Kerbolcentric rescue

[Xephirious]

I've seen a few different ideas on how to rescue from being stranded in Kerbolcentric orbit. I'm trying to work in the realm of reality so I'd like to attempt a rescue that doesn't take 2 years to coordinate. My plan is to grab Jeb while he is at Ap in a highly elliptical orbit from a circular orbit at the same altitude.

Imagine a Kerbin like orbit around Kerbol intersecting a comet like elliptical orbit.

I anticipate two main issues.

-Plotting the intercept

-EVA in this very short window.

My initial plan is to fiddle until I come up with an intercept of less than 200m then go EVA a bit before Ap so that I can use approach time and time on Ap for the intercept.

Jeb's getting lonely out there and his ship is running out of snacks!

Is this even feasible?

EDIT: We've lost Jeb, while 'switch(ing) to' the ship it esploded and Jeb is now somewhere in Interstellar space.

Edited December 4, 2013 by Xephirious
KSP ejected Jeb onto an interstellar course. RIP Jeb

[Francesco]

Show us some screenshots of the orbit first

Or maybe make this become a challenge! Upload the savefile and we'll have fun with this scenario

[Taki117]

For the distance you want it's going to be extremely difficult to get that close for any significant length of time. As far as rescuing Jeb it's possible, but it's going to take a very long time or a massive amount of dV. What you are trying to do is "hit a speeding bullet with another bullet whilst riding on the back of a horse"

[Soda Popinski]

After doing one of those 2 year dealies, let me tell you getting a 200m intercept will be next to impossible with a heliocentric orbit. Luckily, you don't need to. Sub 1km intercepts are only needed in the relatively small orbit you find around planets, as you get too much error trying to thrust straight while in a curving orbit. If you're going around the star Kerbol, you'll be fine with hundreds of km for an intercept, and close in using a rocket engine or RCS (divide distance by 100 to get approximate distance / second you want to close at - so at 200 km away, approach at 2000 m/s).

You won't be able to do an EVA and capture if you plan to pass by with vastly different shaped orbits with the same apoapsis, as you're relative velocities will be far too high. The above scenario means you'll be matching speeds, and hence orbital shape. This all means you don't have a short EVA window, and can take your time.

[Xephirious]

So soda says basically "bring lots of dv and do it the long way"

I'm considering an ion powered external control seat delivered by a large fast rocket that will establish the kerbol orbit.

Well, KSP appears to have saved me from this issue. When swapping to the ship in question KSP esploded it and launched it onto an interstellar trajectory that is perpendicular to the plane of the Kerbol system. I.e. Jeb is gonna freeze in interstellar space

RIP Jeb, my first and only Kerbal lost in months of playing.

http://i.imgur.com/uVu6QQv.png' alt='uVu6QQv.png'>

Screenshot of the relevant orbits.

Edited December 3, 2013 by Xephirious
KSP blew up the ship and launched Jeb into oblivion :(

[Soda Popinski]

Without lots of delta V, how were you planning on matching the relative velocities?

[Xephirious]

Hitting 'f' before Jeb goes splat? I guess the answer is I didn't plan on it and that's why it wasn't a feasible plan in the first place Maybe KSP did me a favor.

[Soda Popinski]

It's feasable, if you managed to get the rescue craft at the apoapsis right about when Jeb gets there. You would just need to burn retro about 9000 m/s I to match orbital velecities, rendezvous, then burn 9000 m/s prograde to get back to the circular orbit, then adjust your orbit to get back to Kerbin's SOI.

Sorry to hear you lost an astronaut.

[Kasuha]

The matter is, for rendezvous you need to get on the same orbit as your target. There's no way around that. Therefore you need to design a ship that's strong enough to do that and then return. That circular orbit is a reasonable starting point but with target orbit this elliptic I would probably go the other way - rise the apoapsis somewhere near Jool, match the periapses near Sun, then lower the apoapsis to get the encounter.

Those "two years to coordinate" ... if you mean real time then no, rendezvous in solar orbit does not take significantly longer time than rendezvous in Kerbin orbit. If you meant game time then again, I'm afraid it's tricky to get it below several orbits.

In Solar orbits, 2000 km is close encounter. You don't need to try getting below that. Then you switch to navball, keep markers aligned by burns to sides and keep relative velocity proportional to the distance. Above 100 km you can see the distance in the map under the target ship's icon. Below 100 km you can see it in the space view.

[Nao]

Hitting "f" in a split second that the rescue craft would not be possible. So I was thinking about another way to make the OP's rescue attempt on low dV budget. First thing that came to mind was a space cannon that could be used to bounce the free floating kerbal into rescue craft's orbit. In theory it could work for even big relative velocities as the flame had some lenght, that is if i've manage to hit him with the blast.

So I've started testing. Launched a Kerbal into circular orbit first and then launched space cannon to rendezvous at medium speed of 333,3 m/s. Unfortunately as i approached the stranded kerbal this happened:

(warning a somewhat disturbing image) That's Kelrey Kerman, a lot of them. All in a swarm that kept itself tight as my cannon flew by it. It seems like the kerbal have been infected with some kind of alien disease that mutated and reproduced him while I was busy launching the cannon into position.

Experiment results: inconclusive. Next experiment: pending. Clearing of alien infestation takes top priority.

Edited December 4, 2013 by Nao

[Kasuha]

(warning a somewhat disturbing image)

Oh. My. GOD. O_O

Edit: Idea. You can send a rescue ship with suicidal accelerator.

The accelerator would come earlier and match orbits with Jeb to prevent Kraken attack. It would bring a mainsail engine and small fuel tank. It would match orbits and rendezvous with Jeb at his apoapsis, then aim the mainsail retrograde at jeb and burn. Jeb would get kick to higher orbit while the accelerator could be steered to crash into Sun.

Then the rescue ship can match Jeb's higher orbit and finally rescue him.

The unknown here is how much of a push will Jeb get from that engine.

Edited December 4, 2013 by Kasuha

[Xephirious]

Interesting ideas! Too bad Jeb is already lost I will continue testing emergency retrieval vehicles to avoid another lost Kerbalnaught. The Union of Rogue Kerbalnaughts has threatened to strike if another Kerbal is launched onto an intergalactic trajectory.

Wooow that pic. I hope you sent your best Xeno erradicating SSTO with lots of ammo.

Edited December 4, 2013 by Xephirious
OMG that pic