One touch return

[KatzOhki]

I was thinking of building a single stage all at once return from the mun ship. Sort of an emergency escape all the way back to Kerbin. My plan is that it has to work in a single button press and then land on Kerbin. My plan at the moment was to land a small SRB with a single man lander can attached with a parachute. What do you guys think? Cool idea? Even possible?

[arq]

It's possible, but unless you're gonna use kOS or some scripting system, you're going to need to time that single button-press correctly so that it sends you back on a Kerbin intercept.

[Rhomphaia]

It would be possible... Launch point on Mun is going to be critical though.

Edit:Scratch that... Read Base instead of ship

Edited October 10, 2013 by Rhomphaia

[Arbolus]

You would have to wait until you're near apoapsis for the SRB to be most effective, but yes it should work. You could get there, point retrograde, and then use a single actiongroup to decouple the rest of the ship, fire the SRB and activate the parachute all at once.

Only problem I can see is that a close fly-by of the Mun will affect your trajectory. If you pass it on the correct side then you'll lose speed anyway. If you pass it on the other side you'll gain speed and there's no guarantee that the SRB will be enough to save you. So, if you're heading for the wrong side, it might be best to fire early before the Mun has a chance to ruin the escape.

[Spyritdragon]

Im afraid its not possible as an emergency escape method since where you end up is heavily dependent on where you start, which constantly changes as the body you're on rotates.

[Rhomphaia]

Im afraid its not possible as an emergency escape method since where you end up is heavily dependent on where you start, which constantly changes as the body you're on rotates.

If you are talking about Mun surface though, the fact that it is tidally locked, means that as long as you picked the right launch site, then timing would be irrelevant.

[KatzOhki]

Hmmmmm... Let me clarify a bit. I want to launch from a landed position. Since mun is tidally locked I'm thinking I can select a position on the surface that will get me the return I want.

Edit: thank you rhomphia you ninja'd me

Edited October 10, 2013 by KatzOhki
Ninjas

[Cydonian Monk]

Yes, if you launch from the retrograde face of the Mun, pointed upwards, and have enough ÃŽâ€v, you should easilly be able to get back to Kerbin with a single button press.

Interesting concept, though it obviously limits your base locations. Might be more practical on Minmus.

[SunJumper]

I would presume it would involve a SRB ship tuned so that the dv is exactly what you need...

[Kasuha]

Mun rotation is bound with Kerbin similarly to how Moon rotation is bound with Earth. So if you put your base on exactly the right place and your escape vehicle at exactly the right inclination, you can have single touch to Kerbin atmosphere escape system. Maybe even to landing, assuming the atmospheric entry will not tear your already deployed parachute.

I guess one small SRB, one-man capsule and a parachute can do it - together with very precise aiming.

[SkyRender]

The main problem with this idea, of course, is that the Mun does rotate. Meaning your surface-to-Kerbin escape system would only be usable when the Mun was in the correct phase. If it weren't, you'd have a decent chance of actually going further away from Kerbin, due to how orbital mechanics work. The upshot is that you could put your base pretty much anywhere on the Mun in reality and still get back to Kerbin; indeed, you could more or less pinpoint the area you want to land back on Kerbin. You'd just have to launch at or very close to Munar dawn no matter what.

EDIT: Thinking in terms of orbits again, sorry. You'd have to fire roughly when Munar midday is fading to dusk. The basic idea is that your direction needs to be retrograde to the Mun's orbit around Kerbin; Kerbin's position in all of this is surprisingly irrelevant.

Edited October 10, 2013 by SkyRender

[KatzOhki]

Seems like it should be safe to proceed with phase 1. Phase 2 is to develop a version that launches from an angled position. I feel like that would allow for more varied launch sites.

[SkyRender]

Seems like it should be safe to proceed with phase 1. Phase 2 is to develop a version that launches from an angled position. I feel like that would allow for more varied launch sites.

As long as you can adjust your angle somewhat, you can expand the range of possible launch windows out to probably as far back as Munar dawn. I was running under the assumption that you wanted to do a straight shot from the surface, but if you don't mind performing a standard pitch-over (you'd save a bit of fuel that way anyway), you could begin from that position.

[Kasuha]

The main problem with this idea, of course, is that the Mun does rotate.

The main problem is that while Mun indeed does rotate, Kerbin still stays in the same spot on the sky for any place on the Mun. Because Mun's rotation is exactly as long as its orbit around Kerbin and in the same direction.

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[KatzOhki]

Nice illustration of the tidal lock, you should make it an animated gif. I wasn't planning on a pitch over, but having it landed in a position so that it launches directly into the correct angle. Remember, it's one-touch.

[Dkmdlb]

You could use some sort of asymmetrical weight to induce an angled descent as well. Seems like that would be the easiest way.

[SkyRender]

Yeah, don't mind my earlier ramblings. I kind of woke up sick today, so my head's not completely clear...

[Scarecrow88]

I've just had a go with a small test design, and whilst it works and got me back to Kerbin safely after a single press of the staging button to launch it, it showed me a couple of things.

Sitting at the mid point of the Mun surface, so that Kerbin is directly overhead needs a lot of DeltaV to get the periapsis down to a level where you get captured. Having a launch site east of that position requires a lot less DeltaV, but you will need to fine tune it, as it's possible to have too much. An attempt facing approximately 45 degrees retrograde had too much, and that used a FL-T200 tank and three of the small Rockomax engines - two radially mounted and one of the new in line ones. The peri came down to the surface at Kerbin, but kept going and came out the other side, way too high for a capture! For a second attempt from the same spot, I used a FL-T100 tank and just 2 of the radially mounted baby Rockomax engines, and it worked a treat. Both power designs were attached to a one man lander can fitted with two radially mounted parachutes, the skinny ladder, and three micro landing legs.

[KatzOhki]

I've just had a go with a small test design, and whilst it works and got me back to Kerbin safely after a single press of the staging button to launch it, it showed me a couple of things.

Sitting at the mid point of the Mun surface, so that Kerbin is directly overhead needs a lot of DeltaV to get the periapsis down to a level where you get captured. Having a launch site east of that position requires a lot less DeltaV, but you will need to fine tune it, as it's possible to have too much. An attempt facing approximately 45 degrees retrograde had too much, and that used a FL-T200 tank and three of the small Rockomax engines - two radially mounted and one of the new in line ones. The peri came down to the surface at Kerbin, but kept going and came out the other side, way too high for a capture! For a second attempt from the same spot, I used a FL-T100 tank and just 2 of the radially mounted baby Rockomax engines, and it worked a treat. Both power designs were attached to a one man lander can fitted with two radially mounted parachutes, the skinny ladder, and three micro landing legs.

Thank you! Awesome information.

[SkyRender]

If you don't mind positioning your craft at an 80-degree angle or so, you should be able to cut the required delta-V down by quite a lot. Fighting gravity is a dV-losing proposition no matter what you do.

[dharak1]

If you look down at the center if the system from kerbin's north pole and with the mun at the bottom of the screen to go straight up and go to kerbin you would have to be on the left side of the mun. I think.

[katateochi]

A one touch system is certainly possible, I often do single burn returns from Mun, but after seeing this post I thought I'd also make a one touch return pod.

If it's parked on a heading of 90 degrees @ 1-32.24 North by 2-32.26 East (or somewhere around there) then all you have to do is put its legs down so its pitched to about 15 degress, turn on SAS and hit launch (timing is not important). Without any other control needed it will return to Kerbin. You do then need to drop the booster and deploy chutes, but other than that its a fire-and-forget solution.

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The launch platform does have a habit of hitting the pod as it departs but that isn't a problem (aside from that the launch platform gets smashed up).

The RCS tanks are just to add some weight and a pair of septrons helps reduce the impact with the launch platform. The wings are just to make it look cool (a mandatory feature).

Here's the craft if you want it, it's totally stock.

I have to confess (please don't kill me) that I hyper-edited it into place for this test. But its less than 10tons so it will be easy to make the LV for it.

I first tried it with the one man pod but the small SRB was way too powerful and it would overshoot. I tired using a shed load of septrons but it wasn't great and actually took a lot of septrons to work. So I went for the 3 man pod to make it heavier and hey, now your friends can escape with you!

[KatzOhki]

Wow katateochi, I think you really nailed it! Pretty much perfect. Btw, I watched your vid, cool to see that Kerbals are Sennheiser fans too.

I gave it my own shot. It more or less worked, but with a few problems. Since I only had the 1 man lander can, the delta-V was way too high (predictably) so the aim had to be pretty perfect. With my landing location (-0.68,110.58), I had to get the craft between 5-10 degree East towards 90 degree heading. I forgot the moon is not a perfect sphere heheh. Here some pics:

Reentered the atmosphere going faster than 4km/s, landed about 26 km from KSC!

[Psycix]

I did this last night, around the same time katateochi posted his.

I was surprised to see we have such similar designs!

The difference is that I went with a straight up vertical launch.

This was launched from 0*N 81* W (might be E, just pick the one that faces kerbin)

Plain luck caused me to splash down no more than 25KM away from KSC!

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[samstarman5]

Doing it in one function is possible, but you will likely be coming in so steep that re-entry would be too steep(as the examples immediately preceding this post tell). Something we need to start to consider as heat effects feels like it is just around the corner.

In real life such a function would include an entire program of different maneuvers that would be possible in KSP, with enough coding in a mod. It can even be done with action groups though that would take away the automatic sense of the function.