Lift off!

The very first Shuttle to enter space was Columbia, launched from Kennedy Space Center on April 12, 1981, one of 132 successful flights. Marred by the Challenger (1986) and Columbia (2003) tragedies, the Space Shuttle program has dominated NASA’s manned operations since the mid ‘70s but is due to end in 2010 and will eventually be replaced by the new Orion spacecraft (expected to be ready by 2014 or thereabouts).


Seeing a Shuttle launch on television is pretty impressive, but to witness that thunderous ascent first-hand must be something else! I hope to make it to Florida before the last flight and do just that, however, in the meantime I decided that my next best option would be to construct a large model version. I visualised this being EDF powered, using Estes rocket motors for visual effect in the climb (just after launch), the model being guided back to land under radio control. External tanks and boosters could be made in Depron with very little additional weight, making it look more like the real thing, although getting all that airborne without an excess of thrust could, I reasoned, be a problem... After a little more thought, I decided to shelve that for a while.


My desire to build a Shuttle wasn’t an overnight whim though. Having followed the progress of space exploration for the last 40 years I’d always intended to build one of the amazing spacecraft that had been developed in that time. I particularly liked the series of ‘lifting bodies’ that were used to explore spacecraft which could return to earth and land on a conventional runway. Interestingly, a publication entitled The Radio Control Manual No.4, of 1972, features an American modeller who’d successfully flown a glow motor-powered ducted fan model of a Martin lifting body research aircraft. By all accounts it had good handling characteristics, including an ability to fly very slowly.

Conceive & Construct
Having gained considerable experience with EDF in recent years I decided to construct a large model of the Space Shuttle from Depron and polystyrene foam, with the intention of producing a lightweight airframe with low wing loading. My first thoughts, and those that I eventually adopted, were to use a 90mm fan with a Mega 22/30/2 motor and 5s Li-Po, the design allowing for the installation of three Estes rockets at a later date.
Built in one-piece, construction of the 47” span Shuttle progressed at a very rapid rate, using Depron glued up with UHU Por. Being very thick at the root, the wing gives considerable stiffness and negates the requirement for additional reinforcement. Meanwhile, the purposeful rocket nozzles were made by moulding glass fibre and epoxy resin around suitable size bottles. Clearly these needed to be relatively fireproof to withstand the heat generated by the Estes rockets.

Now, although my ultimate plan was to fit retracts, I reasoned that it would be a good idea to get the flight testing phase of the project out of the way before fitting them. With the model nearing completion, then, covering the wing l.e., nose and parts of the rear fuselage with nylon cloth and resin, coupled with the addition of a tow hook for initial bungee launches, saw my 5 lb (2.3kg) Shuttle ready for its maiden outing.

Out to Launch
Bungee launching deltas from the ground is quite difficult as the elevons can’t rotate the model whilst the bungee’s under tension. This being the case, I decided to launch my Shuttle from waist height. It immediately flew well, although its 3.5 lb of thrust wasn’t really enough as the climb rate seemed a bit disappointing; a more powerful motor / fan combination was clearly needed. Fortunately, I’d had good success with an Aeronaut turbo 4000, Kontronik 45/9 and 7s Li-Po in my 10 lb Skyhawk, so this combination seemed a good bet. Mind you, in the event I could only obtain a Kontronik 45/10, using 6s Li-Pos, however this combination proved very good and improved the model’s performance immediately.

Actually, the Shuttle proved easy to fly and looked superb in the air. One interesting characteristic is the slow speed performance, indeed it’s possible to raise the nose, throttle back and descend almost vertically in a very controlled manner. By juggling the throttle and raising the nose you can make the model appear to stop dead without losing height. In reality it’s probably moving forwards very slowly, yet in a slight headwind it looks to be stationary. I was pretty impressed overall, in fact the model’s performance gave me enough confidence to go ahead and fit retracts. A double edged sword, for whilst they looked great they almost certainly slowed the rate of climb.
Fan Mail
All was well until the motor shed its magnets after a few flights. I was quite surprised at this, as the Kontronik 45/9 in my Skyhawk is still going strong after three years. Anyway, Kontronik replaced the duff motor without question, and I was back in business.

Now, although the Shuttle was flying really well, I still wanted a better rate of climb and duly swapped the Kontronik motor for a Mega 1200 from Puffin Models, replacing the ESC with a 100A unit. As a consequence the all-up weight increased to 7 lb but the thrust available on 9s is probably giving a 1:1 thrust-to-weight ratio. This combination produces 2100W and provides the best performance, with a very respectable climb rate - not vertical as the drag from the airframe is high, however, the realism is good.
The model would take off from tarmac but, as Shuttle experts will know, the aircraft sits very nose down on its undercarriage and with the rear legs in the scale position the take-off run is very long before the elevons bite sufficiently to raise the nose off the runway. As you’d expect, landings can be extremely slow, and are very easily controlled.

3, 2, 1...
The model creates quite a stir wherever it’s flown and was voted the peoples’ favourite at the Basingstoke Electric Fly-in last September. This event is fantastic and with George Worley at the helm, backed by a  Basingstoke MAC, over 200 models could be seen. With such interest being shown, the time seemed right to install those rockets into the three exhaust nozzles. I’d never tried rocketry before but ploughed ahead thanks to advice from Channel 4 Models of Bournemouth. With this I purchased Estes C6-0 ‘booster’ engines and installed them - friction fit - within a plastic tube firmly fixed inside each nozzle. Ignition was via a servo-operated push switch, the power to ignite the starters (in parallel) coming from a 3s 450mAh Li-Po. Clearly there’s a fire risk and personal safety issue with these rockets, so a hand-launch was clearly out of the question. A toe release system was therefore used, plus the added safety of an isolation switch within the circuit that wasn’t made active until just before release, a live status being indicated by an illuminated LED.
With the Shuttle away I settled her in the circuit and, after few passes, pulled up into a 45° climb, issued a ‘3, 2, 1’ countdown and pressed the ‘ignite’ button. All three rocket cartridges fired at the same instant and produced a good quantity of smoke and flame, after which the cartridges were ejected with simultaneous flashes and pops. I didn’t notice any increase in thrust, but it was a very enjoyable experience for those watching. After the model landed there wasn’t any evidence of heat damage, so it appears that I’ve got the design right in this respect.

Worth It
Getting the Shuttle to where it is today has been pretty costly in terms of financial outlay for fans, motors and Li-Pos, but I’m very pleased with the result. The next step is to install smoke cartridges (from Robotbirds), which will provide smoke for four minutes. I’ll have to check the safety aspect first, though, as I believe they run very hot.
I hope to fly the Shuttle at the main electric flight events again this year, but in the meantime check out ‘model shuttle with firing rockets’ on YouTube as a taster of what you can expect to see. Now, about that external tank and solid boosters...

DATAFILE

Full-size:    

Wingspan:     78ft (23.8m)
Overall length:     Orbiter - 122ft (32.2m); with solid rocket boosters - 184ft (56.1m)
Take-off weight:     2250 tons
Thrust at launch:     3862 tons

Model:    
Wingspan:     47” (1194mm)
Overall length:     65” (1651mm)
Motor:     Mega 1200
Li-Po:     9s 3700mAh
ESC:     Turnigy 100A HV

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