Help Bring Jeb Home: 1072 Delta V in the Mun's East Crater

[0Kev]

I got a bit greedy for science points after having Jeb land in the highlands just north of the east crater. If I had him fly home from there, probably fine!

But, I did not realize how much fuel would be needed to make the hop, so now it's a tight margin to bring Jeb back to Kerbin.

I suspect it's possible with some trick flying, and if anyone can do that, it's Jeb. He just needs some feedback from engineering.

He's very near the middle of the north-most rim of the east crater.

My last quicksave is at the apoapsis of the suborbital trajectory flying southwest from the original landing spot, 23.5 km NE the current position, with around 140 more delta v. If that happens to be useful.

1072 delta V remaining, per Flight Engineer chip.

The ship weighs 10,118 kg, including 222/272 units of fuel/oxidizer.

It has 102 units of monopropellant, and it's RCS thrusters are just shy of enough power to lift off by holding H.

Edited April 21, 2014 by 0Kev

[sewerbird]

Don't really see the issue: you're roughly equatorial, and it takes about 850-900ish dV ime to get back to Kerbin. Particularly with the RCS, you should be able to trim your return trajectory into Kerbin's atmosphere just fine.

[Rokker]

burn up quickly and then as soon as possible burn 90 headin 0 pitch into orbit, then experiment from there, thats all I can give ya, maybe send a rescue craft and transfer all the science over.

Edited April 20, 2014 by Rokker

[Scotius]

It will help if you perform return burn to Kerbin retrograde to Mun's orbit. It seems counterintuitive, but you don't want to gain even more speed - it will result in a high Kerbin orbit (very similiar to Mun's). Enter Mun's orbit normally, but set return maneuver node when your ship starts moving from east to west (basically it will be between Mun and Kerbin). It will result in lower overall speed, which will drop your periapsis low over Kerbin. Then small correction burn will alow you to bring it into atmosphere for aerobraking. 34 -35 kms over Kerbin should bring your apoapsis to about 200 kms.

[0Kev]

Don't really see the issue: you're roughly equatorial, and it takes about 850-900ish dV ime to get back to Kerbin. Particularly with the RCS, you should be able to trim your return trajectory into Kerbin's atmosphere just fine.

Perhaps I don't know the most efficient manner to do it.

burn up quickly and then as soon as possible burn 90 headin 0 pitch into orbit, then experiment from there, thats all I can give ya, maybe send a rescue craft and transfer all the science over.

Ah, this simple explanation helps a lot. I'm in Munar orbit now and was able to tweak nodes to get home with fuel to spare. Executing...

[Rokker]

yup, the sooner you are pointed parallel to the surface, the sooner your engines arent fighting gravity. when you are pointed straight up, your engines are sacrificing x amount of their acceleration to gravity so when the body doesnt have an atmosphere, the sooner you can point parallel, the better.

[MarvinKitFox]

It has 102 units of monopropellant, and it's RCS thrusters are just shy of enough power to lift off by holding H.

Small tip:

If you have both RCS fuel, and a more efficient engine,

use the RCS fuel as soon as possible, to augment your normal thrust. (i.e. take off with normal engines *and* rcs H)

You gain more by using it early, thus decreasing its mass, than by lugging it along all the way. 102 units for a 10-ton lander is a LOT. In your case, it's good for another 108m/s delta-v, and the loss of its mass will boost your main fuel supply's delta-v by about 48 more. (depending on your engine isp, I have to guess your lander main engine type, but it looks like a 370 ISP engine to me.)

Difference between 1072 d-v and 1072+108+48=1228 is a LOT!

Of course, your original 1072 is plenty enough to get back home from Mun, even from a low-altitude polar crater.

P.S. Almost enough RCS thrust to hover on Mun? Have you seriously put 16 RCS on one Mun lander? Wow, no wonder you need so much RCS fuel!

Edited April 20, 2014 by MarvinKitFox

[0Kev]

And, home. THANKS!

[Tollazor]

I had a very similar situation. I ended up burning up from mun and out and entered into a really huge oval with the aposis out above minmus. When I hit aposis I was traveling about 20m/s, tiny little burn and I just let myself fall directly into Kerbin. Phew.

[Pokletu]

I had only just unlocked the SC-9000 Science Jr, and sent Bob up with it and 2 goo containers, hoping to land on the Mun with it. I realized on Munar orbit that if I went for the landing, he'd be stuck there, so I stayed in high orbit; but still had lotsa dV.

For the first time, I burned for Minmus, after finding a surpisingly cheap solution; and was reveling in all the science he'd be bringing home. On the return trip, I was distracted by RL right at the node, and wasn't as efficient as I could've been, and ended up with a peri at 69,000m, but my apo being near Mun, as I recall, when I ran outa gas. I used all my RCS to bring down my apo, then had nothing... I was stuck between waiting for the atmosphere to slow him down enough, or just reloading; and loosing all that precious science. On one of the peri's, Bill popped his nosetip parachute, hoping that would be enough to keep him in atmo. The lid didn't so much as pop off. Ultimately, that wait for drag had brought his peri's down into the 50k range.

Before that point, I think he was only out there about 9 days or so. After waiting 111 days, fast forwarding through high altitudes, I had committed too much to lose the save.

I built another rocket, without the lander stuff, and with my new Rockomax solid boosters, put my best guy, Jeb, in, and sent him up to PUSH him into the atmosphere. I haven't unlocked any docking stuff, the claw, or anything.

At the Apoapsis, finally rendezvoused, with just drops of fuel for the main engine, electric juice almost gone, Jebadiah Kerman oriented himself so that Bill's craft and the retrograde vector were in-line, using RCS, in order to conserve electric for torque, and made the burn. Of course he wasn't able to stay in line with Bill's craft, and crashed through; but all that remained was that his whole mission's hope; that nudge, was enough to knock 'em home. Leaving that to hope, Jeb reluctantly prepared for reentry himself. He landed, looking to the sky behind him; his craft recovering some scant 3 science, for any trace of Bill.

The nudge was enough. Bill's first parachute held through reentry; and was joined in timely manner by the other 2, to be recovered, after almost a year in space without food, with Science Jr and the GooPods, and over 100 science for Kerbalkind.

[Sirrobert]

Very nice sollution, but I AM going to have to tell you something now that will make you facepalm (sorry)

You could have send Bob on EVA, and use his jetpack to push the rocket

[Pokletu]

Damn. I'll have to maybe crunch the numbers, but that MIGHT have been easier.... And cheaper... And faster...

[0Kev]

Small tip:

If you have both RCS fuel, and a more efficient engine,

use the RCS fuel as soon as possible, to augment your normal thrust. (i.e. take off with normal engines *and* rcs H)

You gain more by using it early, thus decreasing its mass, than by lugging it along all the way. 102 units for a 10-ton lander is a LOT. In your case, it's good for another 108m/s delta-v, and the loss of its mass will boost your main fuel supply's delta-v by about 48 more. (depending on your engine isp, I have to guess your lander main engine type, but it looks like a 370 ISP engine to me.)

Difference between 1072 d-v and 1072+108+48=1228 is a LOT!

Of course, your original 1072 is plenty enough to get back home from Mun, even from a low-altitude polar crater.

P.S. Almost enough RCS thrust to hover on Mun? Have you seriously put 16 RCS on one Mun lander? Wow, no wonder you need so much RCS fuel!

Thanks, love the details! Yes, overkill on RCS. This is only my 2nd or 3rd Mun landing, and I had a long hiatus from the game. Still learning to be efficient in my designs. I think I had those to help stabilize and turn the whole vessel before it just had the lander remaining.