First (And only) Flight of STS-JATO Prototype 1

[POTKC]

The STS-JATO

The TST-JATO is a modified Space Transport System, which launches from a runway. During ascent the STS-JATO uses it's 3 SSMEs to bring the apoapsis to 100-150 kilometers. The fuel for the SSMEs is contained in a fuel tank, attached to the inside of the cargo bay. Due to this arrangement, however, the STS-JATO is unable to carry any significant payload to orbit, and can therefore only serve as a crew carrier and station resupply craft. It can also recover large payloads from orbit, and bring them back to Kerbin.

Once the shuttle exits the atmosphere, the cargo bay door are opened and the fuel tank is jettisoned. The STS-JATO then uses RCS to move away from the tank. At the apoapsis, the OMS is used to circularize the orbit. The shuttle can the proceed to fulfill its mission target.

Maiden Flight

The takeoff was flawless, with V1 (Maximum abort speed) at 70m/s and VR (Liftoff speed) at 50m/s. STS-JATO P1 lifted off well short of the runway end, and pitched up to 20 degrees to start the climb.

Within 5 minutes the apoapsis was at 100,650 meters. The SSMEs were shut down, and upon exiting the atmosphere the fuel tank was jettisoned.

The OMS was ignited at apoapsis, and the orbit circularized. Due to pilot error, the STS-JATO ended up in a 96X88 kilometer orbit.

After OMS shutdown, the cargo bay doors were re-opened and the docking port extended to test all hydraulics and electrical systems. Several orbital maneuvering tests were also conducted. Kerbal Space Program officials dismiss the proposition that all of this was done just for the "...nice cinematic photos."

During re-entry the shuttle flew perfectly, up untill the moment that aerodynamic heating began. At this point STS-JATO P1 began rolling to the left, and when Mission Commander Jebediah Kerman tried to bring the ship under control it "...began dancing and going in every possible direction BUT where I was trying to point the [CENSORED] shuttle [CENSORED]!!!", as said by the Mission Commander himself. As the heating subsided, the shuttle rolled over and nosedived towards the ground. Jebediah Kerman nearly managed to pull it out of the dive, but STS-JATO P1 impacted the ground at high speed. The impact destroyed most of the shuttle. Below is the preliminary evidence infographic, from the KASAIB (Kerbal Air and Space Accident Investigation Board).

Edited July 1, 2013 by POTKC

[POTKC]

Why have 73 people looked at this, but no-one is replying?

[stupid_chris]

I've seen you send this type of line quite a few times now, so I'm gonna give you a short explanation why.

Sometimes, people just don't have anything interesting to say. Nothing forces us to give you some feedback, and if I don't have anything to say, I won't force myself to spawn a reply just because I viewed your thread.

Having a comment like that even makes people less likely to want to reply. Be patient and learn to accept that sometimes, you just won't get feedback.

[Geschosskopf]

Why have 73 people looked at this, but no-one is replying?

Well, in my own case, you live 1/2 way around the world east of me so I was asleep until just now .

Anyway, shame about the crash. What do you think caused it? Question: Do you use FAR or the stock atmosphere?

My prime suspect is that removal of the fuel and tank mass upset the aerodynamic forces. I'm sure you positioned the fuel tank very carefully to minimize the change in center of mass. However, that's not the only thing you have to worry about. There's also the change in wing loading, which decreases as you burn fuel (reducing mass) while the wing area remains constant. The lower the wing loading, the lower the maximum stable speed of the aircraft. This is because stable flight requires a balance between weight pulling down and lift pushing up. Lift is a function of wing area and speed, so above a certain speed, the lift totally overpowers the mass and the aircraft is impossible to fly.

Thus, my theory is that during your reentry, you came out of the fire into the thick air still moving at very high speed. Suddenly, you had a huge amount of lift but not enough mass to hold it in check, so the aircraft tumbled. But as it fell lower, the thick air slowed it down more and more, decreasing the lift until you ALMOST had a balance again.

If this is true (which I can't guarantee but strongly suspect), then you have 2 options. Either add mass to the aircraft or decrease its wing area. I believe the latter is probably the easiest to do without a complete rebuild. Of course, either option will increase the takeoff run, reduce the effective lift during ascent when mass is greatest, and result in higher landing speed. But I really do think you need to do one or the other.

[Geschosskopf]

Another possible option: Hacksaw variable geometry wings .

Figure out the loaded wing loading in the current configuration. This wing loading is stable so then determine the empty mass and reduce the wing area until the empty wing loading is about the same as when loaded. To reduce the wing area, build the wings out of separate parts instead of single pieces like you have now. Then mount the wingtips on decouplers so you can dump them along with the fuel tank before you de-orbit. I've never tried this myself; this idea just popped into my head.

[POTKC]

I don't have FAR, although I might try to install it and see what happens. It might have been pilot error, I know that planes in KSP can be very twitchy at high speeds, so maybe I should have left the avionics on instead of trying to fly the reentry like on a real shuttle (High pitch-up angle, left roll, then left roll reversal etc.) I'll fly the mission again, and try it with FAR this time.

[andrew123]

Be prepared to put the center of lift right at the center of mass... .

I learned the hard way with FAR... .

[Geschosskopf]

FAR has MANY effects. Besides what it does to airplanes, it has a HUGE impact on rockets. OT1H, it lets you get to LKO with only a bit over 3000 dV, provided you tweak the ascent profile for most efficiency. HOWEVER, it requires long, tall rockets with lots of tail feathers, and their tallness quickly runs you into the ceiling of the VAB, which limits the size of your payloads. And lumpy payloads have to have fairings. Plus, the length of the rockets requires a LOT of RCS to maneuver them, especially once above the atmosphere where the tail feathers quit working. Besides this, I'm sure the web sites like the aerobraking and parachute calculators assume you've got the stock atmosphere, so you probably can't rely on these aids.

So all in all, FAR is a major commitment. Only do it if you're willing to have a lot of side effects you're probably not expecting. But OTOH, probably someday an update will incorporate something similar to FAR, so might as well start getting used to it now.

[POTKC]

I tried with FAR, and the shuttle just started spinning and tore itself apart. I think that as there is no FAR version of the .cfg files for the Tiberdine Shuttle mod, it won't work. So I deleted FAR, and am in the middle of a flight with the second prototype. I will quick save in orbit, and then try to land it without crashing. MISSION UPDATES INCOMING!!!