Fastest? Smallest? Biggest? Heaviest? Not this challenge!

[EdFred]

We have always proposed and accepted challenges to do something quickly, or efficiently, or show our rockets feats of ability to lift, but this challenge is none of that. Instead, it's about how slow we can be. How is that you ask? Well here's the challenge:

With a Command Pod Mk1 manned by an intrepid, yet slow, Kerbal, obtain a Low Kerbin Prograde Orbit of 80km x 80km +/-1km, like you normally would, but be the SLOWEST to Low Kerbin Orbit. That's right, the slowest. How does one do that? That's for you to figure out!

And here's the rules because I know someone will try and be stupid about it.

Stock parts only.

No usage of the Debug Menu or other hacks and cheats.

No mods that affect the atmosphere, aerodynamics, or performance of the game or ship.

MechJeb is allowed as it does not change how the ship performs - it just automates it for you.

KER and other informational mods allowed.

FAR, NEAR, etc are not allowed.

Rockets Only

Building a plane that stays aloft for 17 hours, and then finally firing off an aerospike to finish up the orbit is not what we're going for.

No heading changes and a maximum of one circularizing burn.

You wouldn't start your gravity turn at 90 and then change it to 270 and then back to 90 on a normal launch, so you won't for this challenge either. A normal gravity turn followed by a circularizing burn at apoapsis (or if it's one continuous burn that's acceptable) to finish the challenge. No re-raising your AP and PE to slow down getting to 80x80. In other words don't make a 71x71 orbit, and then a 72x72, then 73x73...up to 80x80 - or a 1000km x 1000km and lowering it incrementally. The initial apoapsis must be between 79km and 81km

and remain in that range

. Once your PE is within 1km of your AP, and above 79km - on your first (and only) circularizing burn, stop the clock. If you need to add small thrust corrections during ascent to keep the AP from dropping below 79km, that's acceptable.

There are no limits to how heavy or light you want to make this rocket, it's all about how slow you can make it go without running out of fuel before you get to LKPO.

Rules may be added if I've missed something.

Pictures, videos, and craft files encouraged.

Leaderboard

Limited Throttle

1. EdFred 13m35s

2. Pyromartian 12m02s

3.

4.

5.

Full Throttle

1. Pyromartian 12m39s

2. EdFred 11m50s

3.

4.

5.

Edited August 11, 2014 by EdFred

[ihtoit]

easy: set it up so your pad TWR is 1.01 and/or use mechjeb to lock in to terminal velocity, make sure you've got enough delta v for an extended atmospheric firing, ascent profile to 33%, set AP to 80x80 and fire.

Craft size isn't an issue, this profile is repeatable whatever the size and time to orbit is 3h48m. I've done it with a 1.077t probe and I've done it with a 1700t SSTO fuel anchorage.

[EdFred]

easy: set it up so your pad TWR is 1.01 and/or use mechjeb to lock in to terminal velocity, make sure you've got enough delta v for an extended atmospheric firing, ascent profile to 33%, set AP to 80x80 and fire.

Craft size isn't an issue, this profile is repeatable whatever the size and time to orbit is 3h48m. I've done it with a 1.077t probe and I've done it with a 1700t SSTO fuel anchorage.

Except, as your weight decreases, your TWR increases, which means your velocity increases faster, which means you get there faster, so you can, in theory, get there slower.

[ihtoit]

Except, as your weight decreases, your TWR increases, which means your velocity increases faster, which means you get there faster, so you can, in theory, get there slower.

not if you're locked to TV. Your thrust vector will be mostly pointing at stupid angles to your velocity vector just to maintain altitude, but MJ is very good at keeping throttle to barely over 1.01TWR, even when that means it's only showing 100mm/s acceleration.

[Volcanix]

A video of a rocket launching with a TWR of ~1.01 into LKO? I'm really interested on how long this video will be.

While reading your "prologue" I already thought of something like the slowest rocket.

I'm looking forward to the first competitors!

[Kasuha]

No heading changes and a maximum of one circularizing burn.

You wouldn't start your gravity turn at 90 and then change it to 270 and then back to 90 on a normal launch, so you won't for this challenge either. A normal gravity turn followed by a circularizing burn at apoapsis (or if it's one continuous burn that's acceptable) to finish the challenge.

There are rocket designs where you need to set up higher apoapsis than your target orbit to have enough time to circularize. When driven manually, you may even fall into the atmosphere again and fight atmospheric drag again to circularize. That applies particularly to rockets with low TWR. I built one such rocket for the payload fraction challenge and even flight optimizer did not find ascent path that would go just up.

Apart of that, the strategy is relatively simple. Build a rocket that can burn as long as possible while keeping enough thrust not to fall back on the planet. And spend as much time as possible in thick atmosphere with it. Even at 40 km altitude there is enough drag to keep your engines busy while slowly ascending.

[SkyRender]

You don't even need a particularly heavy craft for this. You just need to know how to feather the throttle to keep your effective lift very low, and bring enough overall fuel to account for the fact that a lot of your flight is going to involve fighting gravity. You could probably do it with a nuclear engine and a large fuel tank and just be smart about keeping thrust barely high enough to keep you going up.

[EdFred]

There are rocket designs where you need to set up higher apoapsis than your target orbit to have enough time to circularize. When driven manually, you may even fall into the atmosphere again and fight atmospheric drag again to circularize. That applies particularly to rockets with low TWR. I built one such rocket for the payload fraction challenge and even flight optimizer did not find ascent path that would go just up.

Apart of that, the strategy is relatively simple. Build a rocket that can burn as long as possible while keeping enough thrust not to fall back on the planet. And spend as much time as possible in thick atmosphere with it. Even at 40 km altitude there is enough drag to keep your engines busy while slowly ascending.

True, it was more to combat the "I'll set my apoapsis equal to that of the Minmus, and make my circularization burn on returning to Kerbin. Oh look it took me 9 days to achieve 80x80 orbit."

[EdFred]

not if you're locked to TV. Your thrust vector will be mostly pointing at stupid angles to your velocity vector just to maintain altitude, but MJ is very good at keeping throttle to barely over 1.01TWR, even when that means it's only showing 100mm/s acceleration.

I've built plenty of rockets which make orbit that never reach terminal velocity even when burning at 100%. Limiting it to terminal velocity won't do anything in this challenge. In fact if you hit terminal velocity you're already going too fast.

[O-Doc]

So, build an Eve lander and cruise at 50km AP until your fuel runs low?

[carazvan]

I can imagine the best way to do this is to make a nuke with as much fuel as you want; put it in orbit normally with Pe and Ap at just under 70km and thrust at minimum to keep it there .. then do as many orbits as you want until you get low on fuel then raise to desired altitude. Since doing a slowest ascent then becomes a matter of patience not engineering I wont be submitting an entry.

[ihtoit]

I've built plenty of rockets which make orbit that never reach terminal velocity even when burning at 100%. Limiting it to terminal velocity won't do anything in this challenge. In fact if you hit terminal velocity you're already going too fast.

You can hit terminal velocity horizontally (try going supersonic at sea level with stock everything and jets not rockets, no airhogging - it's impossible due to the game physics), it's only when you hit 30-someodd km that Vt=Vo(orbital) and your ballistic curve radius exceeds that of your altitude track (and your craft just seems to want to go up but it's not, it's following a ballistic trajectory and will eventually fall back to Kerbin). Maybe I should have put "Limit to Vt or TWR<1.01 whichever is lower". I guarantee you, no rocket will accelerate upwards with a TWR less than 1.00 and Vt on an ascending craft will ALWAYS require a TWR of more than 1.00, ergo TWR will NEVER go below 1.01 during ascent otherwise there will be a net deceleration (factoring in drag as well) which I think would actually violate the rule of the challenge.

[James_Eh]

I guarantee you, no rocket will accelerate upwards with a TWR less than 1.00 and Vt on an ascending craft will ALWAYS require a TWR of more than 1.00, ergo TWR will NEVER go below 1.01 during ascent otherwise there will be a net deceleration (factoring in drag as well) which I think would actually violate the rule of the challenge.

Disagree - during the last stages of ascent (even in upper atmosphere with a bit of drag) you can easily increase your vertical velocity with a TWR under 1. In fact that's a very efficient way to go about finishing off the orbit. It's that magical point where your AP stops rising but your PE zooms upwards.

[EdFred]

Disagree - during the last stages of ascent (even in upper atmosphere with a bit of drag) you can easily increase your vertical velocity with a TWR under 1. In fact that's a very efficient way to go about finishing off the orbit. It's that magical point where your AP stops rising but your PE zooms upwards.

This. I have had rockets with a final stage of in the 0.8-0.9 range.

[ihtoit]

your vertical velocity isn't increasing if your AP isn't increasing. If your AP is decreasing during the ascent phase, your vertical velocity is in fact decreasing. If your PE is increasing during ascent it's because your horizontal velocity is increasing.

[EdFred]

your vertical velocity isn't increasing if your AP isn't increasing. If your AP is decreasing during the ascent phase, your vertical velocity is in fact decreasing. If your PE is increasing during ascent it's because your horizontal velocity is increasing.

It's not, it's maintained.

[James_Eh]

your vertical velocity isn't increasing if your AP isn't increasing. If your AP is decreasing during the ascent phase, your vertical velocity is in fact decreasing. If your PE is increasing during ascent it's because your horizontal velocity is increasing.

Think we are talking past each other. AP can increase while vertical velocity is decreasing. Maybe I need to go back and read more carefully. My point was, during the last stages of ascent (say > 35kM Kerbin surface) a TWR of <1 is sufficient, and usually desirable. Sorry if I muddied the waters with a derailer.

[ihtoit]

think about it, the insertion burn is entirely horizontal to kick the periapse, there is no vertical acceleration in a perfect burn. The vector is at a pitch of zero. You don't need ridiculous TWR to increase PE when there is no drag to overcome, all you have to overcome is the moment of inertia which requires a TWR greater than zero. The higher the TWR is, the shorter the burn, which in this situation is an advantage because you'll just end up burning back into the atmosphere otherwise. In an efficient ascent you're already burning horizontally by the time your AP gets to altitude so you're already suborbital. If you burned vertically the whole way (or at such an angle as your horizontal velocity remains at zero) you can ascend at walking speed for as long as you've got fuel and not have to worry about dropping back down during your kick burn - all you do is increase your thrust as you heel over to maintain your vertical velocity (preferably at or near zero so you don't overshoot your target AP or fall back to Kerbin) until you hit that balance of increasing your horizontal velocity to orbital while maintaining altitude. Not an impossible task (it might be for MechJeb), but pretty intense - it's like manually balancing power to each wheel in a 4WD while driving offroad through a minefield during a blizzard. Something more easily demonstrated during a normal ascent: when you start your gravity turn, your vertical velocity starts to decrease in relation to your horizontal velocity and at some point your horizontal velocity actually surpasses your vertical - you've just gone ballistic.

[Andrew Hansen]

If someone wants to win this challenge, all they need is to build a small, minimalistic rocket, then put a pile of asparagus-staged jet fuel and jet engines under it (to last as long as possible). Then, set MechJeb to hover the rocket for as long as possible, and once all the jet fuel is gone, decouple them and head off into orbit at normal speeds. I'm sure you could make it take several hours to get to orbit.

I've never used MechJeb though, so I'm not really the guy to be doing these kinds of things.

[ihtoit]

yeah, full-on autopilot wouldn't work (just tried it with a low thrust limit, it wants to do a gravity turn before it hit AP which wrecks the attempt), you need to use SMART A.S.S. to hold it at 90 degrees pitch up and the ascent help to limit thrust (set your thrust ceiling at Vt so you don't shoot off like... a missile). Trial and error to find the thruster sweet spot there, that depends on the static TWR which of course changes all the time, and gets REALLY tricky if you're staging as well.

[Bilfr3d]

Stage your craft, make it move a little bit, set timewarp to 4x on the Launchpad. A few hours later, come back and continue the ascent as normal.

[EdFred]

Is that how you do normal ascents?

[Pyromartian]

LESS TALKY MOAR DOING! jk:sticktongue:

Lets get this started at least...

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First off I wanted to show the exact opposite, a fast (but efficient) launch.

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This is a standard launch. No gimmicks, no goofing around, and straight to the point.

This is what OP wants. Or at least it is in the spirit of it.

Stage your craft, make it move a little bit, set timewarp to 4x on the Launchpad. A few hours later, come back and continue the ascent as normal.

No move and wait.

So without further adieu...

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I set my max TWR at 1.3 and watched it fly.

12 minutes and 2 seconds with just enough Dv to de-orbit.

[thereaverofdarkness]

My submission:

http://imgur.com/MJ4Ve8Z,HwAJN2u,5kAyWjn,nYJJOjf,2pp5fF9,sO553oT#4

I put the periapsis up to 90km thinking I would need that to get into orbit but my final TWR was higher than I expected. So I let the craft fall a bit but I fell too far. Needless to say, I accidentally wasted a minute or more, but the rest of the time is legit. I didn't get into an 80x80 orbit but it would have taken another 15 minutes mission time to make that happen, so I figure something close is good enough right?

Anyway I think my valid time to orbit was about 4½ minutes. Nothing impressive, but it'll get something up on the leaderboard I suppose.

[EdFred]

I was able to get 9m34s, but then tweaked the rocket, and while burning 100% throttle the entire ascent (other than coasting to AP, I was 11minute range flying it by hand. I used MJ and limited the acceleration to 12m/s and was at 13m47s. I think I will split the leaderboard into 100% throttle, and throttle limited a bit later. There's this thing called outside I have to go experience.