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Stuck on minmus


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Hello, I happen to be in a bad situation: stranded on minus with extremly low amount of fuel, very limited tech tree and Bob on board. (I am playing sience mode.) Do you have any ideas to help me get Bob back to Kerbin??imw=5000&imh=5000&ima=fit&impolicy=Lett?imw=5000&imh=5000&ima=fit&impolicy=Lett

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Bob may actually be able to get to Minmus orbit with just his EVA pack.  You could send a rescue craft that would only need to get to Minmus orbit and rendevous.  Wouldn't need to land.  Just make sure Bob removes the science from all the experiments before jumping to orbit.  Your rescue craft wouldn't need the landing gear or the science, so should have plenty of dV available.

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Mk2 pod can survive re-entry from Minmus with a 1.25m heat shield, just use the translate tool to pull it out of the pod when you attach it.  It can even survive with no heat shield, although it does get a little toastier.

While it looks silly, you can still send an Mk2 pod up on a 1.25 meter stack.

screenshot34.png\

 

Also, a couple side notes for missions like this, since you ran so low on dV.

There's two things you can do on a craft like that (assuming you didn't already) that aren't very obvious.

  • That pod has some Monopropellent in it.  If you're not using any RCS, then you don't need it!  Empty it out in the VAB.  Less weight = moar dV.
  • Similar thing applies to your heat shield.  They're ablative, so the less ablator they have, the less they weigh.  You could probably knock it down from 200 to 40 or 60 in the VAB for even more weight savings.

 

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a probe could definitely get there I think. If you have the communotron 16, that has the range to get a signal to Minmus if you have tracking stations tiers 2 or 3 which you have as you're playing science mode

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Thanks a lot for help to both of you. I'm just gonna practise randezvous in the tutorials menu and then go for rescue, with this knowlege it doesn't look like that big of a challenge. I really appreciate your help.

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Take the same design, but replace the Science Jr module with an FL-T200 fuel tank and stick a probe core (OKTO would do, but don't use a Stayputnik) between the pod and the parachute with a 16S antenna on the back of the pod, then remove most of the ablator- 40 should be enough- and launch it uncrewed. Fly to Minmus, capture into orbit, then get Bob to grab the science data from the lander on the surface and then jump and jetpack to orbit. Use the new rocket to get close to Bob (within 1km would do) and then use the remaining fuel in Bob's jetpack to fly in and board the pod. Return to Kerbin, recover Bob and science, profit!

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7 minutes ago, Mustant said:

The rescue rocket has got 3244m/s of delta V, is that enough?

In Kerbin orbit?  That will take you to Minmus and back several times.  On the launchpad?  Add a launch booster to get it into orbit.

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24 minutes ago, Zhetaan said:

In Kerbin orbit?  That will take you to Minmus and back several times.  On the launchpad?  Add a launch booster to get it into orbit.

Launch booster? That is another way to say srb am I right?

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14 minutes ago, Mustant said:

Launch booster? That is another way to say srb am I right?

Not specifically.

If the total craft you have in the VAB is showing 3244 m/s, that's not going to be enough to get to Minmus from the pad.  What Zhetaan is saying is you need to add another stage under what you have to get it into Kerbin orbit first.

Another thing to consider when checking the dV in the VAB is whether or not you're looking at atmosphere dV or vacuum.  Some engines are somewhat close.  But if you're looking at a stage with, say, a Terrier, it's going to be _vastly_ different as the Terrier is a vacuum optimized engine.  Its performance in thick air is terrible.

Take this very basic craft I tossed together.  At sea level the dV is 667.

terrieratmo.png

 

 

But in the vacuum of space, it's 2709.  Much higher.

terriervac.png

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That's probably going to be fine.

It looks like you have a terrier like my example above.  If you switch the dV reading to vacuum, you'll see the dV of your upper stage with the capsule shoot up.

You also might want to fire your core engine at launch and just leave the throttle down so you have some real pitch and yaw authority.  Would make doing your gravity turn easier.

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26 minutes ago, Geonovast said:

That's probably going to be fine.

It looks like you have a terrier like my example above.  If you switch the dV reading to vacuum, you'll see the dV of your upper stage with the capsule shoot up.

You also might want to fire your core engine at launch and just leave the throttle down so you have some real pitch and yaw authority.  Would make doing your gravity turn easier.

Yes, I agree with the core engine thing,  and I hope Bob's got enough fuel in his backpack.

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On 5/5/2022 at 12:51 PM, Geonovast said:

Mk2 pod can survive re-entry from Minmus with a 1.25m heat shield, just use the translate tool to pull it out of the pod when you attach it

One can typically also reduce the amount of ablator to lighten the heat shield.  A full value is rarely required for a typical reentry on Kerbin

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19 hours ago, Mustant said:

But you know, at this point I don`t have an Idea on how to get another stage on this:

[Image]

I see a whole-vessel delta-V of nearly 7,000 m/s and a thrust-to-weight ratio of 2.3.  You're fine.  Actually, at this point, I'll caution you that that is a very energetic lifter and you may find that, after launch, you have a hard time turning it in atmosphere without ripping pieces off if you're too aggressive with your pitch control.  If that happens, then the solution is to use the thrust limiters on the SRBs.  You should be able to turn down the thrust to, oh, 67% or so.  That will drop your launchpad thrust-to-weight to a respectable 1.5-ish which will keep your rocket flying upward but with less unplanned disassembly.

The other issue that might become a problem is staging away the SRBs when they burn out.  They can have a tendency to strike your core after you detach them.  I usually prefer pairs over quads for this reason, but don't be afraid to use Sepratrons if you need them.

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1 hour ago, Zhetaan said:

I see a whole-vessel delta-V of nearly 7,000 m/s and a thrust-to-weight ratio of 2.3.  You're fine.  Actually, at this point, I'll caution you that that is a very energetic lifter and you may find that, after launch, you have a hard time turning it in atmosphere without ripping pieces off if you're too aggressive with your pitch control.  If that happens, then the solution is to use the thrust limiters on the SRBs.  You should be able to turn down the thrust to, oh, 67% or so.  That will drop your launchpad thrust-to-weight to a respectable 1.5-ish which will keep your rocket flying upward but with less unplanned disassembly.

The other issue that might become a problem is staging away the SRBs when they burn out.  They can have a tendency to strike your core after you detach them.  I usually prefer pairs over quads for this reason, but don't be afraid to use Sepratrons if you need them.

The disassembly problem was not a problem, the craft didn`t do that and the srb disconection was fine- they hit each other, but at that point the rest of the rocket was above them.

By the way I am almost finished with the rescue just need to return to Kerbin.?imw=5000&imh=5000&ima=fit&impolicy=Lett

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A bit of advice on that re-entry.

I'm assuming it was fine because the stage you ejected was massive enough to fall faster than your pod.

However this is a very easy way to get yourself killed on re-entry.  That dropped bit could suddenly want to slow down faster than you, and run full-bore into your heatshield, likely exploding everything.

A way to avoid this is when you're close to re-entering (say 80-100km), point your craft in a direction fairly off prograde/retrograde, stage, then turn back to retrograde.  I tend to point it a little off normal/antinormal  :normal:/:antinormal: and then kick the extra bits away.  That way if it passes you or falls behind it's very unlikely to smack you.

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