2015
  6. May 28, 2015 #36

    georgegassaway

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    I'm glad it was useful. Now ironically for boost you may not want to have the same throw (reversed) as you do for glide. A canard set-up like that, and a high speed boost, is likely to be sensitive in pitch. But it is so good to have more throw than you need, and dial it down (low rates), than not have enough.

    As for testing, the biggest unknown will be what happens with the X-20 on top of the booster. When I was working up my 2.6" model, I made a very very crude 1" boilerplate, adding noseweight to get the CG where I thought it needed to be, and flew it to see if it was stable. It was. Since you have that info on where the CG should be, you do not need to test for that if you use the same proven CG if it is scaled right (and looks like it is).... and indeed a test flight without the X-20 would not test for stability anyway.

    I figure then the main thing you'd get out of testing the booster only is to confirm that the recovery system ejects and deploys properly. If you did test the booster alone, you'd probably want to simulate the mass of the X-20 so that the boost velocity would be sort of close, otherwise it would boost faster and possibly over-stress something.

    Anyway, again the biggest thing will be what happens with the X-20 on top. So if you think the recovery system will eject and deploy reliably (possibly ground based ejection test without X-20?), perhaps not test the booster only and go right to an all up flight.

    I do wonder, is the mounting method of the X-20 sitting on top secure enough, so that the X-20 won't pitch or wiggle any in relation to the booster? The more it can wiggle, the more of a problem it may have with pitch control on boost as it will try to "flop" one way, then when you correct it with elevator the control forces could make it "flop" the other way.

    On my 2.6" model, I had a pretty good method to keep it from wiggling, but I was still concerned that it might have some minor pitch up or pitch down (elevons were held parallel for boost). So I built the Titan-II with the fins skewed about 2 degrees to make it do a slow roll to even things out. Also, the twin D12 mounts were skewed a bit to help make it roll slowly as well). Although on the actual flights it seemed to have a slow axial roll, not a barrel roll, so the roll probably was not needed. Anyway, I mention that as something you could consider, not on the Titan now, but perhaps give the X-20 some aileron on boost to help to average out any pitch problems. Perhaps not at first, but as an emergency back-up option if it starts to pitch back and forth and you're having way too much trouble trying to keep on top of it (There's been plenty of R/C RBG's I've had such moments with).

    Wonder if you might mount a small keychain type camera on the Titan, pointed up, to show what happens with the X-20 during the boost and sep?

    - George Gassaway
     
    Last edited: May 28, 2015
  7. May 28, 2015 #37

    burkefj

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    Yes, I was concerned about too much throw on boost, but I'm pretty quick on the sticks and seem to mentally damp out pretty quickly so I'd rather have a little more than not enough. Since it will be nose heavy with rocket stability margin, not rocket glider stability margin, I felt that the small movement I had wasn't going to be sufficient.

    I've compared my CG setting to your drawings you used that I had found and it is pretty close to a similar point, and openrocket seems to agree pretty well.

    I've done an in house ejection test with the glider attached and it ejected and blew the glider off, as well as just blowing really hard on the motor mount and it will blow the piston/cap out and push the glider off.

    I was worried any roll in the system putting too much strain on the glider. Again, the glider is very light weight construction, I'm afraid if I put any roll input it will put torque on the mounting rods and do something bad, so I'll probably just try to damp out any severe pitch and let it alone otherwise.

    I do have a keychain camera, I'll try to remember to attach it.

    As for wiggle, there is my catch 22. I've got about 1/4" of play front to back(not side to side) at the tip of the model compared to the base(1/4" in 30" of length), so not much but some. If I have anything tighter, I'm afraid it won't separate smoothly. Remember, this is a foam model, so the piston/cap needs to push gently on the base squarely to push it off the rods. I couldn't figure out a good way to use couplers and attach it at the base to the foam without adding a lot of tail weight. If something binds and the ejection is stout, it might just crush the base of the glider as it blows the piston/cap/chute out...Or flight loads may rip the aluminum guide tubes out of the model...

    I think in the end the risk of damage during landing/flight of the booster only is high enough that I'll probably just fly the entire stack and see how it goes. This is the first large rocket I built using depron, and it is lighter construction than I used on my Hellfire and Jupiter C(I used four full length longerons notched to the centering rings, and four 1.5" wide longerons that are at the surface to support the skin that don't go all the way to the motor mount. This means the booster isn't as stiff as the Hellfire and Jupiter C. So, will it buckle in flight, that's always a concern as well especially if it pitches hard due to the glider. Like I said before, there is a lot that can go wrong, even though I think it is desiged for the intended loads.

    Frank
     
    Last edited: May 28, 2015
  8. Jun 8, 2015 #38

    RocKiteman

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    NICE project....
     
  9. Jun 14, 2015 #39

    burkefj

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    Flew at Dayton Washington today. I've haven't slept for about a week thinking about all the potential things that could go wrong and what to do to avoid them. In the end, it was a picture perfect nominal flight, no damage recovery of the booster and nice glide recovery of the DynaSoar...

    I ordered two 6' lengths of rail and three splice plates, made a 1/2" od stinger to go into the quad pod head and made an adjustable standoff that mounts to the rail to keep the tail from melting from any back blast. I brought a ladder to arm the electronics once it was ready, but I was barely able to reach it....George Rachor and my son Max helped out with everything, George even standing by the rocket holding it from blowing around in the wind till we got a lull. I had to press the launch button and drive the rocket/glider but it turned out to be a non issue.

    I chose an H-97 which had a nice slow boost, not a bobble at all, once I saw it was moving slowly and arcing away from the flight line, I gave some up elevator which did straighten it out some, but was definitely not stressing the airframe. No roll. Ejection via the altimeter pushed the glider straight ahead and away from the booster and I transitioned to glide. Since there was about a 6-7mph headwind it didn't penetrate much but it was very controlable. I'm so pleased that I tried this and that it worked out so well. I did get some onboard video, you can see the bottom of the glider and then see it fly away, then see the ground and chute as it opens. I'll also post the flight video.

    Frank
     
    Last edited: Jun 14, 2015
  10. Jun 14, 2015 #40

    aerostadt

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    Another terrific project, Frank! I can't wait to see the video. It would be nice to see the pictures of the lift-off. I have noticed the same thing as you that some of the bigger complicated flights are not relaxing the week before the first flight. So, you were actually providing some guidance during lift-off. This must be more complicated than a regular rocket glider, because the elevons are so far forward on the total stack.
     
  11. Jun 14, 2015 #41

    burkefj

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    Yes, the elevons have to be reversed using mixing when it is mounted on the front of the stack, and then when I switch to glide it goes back into normal elevon deflection movement, worked like a charm. You don't see much movement of the glider before release, you can see it move just before release, I think because I was holding back stick to keep the rocket straighter, and then release before ejection so that there wasn't an aerodynamic load making it biind on the guide rods...at least that's what I was trying to do.

    Here is a video showing the construction, flight and onboard video...

    Frank

     
    Last edited: Jun 16, 2015
  12. Jun 14, 2015 #42

    tab28682

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    Frank, that was simply awesome! Well done.
     
  13. Jun 14, 2015 #43

    georgegassaway

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    WOW, great flight Frank!

    And of course, great designing, building, and engineering to make it all work so well.

    - George Gassaway
     
  14. Jun 14, 2015 #44

    TheTellurian

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    +1 Just great!


    Richard

    Ps Just read the Jupiter C and Hellfire threads, Frank your having way too much fun! :cool: Carry on sir.
     
    Last edited: Jun 14, 2015
  15. Jun 14, 2015 #45

    AstronMike

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    Most excellent, Frank!!

    From start to finish, this had to one heck of a 'grey hair' inducing project, so glad to see it ended up so well!! Perfect boost, initial motor choice, and I'm suitably impressed by how well the glider portion did. Now, an I205 in this......
     
  16. Jun 14, 2015 #46

    Leo

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    Nice one!
     
  17. Jun 15, 2015 #47

    burkefj

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    Um, I205, maybe not! If you look at my youtube video of the 5# hellfire flying on the i-205 it is way, way to fast for this model, and would shred the glider, this is a good motor choice and anything over 400-500 feet and the dynasoar is getting pretty small at 30" long to see/steer...

    Frank

     
  18. Jun 15, 2015 #48

    burkefj

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    Thanks all, I'll be flying it again next weekend in Pasco Wa if all works out, probably bring my Titan II, Jupiter C and X-15 rc rocket glider.
     
  19. Jun 15, 2015 #49

    rharshberger

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    Hope it works out, looking forward to seeing some of these models live and up close.
     
  20. Jun 15, 2015 #50

    burkefj

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    Here are some still shots before and after flight from George Rachor

    V__078E.jpg

    V__C935.jpg

    V__C3F8.jpg
     
  21. Jun 16, 2015 #51

    burkefj

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    Here are some flight stills...
    I built a new custom pad from 3" black abs sewer pipe with a 10 foot leg span, that takes the 12' rod right at the base, so I won't have to use the ladder to arm the altimeter. The legs screw into the base unit for easy transport.

    MAH00032(4).jpg

    MAH00032(5).jpg

    MAH00032(3).jpg

    MAH00032(1).jpg

    MAH00032(2).jpg
     
  22. Jun 16, 2015 #52

    burkefj

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    A few more from the onboard camera

    x203.PNG

    x201.PNG

    x202.PNG
     
  23. Jun 17, 2015 #53

    Jackball74

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    AWESOME!!!
     
  24. Jun 17, 2015 #54

    burkefj

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    Thanks George, and I appreciate your forwarding your passdown on the mixing to increase the movement, i believe that helped on boost.

    Frank


     
  25. Jun 17, 2015 #55

    burkefj

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    I made a new launch pad using 3" abs piping, with screw in legs, it gives me a 10' footprint and lowers the model so can arm it easier. I also made a new standoff that has a 1/4" hole, and I've installed a 3/16" carbon rod on the bottom thrust plate, when you sit the model on the standoff the rod goes into the hole and will prevent wind from trying to rotate it on the rail and damage the rail button mounts.
     
  26. Jun 18, 2015 #56

    dave carver

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    Superb :) Congratulations on a perfect flight.
     
  27. Jun 21, 2015 #57

    burkefj

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    It wasn't a fluke, I had two more flights today, one perfect on an h97, one on an h115 dm that was a little faster than I liked, but no issues, other than one of my stick on nose weights came loose when the glider ejected and it flew tail heavy, because it was, but I got it trimmed ok and landed fine.

    frank
     
  28. Jun 21, 2015 #58

    burkefj

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    Photo of the standoff and locating pin.

    Pin is attached to the rear thrust plate, the bottom rail button block sticks down about 1/2" and is attached to the thrust plate as well, that's why there is a gap between the thrust plate and the standoff, it's hard to see the rail button block on the right, but you get the idea. Because the fins and glider wings are so big, and the rocket so light, wing gusts want to move it around on the rail.

    WP_20150620_004.jpg
     
    Last edited: Jun 22, 2015
  29. Jun 21, 2015 #59

    rharshberger

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    I watched both of Franks flights today, both were absolutely awesome.
     
  30. Jun 22, 2015 #60

    burkefj

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    Pad worked great as did locating pin to keep the model from moving on the pad and damaging the rail button attachments.
    I downloaded the altimeter data, this flight to 387 feet, 4 g's and 98 mph or 143 fps, right below my 150fps target. The H115 although giving almost identical simulation altitude gave 6 g's, 120mpg and 176 fps..which was higher than I liked, nothing bad occured, just had a little roll as it pitched over, but I wouldn't fly it again on this motor or anything harder than the H97, that is a perfect motor for this.

     
    Last edited: Jun 22, 2015

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