Achieving orbit without rockets?

[700NitroXpress]

So I have a plane that can go about 2200 m/s under 30,000 meters, which is basically orbital speed. In the map view I have an orbit, but the peri and apoapsis aren't high enough yet to make an actual orbit possible. This leads me to the question: Would it be possible to build a plane that can achieve orbit without the use of liquid fuel oxidizer systems, or SRB's?

Maybe using RCS, or Ion engines after a high enough altitude is achieved?

All stock parts and no mods or mod parts by the way.

Here's what I have so far without the use of rockets. Entirely jet propulsion, liquid fuel only.

Edited November 20, 2013 by 700NitroXpress

[rpayne88]

You can't get into orbit without burning at apoapsis This is because your current altitude would eventually become your periapsis, and your Pe would still be in atmo. Since apoapsis would be outside of the atmosphere, you would need either liquid fuel+ oxidizer, solid fuel, or RCS. It should be doable if you do indeed allow yourself to use RCS, but you are going to need to get your craft very high to have enough time to thrust your way into orbit.

[RadHazard]

Getting your Apoapsis outside the atmosphere using only jet engines would be quite the challenge. Jets stop working well above 25km or so, but you still get significant atmospheric drag up until the 30-35km range. If you manage to get that, however, it wouldn't take much dV to circularize since you're already going almost orbital speed already.

It looks like you're close to that point already with your jet already, but I imagine those last few hundred m/s you need are probably going to be significantly more difficult to get using jets only.

Edited November 20, 2013 by RadHazard

[700NitroXpress]

Well, you guys will see that the orbital speed is displayed in the info tab and the current readout is the surface speed. So my true orbital speed is actually 2385.4 m/s. I do plan on attempting it with the smallest amount of RCS I can squeeze on there. I should also say that I was running the engines at max power the entire time. If I were to dip down to about 25,000 meters, I get a lot more thrust and barely any drop in speed, then if I nose hard up to about a 45 degree angle or better, I can get the apoapsis over 45,000 meters. Now, at 45km I'm not going to get any air intake at all, but with the RCS system, I think it may be possible to accelerate just enough to get the peri and apoapsis equal or swap so the apoapsis grows to over 70km. As long as the apoapsis gets over 70km and I have RCS left over, I should be able to achieve orbit without additional propulsion systems.

At least, that's the current plan. Even at 30km and over up to 35km I can get enough air intake to run the engines at 25%.

The reason I ask and post this also, is because if it is indeed doable, I would like to make this a challenge in the challenges thread.

[Teirusu]

Short answer: Yes

I've seen a video of a spaceplane that has done exactly that with stock ion engines. (It ended up going to Eve too) I have built a smaller plane in the past that, much like yours, managed to build up enough speed to bring up its periapsis above Kerbin ground. Although, it could only do this much higher up, like well over 40KMs. Up there, the air is so thin that you only need just a tiny amount of thrust to combat air resistance. Which is fortunate, because you only get just a few K-newtons from the turbojet engine up that high.

In anycase, once you've managed to get your speed that high, all you need is a tiny extra kick (Continuous tiny kick) to bring the opposite side of your orbit above the atmosphere and to combat the small amount of drag you encounter until you get there. The problem you end up running into is the mass of the extra equipment you have to carry along to do this. Drag in stock KSP is calculated in large part by the mass of the parts. So, the heavier the parts, the more drag they create. Full fuel tanks generate more drag then empty ones, etc.

So, its possible, yet exceedingly tricky and frustrating to get the right balance to make it work properly.

[700NitroXpress]

Short answer: Yes

So, its possible, yet exceedingly tricky and frustrating to get the right balance to make it work properly.

Very interesting, now I have to try it. I'm wondering tho. Would it be easier to do with an RCS system or with Ion engines?

Also, even if there was increased weight and increased drag. Wouldn't the amount of lift and increased thrust from more engines counteract those?

[Johnno]

Possible yes.

Here's a manned Duna landing and return mission courtesy of metaphor, utilizing jet + ion engine for Kerbin orbit.

[700NitroXpress]

Possible yes.

Here's a manned Duna landing and return mission courtesy of metaphor, utilizing jet + ion engine for Kerbin orbit.

Cool stuff. What I'm seeing is lightweight designs tho. I wonder if this is still possible with my full sized pane. I don't need all the fuel that I have packed on there, so I can lighten the load and keep the same amount of thrust. Adding an RCS system would be lightweight enough. Ion engines I'm unsure about. Ion engines are always good for lightweight craft, but for a plane, I don't think they'll work very well without a lot of them. I won't have enough time to leave them on because I'm still in the atmosphere. RCS seems the logical way to go.

So if I accomplish this, I'm going to make it a challenge in the challenges thread. It has to be a stock plane design tho. No engines other than jet engines and Ion or RCS.

[allmhuran]

Strictly no, in the sense that when going from suborbital to orbital, your periapsis cannot be any higher than the highest point at which thrust was applied.

In other words, you must have something that can provide thrust in space if you want to have an orbit with its periapsis in space.

However, as you say, if we allow things like RCS and ion engines, or physics hacks like storing air in air inta or exploiting momentum via fuel transfer, then yes, certainly.

Edit to correct the first line, which was completely misleading.

Edited November 20, 2013 by allmhuran

[700NitroXpress]

Strictly no, in the sense that the highest point of an orbit will always be the highest altitude at which thrust used to achieve it was applied.

In other words, you must have something that can provide thrust in space if you want to have an orbit with its periapsis in space.

However, as you say, if we allow things like RCS and ion engines, or physics hacks like storing air in air intakes or exploiting momentum via fuel transfer, then yes, certainly.

Yeah, no hacks, but RCS and Ion engines, I'm currently experimenting with.

[nhnifong]

I've seen a single stage jet and ion plane that can get to Laythe's surface and back to Kerbin. I can't remember the source but I'm just going to take a wild guess and say Metaphor did it.

[Teirusu]

Challenge: Done

Here's the results of my test run. This was just a basic jet, no added propulsion systems. It was rather encouraging, to say the least. Please excuse my RemoteTech network

Did the same thing both runs, did a sort of powered skip out of the atmosphere. Climbed steeply at the start, until my apoapsis was about 55km, then thrust horizontally until I reached my apoapsis. After, I pitched the nose up about 15-20 degrees as I dived back through the atmosphere and picked up speed. Once I got low enough, aero-dynamic lift eventually kicked back in and I started to gain altitude once more. My test run here was nearly perfect; regained lift around 25km and lost nearly no speed due to drag and sped up even faster, easily hitting orbital speed. At which point, I just pointed prograde all the way out of the atmosphere. Let Mechjeb handle the throttle so that wouldn't flame-out, which allows one to run the jet all the way to the edge of the atmosphere.

Resulting orbit: 143 and 30km

Would easily take only a small amount Delta-V at apoapsis to raise up the periapsis. So, I slapped on some mono tanks and 6 linear RCS thrusters on the back. This time, I fell too low in the atmosphere during my dive and lost a bit of speed. I had gone up too steeply and had the extra mass of the mono-tanks, causing me to drop to around 17km. Fortunately, I still managed to gain enough speed to rocket out of the atmosphere.

Resulting orbit: 101 and -4.4km

Still respectable, only needed 33 units of mono-propellant to raise my periapsis to 75km.

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[700NitroXpress]

Yeah, you got to get that full orbit in space. 70km minimum at both ends. Very good run though.

[sgt_flyer]

Wouldn't it be possible to get to kerbin escape velocity while in atmosphere ? There has been some extremely fast hypersonic planes made (would still need to reach at least 3400 / 3500 m/s of speed in atmo, i don't know if stock engines can pull that off)

Edited November 20, 2013 by sgt_flyer

[Teirusu]

Yeah, you got to get that full orbit in space. 70km minimum at both ends. Very good run though.

As what the others pointed out before, you can't do that with jets alone. Your periapsis will -always- be inside the atmosphere with pure jet power because your reaction mass isn't really the fuel.. its the air itself. In a way, you can think of it as a ramp. You can use it to rocket yourself out into space, but you'll eventually come back down into it. Thus, you always need something else to raise your periapsis out of the atmosphere.

I suppose what you're asking for is slightly different then what I just showed you. Are you thinking of just.. slowly spiraling out of the atmosphere, trying to keep your AP and PE nearly the same the whole time? That would be quite hard.. and looooong, and you'd certainly would have to use ions engines to do it. You wouldn't be able to carry enough mono to do it.

[700NitroXpress]

As what the others pointed out before, you can't do that with jets alone. Your periapsis will -always- be inside the atmosphere with pure jet power because your reaction mass isn't really the fuel.. its the air itself. In a way, you can think of it as a ramp. You can use it to rocket yourself out into space, but you'll eventually come back down into it. Thus, you always need something else to raise your periapsis out of the atmosphere.

I suppose what you're asking for is slightly different then what I just showed you. Are you thinking of just.. slowly spiraling out of the atmosphere, trying to keep your AP and PE nearly the same the whole time? That would be quite hard.. and looooong, and you'd certainly would have to use ions engines to do it. You wouldn't be able to carry enough mono to do it.

Well, you have the best shot at this so far because your plane got a high enough apoapsis. I wasn't asking about pure jet power. I was asking if it could be done with jet power and RCS or Ion engines in combination with jet power. No rockets or SRB's, but RCS and Ion engines along with the jet engines.

So, if you had RCS or an Ion engine system on your plane, could you get it into a full orbit at 70,000 meters minimum on both ends?

That's the challenge.

[700NitroXpress]

Wouldn't it be possible to get to kerbin escape velocity while in atmosphere ? There has been some extremely fast hypersonic planes made (would still need to reach at least 3400 / 3500 m/s of speed in atmo, i don't know if stock engines can pull that off)

Without rockets, this would be hard. Even with an extreme air intake system, this may not be possible. The plane would have to be ultra lightweight, have a huge amount of air intake and at least 8 turbojet engines. Getting a jet to escape velocity would need to be done at 20km minimum because you would only have between 20km and 40km to work with before you can't run turbojets.

[DrMonte]

Would it be possible to reach Mun's sphere of influence with only jet engines? Meaning you should precisely pull up your apoapsis from atmosphere to reach it. This way you wouldn't need additional engines to pull up periapsis as it will be changed by gravity assist of the Mun.

But I'm afraid you'll need much more than jets maximum 2400m/s (+174.53m/s Kerbin rotation).

[700NitroXpress]

Would it be possible to reach Mun's sphere of influence with only jet engines? Meaning you should precisely pull up your apoapsis from atmosphere to reach it. This way you wouldn't need additional engines to pull up periapsis as it will be changed by gravity assist of the Mun.

But I'm afraid you'll need much more than jets maximum 2400m/s (+174.53m/s Kerbin rotation).

This would be brilliant if we could do it. This is officially a challenge now. But since we haven't actually succeeded in any of it yet, we have first prove if it's doable. I think you're onto something with this.

[allmhuran]

With RCS, orbit is fairly straightforward (see vid, I circularize above 150k and could easily push that higher, plenty of mono left)

Getting to the Mun shouldn't be overly difficult, especially if you add a few ion engines and a decent amount of patience. But there's definitely no way to get anywhere near the Mun on jets alone, as DrMonte says the maximum surface speed jets will provide is 2400 m/s, above this they provide no more thrust. You need to hit closer to 3000 to reach the Mun.

http://youtu.be/RVpfJlcaIcY

[700NitroXpress]

With RCS, orbit is fairly straightforward (see vid, I circularize above 150k and could easily push that higher, plenty of mono left)

Getting to the Mun shouldn't be overly difficult, especially if you add a few ion engines and a decent amount of patience. But there's definitely no way to get anywhere near the Mun on jets alone, as DrMonte says the maximum surface speed jets will provide is 2400 m/s, above this they provide no more thrust. You need to hit closer to 3000 to reach the Mun.

Impressive, well done sir!

What's the weight stats on that plane and part count?

By the way, the challenge has just been created in the challenges thread.

Edited November 20, 2013 by 700NitroXpress

[allmhuran]

Here's an ion extension of that: A tiny RCS stage to get into kerbin orbit at 150 km, then 4 ion engines with about 3000 m/s of dV, which is enough to get pretty much anywhere (easily enough if you gravity assist), and enough solar panels to keep them running just about constantly while you're in the sun. TWR is only 0.05 though.

Replace the manned pod with a probe and the TWR and dV will of course shoot up quite significantly.

Edit:

I'll get stats on the other plane tomorrow AM, I've shut the game down and it's bed time. Long story short about 20 air intakes, so at a guess part count is about 50. When building planes always use the fuselage piece that I used, not the cylindrical ones. These ones have lower dry weight despite having higher capacity.

Edited November 20, 2013 by allmhuran

[700NitroXpress]

Interesting designs, very cool stuff. Check out the challenge I made for this in the challenges thread, I think you'll do well.

[arq]

If you're using RCS, why not just put on a small fuel tank with an LV-1 or 24-7S? They have higher ISP, so it could actually be lighter than using RCS. Ions have higher ISP, so it would make sense to use them, but that would prevent you from actually landing and returning from anywhere except Laythe and maybe Gilly.

It would also be conceptually possible to reach orbit using just jets on the craft and a Kerbal to push it out of atmo at apoapsis. Or by spinning some fuel tanks while moving fuel between them. Anything that provides dV could do it.

As others have said, you will never hit Mun on just jets. They cap out at 2400m/s.