Looong version:
In 2010, got ahold of a prototype 1/72nd scale North Coast Rocketry shuttle stack kit. Acquired through ebay auction that George Gassoway setup, to help fund a smaller shuttle stack kit George wanted to release.
In 2016, structurally built it to point of naked display.
In 2022, detailed, painted, decaled it based on STS-5 mission.
In 2024, launched it.
Unsure which parts are prototype, and which parts were of the actual released kit. Presume orbiter vaccum formed pieces match the released kit.
Used actual release instructions, even though prototype parts.
Plan was to build, launch once, and then retire. Plan was to not detach orbiter during launch, to reduce risk of damage to orbiter. (Replacement kit is not available.)
Non-exhaustive list of build modifications:
- Swapped some orbiter parts for plastic model parts, as orbiter weight was no longer an issue, given my plan not to detach the orbiter during launch.
- Prototype kit came with both vacuum-formed and foam SRB nose cones, and i used the vacuum-formed SRB nosecones.
- Fiberglassed internals of vacuum-formed SRB nosecones, to make more durable.
- Believe added more balsa to tail of orbiter to make more durable.
- Fairly certain i added some other balsa at various places, to reinforce orbiter.
- Replaced provided SRB paper strips with Evergreen polystyrene strips.
- Replaced provided decals with decals created using Inkscape modified paper model available from https://axmpaperspacescalemodels.com, and then printed with laser printer. Spent good amount of time verifying paper model against reference images of STS-5 (don't recall how many inaccuracies there were).
- Ended up with 1oz extra lead/epoxy ballast in the orbiter nose.
- Other modifications, that do not come to mind
Screw-ups:
- Lower orbiter vacuum-formed scale attachment detail was placed in incorrect position
- Applied some paint/decal details which were not applicable to the model of STS-5 mission.
Launch prep
- Zip tied the orbiter to two of the three orbiter-fueltank attachment points. Zip tie placement was kinda precarious, allowing the possibility for the zip tie to possibly slide free from attachment point (hard to explain without picture. i don't have picture).
- Used Aerotech H128 white lightning reload with delay drilled down to 5 seconds. Rocksimed with representative model rocket to maybe 800' at apogee.
- Setup 6' tall, 3/8" diameter rod.
- Slid stack onto 6' rod, where about 4' of rod was available to bottom launch lug. With a different pad, i might have gotten 5' of usuable rod.
- Inserted igniter into motor.
- Attached alligator clips to igniter leads
- Stuck a dowel into ground right below engine
- Wrapped/zip-tied alligator clip wires to dowel below motor, to minimize amount the clips could possibly be spit towards SRB fin cans.
- Juiced the igniter.
- Stack ripped off the 4' of usable 3/8" rod just fine.
- Stack flew in direction of lean of the rod, which was perpendicular to 5mph wind.
- Maybe 300-500' up, the right SRB (and associated fin can) seperated from the rest of the stack.
- That caused the remainder of the stack to sonic-the-hedge-hog-spin around vertical-center of the fuel tank, for a couple seconds
- Then ejection charge blew
- At ejection the orbiter performed unplanned detachment
- Orbiter came in ballistic
- Remainder of the stack came in under chute, just fine.
On the ground, we found one SRB with charred fin can. The fins had broke away from the fin can cylinder on impact. This was the SRB that detached in flight. Nose cone of this SRB impacted sorta hard into mud, but did not break. The internal fiberglass reinforcement was a wise idea.
At orbiter impact site, 5" of the nose were broken into 10 pieces or so, and embedded into a couple inches of mud, and below that hard dirt. Orbiter damage stopped where the front end of balsa "I-beam" begins. One of the orbiter-fueltank attachment points had the fuel tank portion of the attachment point zipped tied to it (the fuel tank half of the attachment point got unexpectly ripped off from fuel tank). Both wing flaps broke from from orbiter, as their RC airplane hinges broke.
At the remainder-of-stack landing site, everything was pretty intact, other then SRB dowels popped/broke free during impact, detaching the SRB. Fin can of this SRB was not charred.
Based on photos taken with stack sitting on pad, i can see that one of two zip ties was not adequately holding its attachment point parts together
Based on burst mode pictures, i can see that the topmost of two dowel connection points for the rightmost SRB broke, while the stack was still on the rod. After about 1 foot of travel.
- This caused the right most SRB to not be parallel to the rest of the stack.
- This caused the right most SRB fin can to end up in the plume of the H128 motor, explaining why that SRB fin can was charred, while the other SRB fin can was not charred.
- At about 300-500' up, there was enough sustained drag from SRB and associated fin can, that the entire SRB (along with associated fin can) ripped completely free, introducing the sonic-the-hedge-hog-spinning of remainder of the stack.
- All that violent spinning and then ejection charge, ripped one orbiter-fueltank attachment point from the fuel tank, and then allowed the other inadequately zip-tied attachment point to completely fail as well, letting the unbalanced orbiter to free itself from rest of stack.
- Orbiter came in ballistic, as orbiter was never balanced for glide (plus orbiter had extra nose weight).
Don't believe the igniter clips could have been spit far enough towards right SRB fin to get above SRB fin and cause drag. Seems like the topmost (prototype) dowel was just not robust enough to handle the initial thrust of the H128W motor.
If i had it to do over again, i'd:
- use more robust dowels
- add a third dowel nearer the top of the SRBs
- place some thicker material (e.g. balsa/basswood) on inside of SRB tube and fuel tank tube, at place where dowels are glued, as an extra precaution
