Kerbol Orbit Rescue Mission

[Yutah123]

Hello everyone!

I'm using the demo version of KSP, and I got a kerbal into orbit around Kerbol, hooray! However, the mission was to get a kerbal into a somewhat low orbit, and it was pretty high, only a bit lower than Kerbin's. At first, I left it there, since it has no fuel (or engine, for that matter) and I couldn't really be bothered to make a rescue ship for him in order to redesign and retry. However, I have now decided that I want to do it properly, and for that, I need a ship capable of getting to Kerbol orbit and back.

Details

• KSP demo v1.0.0.813
• Sandbox mode
• Kerbol orbit with an apoapsis of 13,012,683km and periapsis of 12,912,697km, practically no inclination difference with Kerbin
• Craft is orbiting in the same direction as Kerbin
• Craft is ahead of Kerbin
• Single kerbal trapped in orbit
• I'm quite a new player
• Parts available in the demo here

Requirements

• Capable of getting into a Kerbol orbit and back
• Capable of rescuing a kerbal

Preferences

• A guide in how to use it (this will be really helpful, so pretty please?)
• A generous amount of extra delta-v just in case

Thanks for reading!

P.S.  If you can, a design for the actual mission to Kerbol orbit would be nice

Edited September 17, 2017 by Yutah123
Added parts available and mode

[Geschosskopf]

OK, just to make sure I understand....   You have a wreck in solar orbit a bit inside of Kerbin's orbit and you want to send another ship to rendezvous with the wreck and bring the Kerbal home.  This is fairly simple, but the rescue mission will probably take about 1.5-2 years of flight time on top of however long you need to wait before leaving Kerbin.  If you have to match planes with the wreck, it will take even longer and will require considerably more fuel, too.

What you're doing here is essentially the same thing as flying to one of the inner planets, like Eve.  The same basic techniques for timing when to leave Kerbin and how to aim at the target apply.  There are a few key differences, however.

• The wreck is a MUCH smaller target and has no SOI.  Thus, you'll have to get pointed in more or less the right direction and then make a number of correction burns as you get closer, gradually bringing your closest approach down to 5km or less.  These corrections will be weeks to months apart.
• You will have to burn to match velocities once you get close to the target, instead of using a planet's gravity to help capture.

The main question is whether or not the wreck is in the same orbital plane as Kerbin.  If it is, then things will be much easier and need way less fuel.  If the wreck is has any significant amount of inclination, then things get complicated, will take rather longer, and you'll need way more dV.

Assuming there's no real inclination difference, the fight plan goes like this:

• Wait until the wreck is somewhat behind Kerbin's position in space.
• Leave Kerbin on the daylight side so you exit Kerbin's SOI heading in the opposite direction to Kerbin's motion, same as going to Eve.  Create this escape burn node to get as close as possible to the wreck but don't waste any time and effort trying to get closer at this point than a couple thousand km at closest approach.  You'll have to tweak the closest approach over time to get right on target, as mentioned above.
• Once you get to closest approach (which by now will be 5km or less, preferrably 1km or less), match velocity with the target.  At this point, it's pretty much the same thing as rendezvousing in LKO.  Do the same procedure as in all the rendezvous/docking tutorials.  Aim at the target, burn until you're doing about 20-30m/s relative to the target, and coast.  When the target drifts too far off-center, match velocities again, point at the target again, burn a little again, and coast again.  Repeat as necessary until you're within 10-50m of the wreck.
• EVA the stranded Kerbal into the rescue ship.
• Set Kerbin as your target, create a node that gives you an encounter, and burn for home.

Off the top of my head (and my memory isn't that great), I seem to recall that the rescue ship will probably need about 3500-4000dV:  About 1200-1500 to to leave Kerbin's SOI on an intercept course, about 600-800 to fine-tune the intercept and match velocities close to the target, then another 800-1000 or so to get back into Kerbin's SOI.  If you set that encounter up correctly, you can aerocapture and then aerobrake over several orbits to land without needing much if any more fuel.  But much depends on how well you time leaving from Kerbin to minimize the fuel it takes to rendezvous, and then how efficiently you can then get back to Kerbin.

You want a long trip so you cross both the wreck's and Kerbin's paths at as shallow an angle as possible.  IOW, both the out-bound and homeward-bound trips should take about 1/2 of a solar orbit.  But that means you can't come right home again immediately.  By the time you reach the wreck, you'll be way out in front of Kerbin because you'll be moving faster, so must wait at the wreck for about 2/3 of a solar orbit to catch up with Kerbin from behind to do the burn for home.  That's why the mission will take well over 1 year to complete.

[Yutah123]

Thanks for the reply, especially the instructions. And you're right, there's practically no inclination difference with Kerbin's orbit, I'll add that detail to my post.

Thanks again!

[Yutah123]

19 hours ago, Geschosskopf said:

OK, just to make sure I understand....   You have a wreck in solar orbit a bit inside of Kerbin's orbit and you want to send another ship to rendezvous with the wreck and bring the Kerbal home.  This is fairly simple, but the rescue mission will probably take about 1.5-2 years of flight time on top of however long you need to wait before leaving Kerbin.  If you have to match planes with the wreck, it will take even longer and will require considerably more fuel, too.

What you're doing here is essentially the same thing as flying to one of the inner planets, like Eve.  The same basic techniques for timing when to leave Kerbin and how to aim at the target apply.  There are a few key differences, however.

• The wreck is a MUCH smaller target and has no SOI.  Thus, you'll have to get pointed in more or less the right direction and then make a number of correction burns as you get closer, gradually bringing your closest approach down to 5km or less.  These corrections will be weeks to months apart.
• You will have to burn to match velocities once you get close to the target, instead of using a planet's gravity to help capture.

The main question is whether or not the wreck is in the same orbital plane as Kerbin.  If it is, then things will be much easier and need way less fuel.  If the wreck is has any significant amount of inclination, then things get complicated, will take rather longer, and you'll need way more dV.

Assuming there's no real inclination difference, the fight plan goes like this:

• Wait until the wreck is somewhat behind Kerbin's position in space.
• Leave Kerbin on the daylight side so you exit Kerbin's SOI heading in the opposite direction to Kerbin's motion, same as going to Eve.  Create this escape burn node to get as close as possible to the wreck but don't waste any time and effort trying to get closer at this point than a couple thousand km at closest approach.  You'll have to tweak the closest approach over time to get right on target, as mentioned above.
• Once you get to closest approach (which by now will be 5km or less, preferrably 1km or less), match velocity with the target.  At this point, it's pretty much the same thing as rendezvousing in LKO.  Do the same procedure as in all the rendezvous/docking tutorials.  Aim at the target, burn until you're doing about 20-30m/s relative to the target, and coast.  When the target drifts too far off-center, match velocities again, point at the target again, burn a little again, and coast again.  Repeat as necessary until you're within 10-50m of the wreck.
• EVA the stranded Kerbal into the rescue ship.
• Set Kerbin as your target, create a node that gives you an encounter, and burn for home.

Off the top of my head (and my memory isn't that great), I seem to recall that the rescue ship will probably need about 3500-4000dV:  About 1200-1500 to to leave Kerbin's SOI on an intercept course, about 600-800 to fine-tune the intercept and match velocities close to the target, then another 800-1000 or so to get back into Kerbin's SOI.  If you set that encounter up correctly, you can aerocapture and then aerobrake over several orbits to land without needing much if any more fuel.  But much depends on how well you time leaving from Kerbin to minimize the fuel it takes to rendezvous, and then how efficiently you can then get back to Kerbin.

You want a long trip so you cross both the wreck's and Kerbin's paths at as shallow an angle as possible.  IOW, both the out-bound and homeward-bound trips should take about 1/2 of a solar orbit.  But that means you can't come right home again immediately.  By the time you reach the wreck, you'll be way out in front of Kerbin because you'll be moving faster, so must wait at the wreck for about 2/3 of a solar orbit to catch up with Kerbin from behind to do the burn for home.  That's why the mission will take well over 1 year to complete.

Geschosskopf, just to be clear, is this for when the craft in question is orbiting in the same direction as Kerbin? (Also, I'm assuming that the orbit around Kerbin is going the standard east)

Thanks again, by the way.

Edited September 15, 2017 by Yutah123
More information

[Geschosskopf]

1 hour ago, Yutah123 said:

Geschosskopf, just to be clear, is this for when the craft in question is orbiting in the same direction as Kerbin? (Also, I'm assuming that the orbit around Kerbin is going the standard east)

Yeah.  same direction around the sun as Kerbin and all other planets go.  If the wreck is going in the retrograde direction compared to every other planet in the system, and inside Kerbin's orbit, I first have to question how you got enough dV to get into that position to begin with.  But if you have that much dV available, then rescuing the wreck's survivors won't be a problem anyway, so why are you asking?

[Yutah123]

12 hours ago, Geschosskopf said:

Yeah.  same direction around the sun as Kerbin and all other planets go.  If the wreck is going in the retrograde direction compared to every other planet in the system, and inside Kerbin's orbit, I first have to question how you got enough dV to get into that position to begin with.  But if you have that much dV available, then rescuing the wreck's survivors won't be a problem anyway, so why are you asking?

It's going to take a lot of time for the craft to get behind Kerbin. (You can see that from the images) 

And I'm pretty sure to do it with the craft in front of Kerbin would take lots of extra delta-v, transfer orbits and all that, right?

Edited September 16, 2017 by Yutah123

[Geschosskopf]

14 hours ago, Yutah123 said:

It's going to take a lot of time for the craft to get behind Kerbin. (You can see that from the images) 

And I'm pretty sure to do it with the craft in front of Kerbin would take lots of extra delta-v, transfer orbits and all that, right?

Yup, this is the same as a transfer to an inner plant.  So you'll have to wait most of a year for the target wreck to get into proper position, or be willing to spend stupid amounts of dV to get there now, and then wait most of a year until it's cheap to get back to to Kerbin.

[Yutah123]

Well, I'll probably wait, because I'm sure that building an efficient rocket in demo is hard, what with the choice of engines.

Now, to wait for a design.

[Spricigo]

19 hours ago, Yutah123 said:

It's going to take a lot of time for the craft to get behind Kerbin. (You can see that from the images) 

And I'm pretty sure to do it with the craft in front of Kerbin would take lots of extra delta-v, transfer orbits and all that, right?

Not necessarily a prohibitive amount.  You can depart now and stabilize in a orbit bellow the target. Since this lower orbit have higher angular velocity tou will catch up with the target.

It definitely requires some extra deltaV, part of which expended far from kerbin(no oberth advantage). Also the catch-up phase can be time consuming as well. In any case the option exist.

Btw: I have an idea of the parts available in the demo.  How about limits of partcount, mass and dimensions of the vessels? 

[Yutah123]

8 hours ago, Spricigo said:

Not necessarily a prohibitive amount.  You can depart now and stabilize in a orbit bellow the target. Since this lower orbit have higher angular velocity tou will catch up with the target.

It definitely requires some extra deltaV, part of which expended far from kerbin(no oberth advantage). Also the catch-up phase can be time consuming as well. In any case the option exist.

Btw: I have an idea of the parts available in the demo.  How about limits of partcount, mass and dimensions of the vessels? 

The craft is in sandbox mode, and as far as I'm aware, there are no limits to part count, mass, dimensions etc. 

P.S. I've added a link to an album showing what parts are available in the demo in the details above, if you need to check.

Edited September 17, 2017 by Yutah123

[James Kerman]

I've had a look at the parts list you posted and had a play in the VAB.  I built a really ugly beast with 7,500 DV that will be hard to fly to orbit because the reliant engine has no gimble so use your most experienced pilot.

https://imgur.com/FK72Bzt

Another issue you will have is heat on re-entry without a heat shield.  You may need to slow yourself down through atmospheric re-entry.

You can use this tool to find transfer windows and minimise Dv requirements: http://ksp.olex.biz/

Edited September 17, 2017 by James Kerman
Edited for more information

[Palaceviking]

Buy the game,  because you're worth it

[Yutah123]

Hello everyone! I just remembered I have a somewhat powerful but inefficient (I think) rocket in my arsenal, the Direct Ascent Mün Launcher. Designed during my "bigger is best better most of the time, go smaller when it becomes too heavy" phase, it was made to go directly to the Mün without orbiting Kevin or the Mün. Do you have a couple of suggestions, or do you think it'll do the job? (redesigned with a rescue capsule of course)

Edited September 30, 2017 by Yutah123
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[Palaceviking]

I always try to orbit Kevin where possible. Otherwise yeah,  even overpowered slightly methinks.