Tiny Shuttle Challenge

[Guest]

It is hard to get it much lower than the 1,560 kg one. I almost got a 1,360 kg one to orbit, it's short a few tens of m/s -- an absolutely perfect launch could probably do it, but it would take a lot of finesse: too high isn't efficient enough, lower gets so hot it burns the wings off. I'm starting to think the superlight < 1 ton ones are non-starters, they should work in theory but in practice they're hundreds of m/s short -- I suspect they produce so much drag in the lower atmosphere that it more than negates the efficiency gain from the lighter engines. Also Spiders have really bad Isp. 

If you can get your 1.32 ton version to do a round trip, I doubt I'll be able to beat that. 

[sevenperforce]

7 hours ago, Brikoleur said:

If you can get your 1.32 ton version to do a round trip, I doubt I'll be able to beat that. 

It makes orbit with some fairly straightforward flying… Not really too much work. I have about 40 or 50 m/s of margin after deorbit. However, I keep having trouble with entry. That single fin really, really wants to burn up.That single fin really, really wants to burn up.

[Guest]

BTW I made an SSTO based on this design, and it weighs in at 1,184 kg on launch. Since it has a quite a bit less dry mass I think it's close to the lower limit of what can be achieved with this challenge. I also tried stacking the stages in a conventional way (which would disqualify it for this challenge), and wasn't able to get much lower. If I try to get cute with Ants and such, drag becomes a real problem which eats away most of the fuel I save from the lower dry weight... 

The closest I've gotten to a material improvement on my current submission is 1360 kg. I have failed to make orbit with it, but only by a few tens of m/s -- a better/more patient pilot than I could probably do it. For my piloting skills though I think 1,560 kg is where it's at -- it makes orbit easily, deorbits easily, and lands easily; any further optimisations I can make, make one or more stages of the journey so much harder that my piloting skills aren't up to the challenge.

[sturmhauke]

I was experimenting with using Junos for low altitude boosters, not sure if that will break any records though. I managed to get a 1530 kg shuttle (start mass) up to about 45 km altitude and 900 m/s. I had 2 Ants on the orbiter and 2 Junos on the boosters.

[Guest]

9 hours ago, sturmhauke said:

I was experimenting with using Junos for low altitude boosters, not sure if that will break any records though. I managed to get a 1530 kg shuttle (start mass) up to about 45 km altitude and 900 m/s. I had 2 Ants on the orbiter and 2 Junos on the boosters.

Hey, great minds and all that. Got a ca 1400 kg one to orbit... minus the wings, which burned off. The ascent profile is tricky. It’s doable with sufficient finesse I’m sure.

[Aetharan]

I'm tempted to see if I can make this basic design work on the side of a rocket instead of on top of it.  https://imgur.com/a/ZZiBh5x

Relies on the kerbal's chute for aerodynamics, but it did re-enter safely and make a horizontal landing on the runway.  Sadly, its position on top of the first half of the launch system disqualifies it as-is.

[Guest]

I made a borderline cheaty innovation that cut a tiny bit of dry mass and may have improved aerodynamics, which let me remove another Oscar, which led to better balance, which led to higher TWR, which led to more efficiency, so I got the same orbiter as before to 90 km orbit with a starting mass of 1322 kg and over 150 m/s left over.

Botched the reentry corridor, landing in the desert, and then touched down too hard so I lost the nose cone. That was a pilot brainfart though. This one will work.

Edit: Here's a qualifying attempt. I still muffed re-entry and fell just a bit short of the runway, but this time I brought everything down intact so it qualifies, since a runway landing wasn't a requirement.

• The ascent profile has to be pretty steep, otherwise drag losses will get too big. This wasn't my most optimal launch so far, I had a better one that had an even taller arc (the one I reference above).
• I've tried to optimise this even further, e.g. by swapping out the battery for the smaller one, but that messes up the aerodynamics and despite the lower dry weight it didn't make orbit. I also tried swapping out the landing skid for a pair of grip pads, but I wasn't able to bring it down in one piece. 
• The use of the Decoupler-06 this way is borderline cheaty but, hey, in love, war, and KSP challenges anything goes, no?

If someone can further improve on this, I'll be quite impressed because I don't think I can!

 

Edited August 22, 2020 by Guest