Highest Apogee of Purely Jet-Powered Craft

[Geometrian]

Challenge: Using only jet/turbojet power, what is the highest apogee from Kerbin you can get (stock parts and stock aerodynamics)?

My current record

. However, I'm kinda betting that it might be possible to get escape velocity by using more jets.

Because of this, I'd like to split this challenge into two categories:

1. Using only one jet/turbojet
   
2. Using any number of jets/turbojets
   

Your craft does not have to be an SSTO, but all power in each stage should derive from jets.

Bonus: if escape velocity is indeed possible, can you get interplanetary travel using only jet propulsion? A one-way trip would be impressive enough, if only for the required precision alone--but maybe you can, for example, get to Laythe and back using only jet power?

[GigaG]

I'm going to call attention to this. It seems like an interesting challenge. I probably won't do it, but I'd love to see if anybody could go interplanetary by jet power. Laythe and back... sounds like a job for Scott Manley! (Although Joolian escape velocity done indirectly from a moon using jets seems like it would be much harder than the already-unproven task of getting out of Kerbin's SOI using jets... if Jool had an oxygen atmosphere, maybe it would be easier.)

On another note, I believe there is a bit of an exploit where jets or intakes "store" intake air and can be fired in space briefly if the jet or air intake is shut off with air in it (forgot whether it is jet or engine.) Just saying, it might be a problem to enforce prohibition of this kind of glitch.

On yet another note, if that glitch does work, I wonder if anybody could go to Minmus and back using only stored intake air after leaving Kerbin.

[The_Rocketeer]

Interplanetary, heck no!

Jets won't work in space. If u are out by a single hundredth of a second of burn, that will make a difference of thousands of kilometers on the interplanetary scale. What you're suggesting is throwing a dart at bulls-eye on a plane pulling loop-de-loops, in a strong gale, and aiming through a back-to-front telescope.

The delta-V, hypothetically, may be possible considering Kerbal physics, but the precision would be impossibly accurate, and with only jets you'd have no way to make course corrections.

It would probably be easier to attempt to hit Kerbol using only Jet power.

However...

I fully endorse the apogee challenge, or even a mun fly-by-and-return. And if anybody wants to prove me wrong, I will be the first to hit the +rep button.

Edited November 28, 2014 by The_Rocketeer

[Superfluous J]

Well if you allow monoprop to make course corrections, then the "only" problem is getting enough dV to get close and then tweak it.

[Lesbiotic]

The main problem is that turbojet thrust drops to 0 as you approach 2400 m/s, meaning that reaching escape velocity alone is more or less impossible with jets, regardless of the number of engines used. Doing closed intake jetting at lower speeds outside of the atmosphere would work in theory, but the number of intakes required to get anywhere is completely mind boggling.

[Laie]

The delta-V, hypothetically, may be possible considering Kerbal physics, but the precision would be impossibly accurate, and with only jets you'd have no way to make course corrections.

You won't reach escape velocity, as has been discussed here: http://forum.kerbalspaceprogram.com/threads/96389-Basic-Jet-Escape

Ramjets approach zero thrust as the surface speed goes towards 2400m/s. So the highest theoretically possible orbit would have like 2600m/s orbital velocity at a <70km periapsis. That's too little to even reach the moon for a gravity assist.

[Tsevion]

Well, without putting much effort in, this is

I make it to 348,800m.

I say not much effort because literally all I did was take my in atmosphere speed-runner (2336m/s under 40km), point it straight up, max the throttle and hit space.

As several people have mentioned, theoretical max top speed in atmo is 2400m/s, and getting over 2300m/s is tricky. After that it's just fine tuning, but that won't make it a whole lot higher than this... I'm guessing around 500km is the cap... so don't expect any jet powered Mun runs.

This old Reddit challenge may also be enlightening.

With a little more effort (and a lot more air intakes), I was able to do this:

That is 415,700m... as I said, I'm guessing around 500km is the ceiling.

[Rhomphaia]

Highest theoretical altitude should be 872535m

[Jouni]

I got 449,433 m. I'm not sure what's the optimal number of intakes, and whether throttling down can help.

[The_Rocketeer]

Well if you allow monoprop to make course corrections, then the "only" problem is getting enough dV to get close and then tweak it.

I think the mass of the monoprop would have very negative on the crafts acceleration potential.

The thrust issue isn't a problem if you've hit a high enough acceleration rate early enough, but doubtless there are absolute mathematical limitations based on scaling drag though.

So, no, throttling down won't help at all. You need to get REALLY fast REALLY soon.

There'd be no sense in flying an orbital ascent - your only hope would be a vertical ascent and hoping it went high enough.

If you could get high enough for a grav assist from Mun, it could take you much higher.

Edited November 28, 2014 by The_Rocketeer

[Geometrian]

I have discovered something interesting: if you enable infinite fuel, jets work in space. They have around 1kN to 3kN thrust.

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[Starman4308]

I have discovered something interesting: if you enable infinite fuel, jets work in space. They have around 1kN to 3kN thrust.

So that must be why I keep on getting "test Basic Jet Engine on Minmus" contracts. The Kerbals at C7 Aerospace are all playing KSP with infinite fuel turned on.