Challenge: Shortest time to escape velocity

[arachnid]

Jebediah's in a spot of trouble, and he needs to get out of town fast. If he's not on the planet, he can't be prosecuted, right? Help him out by getting him to escape velocity as fast as possible.

Goal: Reach escape velocity in the least time since launch. A table of escape velocities is here. You may use anything from the basic parts or Sunday Punch's parts pack. You don't need to pack a parachute - nobody's going to be returning from this trip.

About the atmosphere: Escape velocity is kind of meaningless at surface level, since the atmosphere is going to slow you down anyway. In order to keep in the spirit of the challenge, if you exceed escape velocity below 70k, the timer stops when you turn the engines off - if you have enough momentum to actually escape. So, for instance, if your last stage burns out at 50k, you may stop counting then as long as you're still over escape velocity when you get to 70k.

I figure this ought to be an interesting challenge in part because of the air-resistance factor - the best approach might not be to peg the throttle the whole way, but to save precious fuel until higher up. Only time will tell.

[arachnid]

Best so far: 2m57s. I'm sure someone can do much better.

Edit: 2m21s, using a two-stage all liquid design.

[Tiberion]

I hit the screenshot key a second too early, so lets say 2m15s

6 seconds later I was already at 3300m/s @ 160k, so we had some vigorous acceleration going on.

7x K2-X engines with a 5000unit tank, with 8 boosters to get you moving.

[Jarnis]

Jeb has left the building (and the planet) in 1 minute 57 seconds 1 minute 53 seconds

'2.5 stage' design with 8x Sunday Punch solids helping up a 8x M-50 Liquids for the first ten kilometers (5200 total thurst in a stable config without bucketloads of SAS modules on ignition - Jeb was in a hurry)

Note that the core fuel tank has no engines on it - it feeds the 8x engines trough the decouplers attached radially to avoid overheating and stability issues. After the main stage is dumped, a very small upper stage (1x M-50) takes care of the final dash for 'the border' (almost blowing up in the process, but hey, when you are in a hurry, you are in a hurry...)

Edit: slightly better run with same config but slightly different thrust usage. Shot taken at 127km going past 3131m/s (escape velocity at 120km). Final velocity at burnout was ~3900m/s. Definitely no need for a parachute...

[Jarnis]

The fact that my first design burned all the way to 3900m/s made me take a look at the upper stage. I swapped the tank to a default liquid tank to save weight and minimize excess fuel but that couldn't quite do it, burning out about 80m/s short of escape velocity.

So, again, the inner Jeb led me to take excess weight off the upper stage. Who needs a SAS module anyway? Jeb sure doesn't...

Same design, SAS module tossed off to the VAB floor, smaller upper stage tank. Quite stable, just some very slight rolling. Burns out just perfectly slightly above escape velocity, reaching the key speed...

1 minute 38 seconds after ignition

(screenie is ever so slightly past the required speed but I'm sure I was under it a second earlier, so... Escape velocity at 100km is 3175.81m/s)

Enough escapes for the night. Awaiting your contraptions that beat this... 8)

[Tiberion]

No success beating that yet, but I did make a study model of yours to see if I could improve it.

I used smaller tanks on the 1st stage, but forgot to use struts on those.

And then I added more boosters.

The result is... fantastic.. for about 40 seconds.

Fire all 16 boosters and the 8 rockets at once, and keep the liquids at full throttle.

Wheeeeeeeee

And then enjoy what happens when those un-strutted engines run out of fuel and 'un-flex'

Just requires the wobbly rocket pack, of course

[arachnid]

Holy wow, Jarnis, that's a nice record. I'll have a go at it this evening, but I don't like my chances.

[BitPoet]

Closest I can come is 1:40 (eyeballing, of course)

stage 1 is similar, but 2x3m tanks, no solids, and there\'s a 3m Liquid engine in the center.

If you brace the 8x aero decoupelers together, you can run stage 1 at full throttle.

Stage 2 is a FL-S2000 liquid tank and a M-50 engine run as open as it goes.

[Jarnis]

Close, but...

And I must admit that this design is, mostly by accident, pretty damn good. I\'ve tried myself to find a better configuration and the problem is that this challenge is very much about carrying only exactly the weight you need while having a suitably explosive start. Since the choice of fuel tanks and engines is limited, there are not that many combinations and you just can\'t add ridiculous amounts of power without causing the whole thing to just start doing cartwheels in the atmosphere, this may be a tough record to beat 8)

[BitPoet]

Nailed it.

1:34, moving at just outside escape velocity.

Config:

CMD

tall 1M fuel tank

M-50 booster + 2x struts to fuel tank for heat disspation

Really tall separator thingy.

quad splitter.

4x tall 1M fuel tanks + M-50 boosters + struts to keep it in one piece (and bonus heat dissipation!)

4x tall radial connectors.

4x tall SRBs 2 with SAS module

Each one of those SRBs has two more hanging off it at a 90 degree angle. strut it all up to keep it in one piece.

The strategy:

All 12 SRBs + 4x LFEs are the first stage. Throttle the LFE\'s at about 60% for about 15 seconds, then firewall it. You\'ll need those SAS modules now to keep things from spinning.

When the SRBs are burnt out, drop \'em.

Dropping the 4 LFEs and igniting the final stage should be sequenced in one shot, again kept at full burn.

Done right, you\'ll top out at almost exactly escape velocity.

[Jarnis]

Tsk, tsk... 'pics or didn\'t happen'

[andydouble07]

2:55 w/ stock only