Escape Trajectories

[rpedrosb]

Hello community,

I am fairly new to the game. I've started the career mode and at this point I have several missions in which I have to take some equipment into a scape trajectory. I was wondering what is your opinion in such missions, cause as far as I know, this would imply losing a pilot.

What's the difficulty of these kind of missions? A fast calculatino gives me an escape velocity of v = sqrt(GM/r) = 3430 m/s. I could just design a rocket with such deltaV (with margin for drag and gravity) and that would be it.

Would the cost of the mission be higher than the rewards?

Could I just add a Solid Booster as last stage, so I can reverse the trajectory and end up again landing on Kerbin? Is this feasible? Mainly because I don't want to lose a pilot with a mission like this and also because I still don't have the expertise to perform a rescue mission at this stage.

Cheers

[Deddly]

Hi, rpedrosb! It's nice to have you with us! Your question seems to belong in "Gameplay Questions", so I moved it here. I hope you don't mind.

As for your question: I think all of your ideas will work, but remember that you don't have to use a pilot at all. If you use a probe core, (see the link) you should still be able to control the rocket with no problem, and you won't need to send a pilot

 

 

[bewing]

On an escape trajectory anywhere near Kerbin, your rocket will still have an upward velocity on the order of 3000 m/s. So stopping would require an additional 3000+ m/s of dV. That kind of dV takes quite a bit of mass, and launching such an upper stage to an escape trajectory would be very expensive early in the game. As Deddly said, a probe core is the correct answer. It makes your rocket into a robot. The probe core probably needs an antenna and some solar panels,  so that it has a long life -- and can send back science reports from beyond Kerbin, for science points.

 

[Superfluous J]

Actually an escape trajectory can be gotten and escaped from with scant little fuel expenditure. You don't need to be moving UP at 3000 m/s, just moving (roughly) 3000 m/s in LKO to escape.

Here's in-game the best way to do this. With patched conics (level 2 tracking station) you can SEE it, but even without you can do it by watching the contract itself.

1. Get into LKO. Obvi.
2. Burn forward full throttle until your orbit is a wide ellipse that stretches out past Minmus. At this point, you may actually just accidentally go into "escape" trajectory because a tiny burn makes a big difference at this point. Either way, stop the engines.
3. Until you have an escape trajectory, burn forward slowly.
   1. With patched conics from a L2 tracking station, you can see when you have an escape trajectory. It will go from an ellipse to just about half of an ellipse with a little circle at the end.
   2. Without patched conics, just watch your contract for the "be on an escape trajectory" checkbox shows up.
4. Once you have an escape trajectory, do whatever the mission asks for. Stage the part, right click and test the part, or just have the part with you. Whatever.
5. Turn around and burn backwards until your orbit closes again. Burn until you're a bit under Mun's orbit. This will take very little fuel; about as much as it took to get to escape from Mun's orbit.
6. Warp to the high point (Ap) and burn retrograde until your low point (Pe) is at about 30-40km.
7. Come in with your craft pointing retrograde. If your pilot can do it click the "hold retrogrde" button. If not, do it yourself. Stage away everything but the command pod and parachute.
8. Enjoy the fire show, trigger the chute, and land safely.

Edited September 12, 2018 by 5thHorseman

[Snark]

On 9/12/2018 at 10:03 AM, rpedrosb said:

I am fairly new to the game. I've started the career mode and at this point I have several missions in which I have to take some equipment into a scape trajectory. I was wondering what is your opinion in such missions, cause as far as I know, this would imply losing a pilot.

Well, one option is to use an unmanned vehicle, and just allow it to escape.  That way you're only losing the vessel itself, not a pilot.  If it's a small, cheap vehicle that's designed to be expendable, it's not much loss. 

The other option is to just go to a trajectory that's barely enough to escape. Get to low orbit, then burn until your Ap rises just high enough to touch the SOI boundary, and then stop burning.  There, now you're on an escape path and can do whatever testing you need-- then, when you're done with your test, you only need to thrust just a little bit to reduce you below escape velocity.  (You only need a teeny burn because you were only going just a teeny bit faster than escape speed.)  Once you've done that, you're no longer on an escape trajectory, so you just coast to Ap, do a tiny bit more burn to drop your Pe into atmosphere, and then reenter as per usual.