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X-20 DynaSoar/Titan-II model

Built May, 1999

Scale model built for the Future/Fiction (F/F) Sport scale event, flown at the Mick Wilkins Memorial Scale Meet at NSL-99.

This is one of many proposed versions of the X-20 Dyna-Soar, in this case to have been launched atop a Titan-II booster. The outline drawing by Dan Joyce showed an X-20 looking a bit simpler than the later version people are more familiar with. That outline drawing also showed the windscreen, no jettisonable cover was indicated.

The colors and markings were extrapolated from a combination of a crude artists conception but mostly based on the pattern of the Gemini-Titan, with appropriate use of US Air Force insignia and lettering.

Model is scaled at about 1/46 scale, a BT-80 (2.6") diameter body, 32.6" long. To make it fly stably and straight, it used 6 ounces of noseweight to make it balance ahead of the 1st stage/2nd stage interface. See model assembly drawing at bottom. In case of nose up or nose down lift by the X-20, which would have made the model tend to loop, the fins were angled slightly to make the model roll. This was proven out first by building a smaller scale BT-50 boilerplate with a very crude non-gliding X-20, and deriving a worst-case CP using Tom Beach's CP portion of his Rocket Stacks to determine how much noseweight to use. The boilerplate flew straight up, no problem.

X-20 was built out of balsa sheet. The outline was cut for the bottom fuselage out of 1/8" balsa and vertical formers glued into place. Light and easily curled 3/32" balsa was used to make up the fuselage sides and top. The nose section was done in a similar manner, two sets of curved balsa sheeting to match the two different slope angles, as well as a solid tip sanded to shape. Holes in the formers allow for the X-20 to fit atop a BT-20 extending from the Titan adapter section. The X-20 was built for the elevons to pop up for glide, held down flat by the BT-20. For a finish, the X-20 was covered in black Towerkote (goes well around curves) and sprayed clear flat after decaling.

The adapter was built from .02" plastic sheet. Complicated cross-section change from the fuselage of the X-20 to the round body of the Titan. Location of X-20 centerline compared to Titan body also makes the adapter eccentrically off-center. See the drawing at below right. Noseweight added to the BT-20 to extend the noseweight as far forward as possible.

Titan body made from BT-80, actually Totally Tubular's 34" long BT-80. Separation point just ahead of the top black roll pattern. Fins built up from .02" plastic.

Markings - The X-20 US Air Force and USAF white lettering was made by Tango Papa decals. Stars and bars on the wing and Titan taken from old kit decals. US Air Force black lettering and simulated rectangular/semi-oval openings were homemade decals, clear sheet run thru a photocopier. The simulated opening wraparound decal however had some flaws, the toner started to flake off a bit.

Black roll markings were a problem. I normally use Microscale's black solid color sheet, but they no longer make them and this model wasn't important enough to justify using what little I have left. I used some old Sig solid color black decal, but it was fragile and 2/3's of the rectangles cut out cracked or tore. But finally they were done. But after drying they dried with wrinkles in many spots.

The "coup de grace" for a string of finishing problems was in applying the clear flat coat to the Titan. The clear flat I wanted to use (Model Master) happened to attack the aluminum paint used (fortunately I tested it first). And Krylon's clear flat made decals stand out terribly, they made the clear film look a bit frosty. So I used Microscale's clear flat, which comes in bottles and needs to be airbrushed on. Unfortunately I didn't test that (why, I don't know). It seemed to be OK but after awhile some white specks showed up, some of the clear flat had "spit" out and made the specks show up. Tried to clean it off, it's water-based, but it had dried too much to clean off and just smeared. I've never had a model go through so many problems in the painting/finishing phase.

The flight was on an E15-4, launched from a 6' C-rail. I let it fly at a bit of an angle into the wind for concern of how much it would drift downwind, as there were trees about 400 feet downwind. But it weathercocked a pretty good bit too, and it rolled quickly, needed only about half the roll angle in the fins. The weathercocking caused it to be pretty close to the ground at ejection (under 100 feet?), but the recovery system held up OK (twin chutes on the main body and twin chutes on the heavy nose section, each chute with its own 6' long 1/4" elastic shock cord). The X-20 came off, did a couple of stalls, and settled down into a quick glide.

Took second place in team division at the Mick Wilkins meet, beaten by one point! Ahhhhhh!

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NARAM-48 update (2006)

One of the events for NARAM-48 was Future/Fiction Scale. So, the X-20 Titan model from 1999 was upgraded. A new Titan-II body was made, to solve various shortcomings of the orginal, including the finishing problems. Also, the single engine mount for an E15 was changed to two 24mm mounts for a twin D12 cluster. The model was flown for the Southern Neutron Team

The model was in 4th place in static judging, at 685 points. The leading Team Div. model at 730 points was the Bumbling Brothers Team (Bob & Peter Alway), who also had an X-20 but the Titan-III version.

The flying made the difference. The took off nicely, boosted well, ejected near apogee, and had good chute deployment. The X-20 glided great (for an X-20). It scored 200 flght points, to move from 4th to first. Among the mission points it scored were glide, two-engine cluster, and "tracking radar beacon" (Walston tracking transmitter). The Bumbling Bothers Team (Alway Brothers) model did not have a glide capability.


Photo by Greg Warren


Assembly and stability plans for the model.


Outline, colors, and markings interpretation based on an outline drawing by Dan Joyce in the June 1986 issue of American Spacemodeling magazine, as well as Gemini-Titan style of patterns



X-20 Titan-II In Static Judging

Several models during judging

The Alway Brother's model

On the pad, using a C-rail

Tom Beach, Sport Rocketry Editor

Launch on two D12's

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