My Upscale Orbital Transport

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Well-Known Member
Jun 2, 2011
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I thought I'd start a thread to track (oh ok ask advice!) my latest project.

Having flown a clone of the original Estes Orbital Transport I'd like to build an upscale. I can't decide what scale would be best, either BT-60 or BT-70.

If I went with BT-60, it could *probably* fly on an Estes D or cluster of 3 x Cs. I'd have to see about the final weight.

The other option is BT-70 which results a model quite a bit larger. This would *probably* be able to go on 2 x D12 but I'm not sure, what do you guys think?

Both of those options wouldn't get much height but thats not really what I'm looking for. I feel a bit daunted by the BT-70 as it would be a pretty large model.

I'm thinking of using 1/8" Liteply for the fins and they'd have to go TTW to be strong enough. Sound about right?

I can only help if you want to go up or down by 3X, BT-80 or 7.1mm micro-maxx.
3X Upscale fly's wonderfully on 4 D12 -3's or old estes E15-4's The biggest problem is turning the nose cone. very thing else is really a piece of cake.
Woah, the BT-80 version is huge!

I'd like to do the BT-70 version as it's a bit larger the BT-60 version. I thinking 2 Ds in a BT-70 one would be pushing it, three would be better but that makes TTW much harder.
Mike -

I built a BT-60 based Orbital Transport, it flys great on D12-5's. I have not yet flown it with an E, although the MMT is made to handle the longer E9's.

My O.T. was built with 1/8" balsa. I sandwiched the canard wing with 1/64" ply sheet for durability. For the main body, I used tubes and the nose cone from a Mean Machine kit, and BT-20 for the under-wing scramjet motors. The glider tube was hand-made, by rolling printer paper around a 29mm MMT tube covered in waxpaper, and brushing on thin epoxy. I haven't finished the glider yet, but instead for the piggybacker I have been using a styrofoam Guillow's space shuttle glider which is approximately the right size.

There's a photo and a video on my homepage (URL in my siggy). The glider didn't detach on this flight, adding more nose weight to the booster fixed the problem (by preventing the "flat stall" effect seen in the video).
A BT-60 sized OT is about just right for a single "D12" engine.

Mine is just a tiny bit under one Meter (39 inches) long.

A BT-70 version would be a little more than 2X and a single "D12" wouldn't handle it

I'd go for the BT70 version. :D

A 3 x D cluster would probably lift it fine. If you didn't make the main wings (canards) too heavy, you would probably be ok without TTW mounting. I'd go with 1/8 basswood (rather than ply, because basswood is nice and strong and a *lot* lighter) and surface mount. Use the "rivet" method when attaching the root edge, and then good solid filets. I *highly* reccomend Fix-It epoxy clay for these kind of fillets (available from Apogee.) I've found that the body tube will fail before the attachment joint when done like this. If you get the 1/8 ply 3 x 24mm BT70 centering rings from BMS (now a stock item) and put an extra one or two up along your stuffer tubes between the leading edge of the canard wing (where it meets the airframe) and the aft end of the rocket, then epoxy the mount in place, you'll get suprising rigidity of both the airframe and your wings if done like I've described.

Good luck! Sounds like a fun project.
I;ve only done one size up-scale of the OT and it was BT-70 based. I've done several variations of it...

single 29mm
dual 24mm
24mm with dual 18mm

All flew just great. Very stable, good altitude, perfect deployment of the chute (36" military flare chute) and the glider too.

Photo's of various versions can be found on my personal web site at:

go for it! my best paint scheme matched the original kit, but included custom blackened areas on the underside of the orbiter to match what *should* be heat shield tiles.

great stuff :)
a 3 D12 Cluster will fit perfectly in a BT-70

Just so you know the BT-80 OT does not use TTW fin mounts. epoxy rivits only, and has survived 3 no deploy Core samples;)
losing only the forward 14" "crumple zone" built into the design. The reason for the coresamples???... a clogged ejecton baffle WHO KNEW!! If you use a baffel make sure you can reach it to clean it out:(

Those 4 D12 Do make for a pretty flight
Originally posted by Micromister
a 3 D12 Cluster will fit perfectly in a BT-70

Actually, three BT50's (24mm mount tubes) inserted in a BT70 leaves a *slight* gap all the way around. You could fill this gap by *heavily* laying on the epoxy prior to inserting the tubes (possibly.) Or, as I did in my BT70 Atlantis, you could use 3x24mm cluster centering rings for the BT70 from BMS. They fit really nice and ensure that your cluster is perfectly centered in the airframe.
You could also use either of two cluster kits from FlisKits:

EMK3-24-70: Three 24mm mounts to fit in a BT-70. This kit uses a BT-69 tube that slides into the BT-70 (great for making interchangable motor mounts) and includes motor hooks

EMK3-24-70R: Three 24mm mounts to fit in a BT-70. This kit uses a pair of centering rings to fit in the BT-70 and does NOT include motor hooks.

Both are 4.0" long and can be built to take Estes E motors.

I've built an upscale Orbital Transport in BT-60 with a BT-55 glider and BT-50 "scramjet" engine tubes. Mean Machine nosecone for the core, and a hand-turned balsa cone for the glider. I took some real effort to keep the glider weight down, with only minimally sealed balsa on the fins, and red (K-mart stuff that I think is "fresh look" now) and silver (tstors)paints chosen for good coverage with minimum-weight, thin coats. I scaled up the patterns by 1.75%, though I may have had to improvise a little on the sizes to get the BT-50 scramjet tubes to fit right. I built it at least 13 years ago, so I'm not entirely clear on all the details anymore.

The model flies great on a D12-5. I don't fly it much, as it's a bit bulky to transport, but it's a blast to fly. It's no big stress to fly because I don't have to worry about clustering, but it's got plenty of smoke and fire for me.

You can find a picture that Vern Estes took of me holding it about 3/4 of the way down this page:
Hi, Peter!

Welcome to the forum!

Haven't seen you since....last night!:D