How to Jet into Orbit

[krill]

This is probably something that's been done many times before, but I'm kinda curious and don't know how to use search.

So the other day I was messing around with jet engines. I'm trying to build something extremely compact, with very few parts, that minimally relies upon rockets in order to achieve orbit. At this point, I have a tiny launcher that will get up to ~114km on jet engines alone. It's 28 parts, including the launch scaffolding. It can reach about 1300 m/s before the engines cut out due to lack of oxygen. Still trying to find a way to add rocket fuel, a rocket engine, and get it into orbit.

Any ideas, comments, suggestions, etc. appreciated!

[SalmonellaDingDong]

If you can make a 114km apoapsis, why not just stick some small SRBs or those tiny orange radially attachable engines on? Also, the HOME radial engines would be very useful here too.

What exactly are you asking us?

[UmbralRaptor]

Replace the centerline jet engine tank with an FL-T400, and add a few 24-77 radial engines?

[iDan122]

A rocket engine is necessary, otherwise you won't get an orbit

[Ruedii]

You could try to get some lateral velocity while you are still climbing. That could theoretically put yourself in orbit.

[OdinYggd]

It isn't really possible to enter Kerbin orbit without using a rocket of some type to raise your periapsis out of the atmosphere.

However, if you can reach escape velocity using your turbojet bundle, you can indeed enter solar orbit on jet propulsion only.

[UNSC]

*Cough* RCS will do it *cough*

[Brotoro]

*Cough* RCS will do it *cough*

You mean little rocket engines? Sure, that could do it.

[SalmonellaDingDong]

Brotoro that post makes me want to hugely scale up the RCS pods and make a HUGE rcs ship

[TooManyErrors]

It isn't really possible to enter Kerbin orbit without using a rocket of some type to raise your periapsis out of the atmosphere.

What about using the Mun to alter your trajectory? You could make an orbit by using a gravity assist.

Edited April 22, 2013 by TooManyErrors

[tavert]

The max surface speed at which the turbojet generates any thrust is 2400 m/s. If you somehow had infinite intakes with zero drag so you could get up to this speed purely on jets at the very top of the atmosphere (69078 m), your orbital speed would then be 2594.6 m/s (flying east). Using planet.determineOrbit from https://github.com/numerobis/KSP-scripts, that would give an orbit of 577738 by 69078 m. You're not escaping Kerbin or hitting the Mun's SOI with that. Would be interesting to run the numbers for Laythe though, see if getting back into a Jool orbit only on jets is possible...

More realistically, for best results use 1 jet and a total mass of no more than 10 tons. You can use more jets for heavier rockets, but flameouts will cause you to lose control - unless you use MechJeb 2's anti-flameout feature. Add a bunch of ram air intakes (use cubic octagonal struts to mount them), aim for level flight around 35-40 km altitude. Keep a close eye on the engine, kill the throttle immediately if it flames out, that'll bring it back online and you can feather the throttle back up to just less than what you previously were using. With this technique you should be able to get "orbits" of 100 x 40 km, then you only need a tiny rocket burn at apoapsis to bring Pe > 70 km.

Edited April 22, 2013 by tavert

[iDan122]

What about using the Mun to alter your trajectory? You could make an orbit by using a gravity assist.

Oh yeah like the Mun is in a 70 km high Kerbin orbit (facepalm)

[SunJumper]

Raising your periapsis from 40km to 70km will cost barely 50m/s, as another said, you can do it with RCS. Interestingly, you can also probably do it with ions.

[Piggius_Max]

http://forum.kerbalspaceprogram.com/showthread.php/25720-Physics-Question-Regarding-Lowest-Point-in-an-Orbit-and-Highest-Point-of-Burning

This pretty much explains how getting into orbit with jets alone is impossible, some small radial engines at Ap would get you into orbit just fine, or even RCS!

[CalculusWarrior]

Raising your periapsis from 40km to 70km will cost barely 50m/s, as another said, you can do it with RCS. Interestingly, you can also probably do it with ions.

Ion would be an interesting solution, as the engine and xenon canister doesn't weigh much, but provides quite a bit of delta-v. The problem is keeping your periapsis high enough, so that you don't fall back to Kerbin while thrusting.

[tavert]

It's also annoying to have to carry huge solar panels and make sure your apoapsis ends up on the day side. Jet ascents can cover a significant fraction of the circumference of Kerbin before getting into space. The small orange radial engines (Rockomax 24-77) are great for small maneuvers, and they don't weigh much at all.

[Creeperchair]

You can't Jet into a permanent orbit. However, if you were to have enough thrust, you could get to a solar orbit. I have done it on accident with a modded craft using Intstell radial scramjets and OPT turboramjet.

[problemecium]

You could perhaps jet into an unstable orbit with a high apoapsis and a periapsis inside the atmosphere but above the despawning line, then abuse physics warp while in space to conveniently nudge your eccentricity until your orbit becomes stable.

But that would be cheating ;P

[RyanRising]

Whoa. A thread from April 2013 has resurfaced out of the depths.

Also:

But that would be cheating ;P

Ahaha, cheating.

In fact, this thread was made before my join date!

EDIT: However, I could have sworn that my account join date was somewhere in April 2013, not August.

Edited August 30, 2015 by RyanRising

[DuoDex]

Right. Thread will remain open, as initial so-called "necro" was a valid remark.

PSA : for prompt and efficient necro-attention, please click the "Report" button on the offending post. A moderator will be on the scene shortly. And whatever you do, don't call it out in-thread, as this does absolutely nothing.

[cantab]

There used to be tricks using intakes to store air. But in any case everything in this thread is obsolete. The jet engines now have a "hard" altitude limit that can't be overcome by air hogging.

[Nothalogh]

You can't Jet into a permanent orbit. However, if you were to have enough thrust, you could get to a solar orbit. I have done it on accident with a modded craft using Intstell radial scramjets and OPT turboramjet.

Not totally true, as one of the previous posters mentioned, an atmospheric ejection into a lunar gravity assist would put you in a stable kerbin orbit

[Varsi]

Not totally true, as one of the previous posters mentioned, an atmospheric ejection into a lunar gravity assist would put you in a stable kerbin orbit

Even if this was possible I wouldn't call it stable as you'd hit Mun's SOI again after some orbits and either get flung back at Kerbin or to some other orbit.

[Kuu Lightwing]

There's a song about this thread.

[Michael R]

I wonder if you could apply enough decoupler ejection force to raise periapsis out of the atmosphere.