Glider on top of the booster (i.e., X-20 Dyna-Soar)

The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.


Aug 13, 2009
Reaction score
Hi there,

I am considering a design which is inspired by the X-20 Dyna-Soar or some of the early Space Shuttle designs, such as the 1971 MSC-027 concept (I can highly recommend Dennis Jenkin's Space Shuttle book for inspiration).
I'd love to do a semi-scale version, but for the time being I don't want to be constrained by scale-considerations for the booster or the glider.

Obviously a glider on top shifts the CoP forward quite a bit, but my quick'n'dirty RockSim design is "GO" as far as stability is concerned.

I plan to work start the whole thing from the top and then proceed towards the bottom: I'd like to use a BT-20 tube with a balsa nose cone on it and and try out different delta wing shapes and stabilizers on the wing tips or a single one in the middle. Then I'll figure out a good way of holding the elevators back during ascent, before designing a booster that has fins large enough to counter the small glider on top of the whole rocket.

Has anybody tried a design like this? Any hints or anything?

Thanks a lot,

Last edited:
I did a few years ago. You can find the details here:

It is a approx 1/72 semi scale X-20 and a BT-60 body.

I used paper label elevators on the orbiter instead of the elastic/harness method, and it worked well. Mostly.

I did not add any nose weight to mine, I wanted it to detach and glide. It does glide but it won't win an contests.

I used 4 fins. 2 over sized lined up with the wings of the X-20, and 2 normal sized. The 2 normal fins have about 2 deg of angle to induce spin for stability.

It is stable under boost and most of the coast phase, as it slows down it starts a fun squiggle where it starts to oscillate.

Have fun and post photos!
Also from the archives is this version of the Dyna Soar with a gliding booster.

We handled the stability issue by making an extension from the transition that went up inside the hollow body of the glider. This tube held some noseweight in order to counteract the span of the glider. Becasue it was attached to the main rocket and not the glider it didn't affect the glide at all.

Way back when, the gurus at Centuri put an X-24 Bug on top of the booster section of a Saturn V model. You can read about it in one of the Centuri newsletters in Jimz archive - I don't remember which one but download 'em all - they are all great reading!
I flew an X-20/Titan II at NARAM-51. I put 2oz. of nose weight in the transition so that the CG (loaded with two B6-2's) was at the prototypical stage separation point (mine was single staged.) I'd seen this marked as the minimum CG for stable operation on someone else's model. Here's a picture taken by Chris Taylor in flight.

DynaSoar in flight.jpg
Roachwerks now offers a DynaSoar kit (capsule and transition section) -- I bought one at NAHRAM51 to evaluate. I have also collected papermodels as alternatives -- planning stiffening as many people discussed in other forums. Since it never actually flew on anything, Titans or a Saturn I are launch vehicle options -- I'm trying for a finless Titan configuration. The Meatball group's idea for the weight bearing tube into the capsule was the inspiration for how to approach the CG. Probably end up on clear fins but wouldn't 2 engine cluster, staged, finless be a wonderful dream? (I have GOT to quit sniffing those engines!! -- grin) I have to figure paper models will last as well as a Dr.Z shuttle -- and easy to replace. Maybe keep wood version for static display?
I built a BT-80 based model, at about 1/46 scale, in 1999. Based on the Titan-II and an early concept for the X-20.

A huge problem with a model like this is all that wing area up front that wants to act like a canard. Not just to possibly make it plain unstable but if it is misaligned by say 1/2 degree, it could pitch into a loop like a rocket glider with too much up elevator trim.

I worked out what I felt to be a worst-case calculated CP, and chose a very healthy stability margin. I first built a small boilerplate based on BT-50, to confirm the stability. It flew great, very stable (did not try to make the X-20 glide, the boilerplate was only to test stability.

The glider was built-up, at least the fuselage. The fuselage bottom from light 1/8” balsa, the sides and front mostly from 1/32” balsa over formers. The formers/bulkheads has holes thru them a bit larger in diameter than a BT-20, so that the X-20 could slide off of a BT-20. The elevons were hinged in a way to come up to a certain angle for glide. And to be set flat for boost.

The Top of the Titan second stage had a length of BT-20 sticking out of the top of it. The BT-20 serves two purposes. One was to hold the X-20, very simply, so it would sit there for the ride up on boost, and slide off and away when the chutes deployed to make the second stage point nose down. The other purpose of the BT-20 was to house a LOT of noseweight inside of it, so that the most effective use was made of noseweight (lead and resin), otherwise there would have needed to be more noseweight inside the second stage if it was not mounted more forward inside the BT-20 extension.

One last thing the BT-20 served to do was for a lever arm on the X-20 elevons to be pressed by the BT-20, to hold the elevons flat for boost. The lever arm was 3/64" brass, so I could bend just the right amount of adjustment to make the elevons perfectly flat for boost.

The Titan-II’s fin were built-up from .002” thick plastic. This was to make them lightweight, because every gram added to the fins at the back would require yet another gram (actually a bit more than a gram) of noseweight up front to balance out at the desired CG.

For NARAM-48, I had to build a new the Titan-II main body, and changed the power from one E15 to two D12’s. I arranged the D12 engine mounts to be skewed a little bit to help to make it roll some on boost, so that if there was any tendency to pitch nose-up or nose down from the X-20, it would help to even that out. For the original Titan-II body, with an E15, I had rigged the fins to be canted about 2 degrees off, all in the same direction, to make it roll slowly aerodynamically. But that was not very obvious from just looking at it. On the new body I do not recall if I did the same or made them straight and just counted on the skewed D12 thrustlines to make it roll some.

It won at NARAM-48, coming from behind (3rd or 4th) in static, due to mission points. Same thing 2 weeks ago at NARAM-51 tied for 3rd in static, moved to 1st from the Mission Score. But it was harder, because the first flight only one D12 lit, and I was lucky it was not destroyed. Some damage to the Titan-II, which took about 10 minutes to fix. Then the second flight ignited both D12’s and it flew great, and the X-20 glided about the best it ever has.

Below, a drawing showing the model layout. Three pics by Chris Taylor from the NARAMlive site, and one pic I took that also shows the “Bumbling Brothers” team’s (Peter & Bob Alway) Titan-III based X-20 model in the background.

- George Gassaway





Last edited:
Here are a few more photos of George's Titan. This was of his first flight when only one motor lit.



Then, a beautiful second flight.

I missed glider separation. But it did, and had a great great looking glide back down.





Last edited:
Wow, those are all great [pics. Since I was taking a liftoff shot of the first flight, close-by and on one knee, I did not even see what happened after liftoff till it was on the ground. So I had wondered when (how high up) it ejected, and was SO glad the X-20 got off before it hit or otherwise all that noseweight in the BT-20 mounted inside the second stage would have smashed it. That ejection is higher up than I than I thought but of course the X-20 was not off yet, either, wow that was close. Also interesting to see from the photo sequence that yes, indeed, it did roll on just that one engine, due to the thrustlines being twisted for roll. Without the roll it would have pitched tighter and faster and perhaps ejected too late, smashing the X-20, and I am not sure it could have been rebuilt on the field to do a flight two, never mind glide.

Also, great to see the pics of the second flight. The chute deploy sequence does confirm to me something I did in prepping the chutes, trying to make sure one of the second stage chutes helped pull out one of the first stage chutes, that I wondered if they might tangle. They did not tangle, but that shot shows how close it was to those two tangling.

- George Gassaway
Someone else had a pretty cool Titan III arrangement of the Dynasoar. This one didn't get any mission points for a gliding X-20, but earned some points for a great looking clustered boost.





That was the “Bumbling Brothers Team”. Peter Alway and Bob Alway.

- George Gassaway

Thanks. I wasn't paying attention. I thought Peter was only involved with judging.

At any rate, I was glad to see your gliding X-20 finally work. I've always thought, if I were to ever build a Titan/X-20, I would want the winged contraption at the top to glide back down. Figures you'd be the one to find a way. I didn't see the appeal of flying it any other way, although Bob and Pete's model sure do make a convincing argument.
Someone else had a pretty cool Titan III arrangement of the Dynasoar. This one didn't get any mission points for a gliding X-20, but earned some points for a great looking clustered boost.

Thanks for posting that set of photos. I hadn't seen them before. That was one nerve-wracking cluster launch!