Vertical Distance on a Single Tank of Gas

[kerbalkicker]

The Challenge:

Build a rocket with a single LFE, a single LFT, and if necessary, a SAS module (I can't remember if I needed one or not - if it's stable without it leave it out). Launch, and try to maximize your final altitude via careful throttle control.

Your final altitude is the point at which your vertical ascent stops. Not when the rocket cuts out.

My record, after 4 trials, is 22,586m straight up. I suspect this can be stretched a bit further, perhaps another 1000m or so.

This goes without saying, but stock parts only.

[millsw]

Hmm...I'll try it. BTW, 2 LFT's and an LFE without a parachute or anything can make orbit

[Oviraptor]

52,369m on first attempt.

52,396m on second.

Edit: I got it up to 52,656m, but only if you allow a single decoupler on the bottom to remove the stickiness.

[kerbalkicker]

52,369m on first attempt.

52,396m on second.

Edit: I got it up to 52,656m, but only if you allow a single decoupler on the bottom to remove the stickiness.

o_0

That's... impressive. And yes, a decoupler to leave the ground is allowed. I forgot about that, but I think I used 1 too.

[Oviraptor]

It's actually not that hard, just leave the thrust in the middle.

[kerbalkicker]

It's actually not that hard, just leave the thrust in the middle.

Is that all you did?!?

More experimentation is in order! FOR SCIENCE

[foamyesque]

Hmm...I'll try it. BTW, 2 LFT's and an LFE without a parachute or anything can make orbit

Really? The lowest I've gotten is 3 tanks.

[kerbalkicker]

52,369m on first attempt.

52,396m on second.

Edit: I got it up to 52,656m, but only if you allow a single decoupler on the bottom to remove the stickiness.

The best I've been able to do on a single LFT is about 30 km. Were you using stock parts?

[andydouble07]

Hm... Some testing must be done

Full throttle all the way, no technique: 29,404 m

Steady 100 m/s until 10km, then full throttle: 42,229 m

I guess it makes a pretty big difference.

[Oviraptor]

The best I've been able to do on a single LFT is about 30 km. Were you using stock parts?

Yes. If I knew how to take a video of it, I would.

[Frederf]

I was thinking about this as challenge. Pod/LFT/LFE is an excellent testbed for liftoff methods. Your peak one-dimensional altitude must involve one technique that is absolutely the best for that purpose. Your only real control is the throttle. The faster the throttle the better Oberth and less gravity drag but more aero drag.

Since I'm a little lazy with the math I'll go for T+U increase from point 0 at launch to point 1 at burnout as the yardstick for success.

U0=0

U1=m1*(GM/(x1+600,000)^2)*x1

T0=0

T1=m1*v1^2 / 2

62.5*200,000 Ns of thrust-time

5,500-3,300 kg weight

dV=A(t)=Thr/m(t)=Thr / 5500-2200t/62.5

=int[0,62.5] 200000 / 5500-2200t/62.5

= -5681.82 log(5500-35.2x) [x=0,62.5]

= 5681.82 log (5500/3300)

= 2902.42

x1 = int(int(A(t)))[0,62.5]

= 5681.82 x - 5681.82 x Log[5500. - 35.2 x] + 887784. Log[-5500. + 35.2 x] (0,62.5)

OK I'm getting tired of the math now. And my A(t) is missing gravity drag not to mention aero drag. I did manage to get 45,343m or something with the keep it at 100m/s until 20km though. Much better than my constant throttle 23/24km runs.

Getting the general equation for optimized launches (at least in one dimension to start) would be a great accomplishment.

[kerbalkicker]

Getting the general equation for optimized launches (at least in one dimension to start) would be a great accomplishment.

Heh, see this thread: http://kerbalspaceprogram.com/forum/index.php?topic=2230.0

Also, you guys are starting to make me feel REALLY inadequate with the altitudes you're achieving.

Full throttle all the way, no technique: 29,404 m

The best I did with it pegged at WOT is 20,873m. WTF.

EDIT: Wait, are you using a SAS unit or not?

[Oviraptor]

No SAS, that'll just slow you down. A small rocket like that is easy enough to control without one.

[kerbalkicker]

Aahh ok, that makes sense. I used one because I'd rather just let it run unattended than spend the whole flight trying to keep it pointed where I want it.

[Xenoc]

42,935: Full throttle until 100 m/s then down to keep the speed at that level. Full burn after 10km.

50,717: Throttle to 100 m/s, maintain that until 4 km, then maintain at 30% throttle until 15 km, 60% throttle til burnout

45,600: 75 m/s until 4km, 30% until 10 km, 50% until 15km, 100% til burnout.

48,384: 150 m/s until 10km, then just maintain the throttle at at that final level until burn.

51,460: 150 m/s until 10km then gradually ramped up to 60% thrust by 20km

Tried a few variations with low burn rates at the top to try and keep thrust going until out of the atmosphere, but it never gives you a high enough final velocity to pop you up to a a good altitude. 60% thrust early on to get you up and travelling, then reduce thrust until you're in thinner atmosphere appears to be the best way forward. Keep your velocity below 150 m/s in the lower atmosphere. You need to be doing in excess of 600 m/s at 30km to stand a chance of getting over 50km.

These were all without 1st stage decouplers.

EDIT: 53,401 by getting to 100 m/s for the first 4km, then staying at 30% thrust until 10km, then gradually ramping up to 60% before burnout. Not sure there's much more can be squeezed out.

[koberko]

Here is mine attempt; 68 823 on single tank.

I used one LFT and one LFE, and one decupler to remove 'sticky' take off effect.

I have take off with 40% of power, and when I reached 100m/s, I reduce power a bit, then I reduce it for each 30 m/s I gained till I reached 200 m/s. Then I went full power till I reached some 900 m/s. Then I left it to slow down slowly till top height.

[koberko]

Second attempt; 89 919m

I have lift of at default thrust value, and when I reached 200 m/s, I started full burn witch lasted till 1050 m/s and some 25 000m height...

[icefire]

http://i.imgur.com/4PXI3.png

Ended up landing in the desert north of the launchpad.

There were no survivors.

[icefire]

Second attempt, 90,249

[Xenoc]

Second attempt; 89 919m

I have lift of at default thrust value, and when I reached 200 m/s, I started full burn witch lasted till 1050 m/s and some 25 000m height...

Yeah, the new atmospheric model in the September release changes this challenge quite substantially. Using that method int he old version only got you to 700 ish m/s at 21,000m and 41,200 m max altitude.

[RangerDanger75]

Hmm...I\'ll try it. BTW, 2 LFT\'s and an LFE without a parachute or anything can make orbit

I feel like you\'re trolling me, the best i got was 1330 m/s at 36km. I was throttled way back through most of the atmosphere. I kept my velocity at 100m/s under 15km and then I left the throttle right at the line below the 'E' in the word throttle on the gauge.

[imsabbel]

No, he is not.

Although it is possible that it does not work anymore in 0.10, due to the change in athmospheric model.

A plain stack: Module - tank - tank - engine made it into orbit easily enough to even allow a reentry burn.

Maybe your 100m/s below 15k is a bit too conservative in this case, as you will get TONS of gravimetric losses.

[koberko]

Here is my current best; 92 824m

I have started with default thrust, and when I reached 15 000m i initialized full burn.

[Rickenbacker]

Steady 100m/s all the way got me 27,900m... Not the best method, then.

Half throttle all the way, 32,300m - with a decoupler for the capsule, forgot it the first time and wanted to get my Kerbonauts back!

Half power to 10,000, then full throttle, got me 33,200 - best so far!

[Jarnis]

Here is my current best; 92 824m

I have started with default thrust, and when I reached 15 000m i initialized full burn.

Nice try, but not nice enough.

Through careful throttle control, the new record stands at... 95 011m

You may now continue your throttle optimization training, cadet. 8)