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Brainlord Mesomorph

How a build a 22,000 m/s dV spaceship?

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I stupidly took a rescue contract with looking where it was. The guy is in solar orbit almost in the corona!

Its going to take a 3500 m/s burn just to get my Pe to match, then a 6km/s burn to circularize, then rendezvous then a another 10km/s + to get to Kirbin and another km/s to LKO.

My first attempts came out to 6 km/s and 10 km/s, I was wondering if adding SRBs to the mix might help.

Any ideas?

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Set up a mining operation on Moho, and it would be a lot easier... but if he really is almost in the corona, it sounds like an impossible mission without heat limits turned off... reentry heating would be minor compared to that...

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Same goes for refuelling on a low gravity planet/moon.

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1 minute ago, Brainlord Mesomorph said:

I stupidly took a rescue contract with looking where it was. The guy is in solar orbit almost in the corona!

Its going to take a 3500 m/s burn just to get my Pe to match, then a 6km/s burn to circularize, then rendezvous then a another 10km/s + to get to Kirbin and another km/s to LKO.

My first attempts came out to 6 km/s and 10 km/s, I was wondering if adding SRBs to the mix might help.

Any ideas?

MOAR boosters

Seriously though, don't try to do it all I a single craft.  Break it down.  Save 900 ms dv by bringing down refueling the main craft when it is eliptically orbiting between kerbin and the SOI.  

Have a refueling craft at Moho or eve might help too.

Peace.

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A mining setup on Gilly is nice here, because the Gilly - Eve assist - Moho transfer is not nearly as bad as Kerbin - Moho.

My single-LVN-core deep space relays with six radial drop tanks have around 15km/s deltaV, and if you were to drain them instead of dropping them on the way to Gilly, refuel, and then drop them as you do the rescue, you'd definitely have enough to get back to Gilly and refuel the remaining core. Make sure your relay network is comprehensive -- that close to Kerbol, coverage is terrible.

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You may not need so much dV coming back because you could skip the circulation at Kerbin and go straight for re-entry. Do-able I think with a small, light craft. 

Overall though it should be do-able. I've done it before when going for a low solar explore. Might depend though just how low you need to go, it can get a tad warm down there. You might want to try setting the orbit of a test craft using the Alt-F12 cheat menu first. 

You will need a very light craft and a few ion stages. 

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6 minutes ago, Foxster said:

You may not need so much dV coming back because you could skip the circulation at Kerbin and go straight for re-entry. Do-able I think with a small, light craft. 

Overall though it should be do-able. I've done it before when going for a low solar explore. Might depend though just how low you need to go, it can get a tad warm down there. You might want to try setting the orbit of a test craft using the Alt-F12 cheat menu first. 

You will need a very light craft and a few ion stages. 

I did some tests about 18 months ago, to find out what kind of speed I could safely re-enter Kerbin's atmosphere at. I managed to make it down safely when I hit the upper atmosphere at 6700m/s.

However I don't know if atmospheric heating and part tolerances has been significantly altered since version 1.13.

I've had more powerful vehicles in the past, about 30km/s if memory serves, but that was in the pre-nerfed ion days.

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I put together something roughly like what you wanted. According to KER It had enough fuel that from the 91km orbit orbit I put it in, it should be good for 18km/s from there.

I took it for a little test drive and took a few snaps along the way.

LoRxKuI.png

Q21EPvp.png

EQPRLhS.png

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aYfXGQW.png

By the time it finished burning I'd reversed my orbit and had pushed the AP out almost as far as Eeloo.

If you really wanted to get up to 22km/s, then adding a another xenon tank to the single one that this has would probably take it over the line.

Edited by purpleivan
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Using ions for manned missions is usually a huge pain, but this mission is pretty much begging for it. That close to the sun, you can power multiple ions with fixed panels, or one pair of 1x6. Most of the deltaV will be spent close to the sun. Hope you got paid for this contract -- ions are expensive.

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Wow thanks for all the ideas guys.

I just spent a pleasant hour in the VAB trying to do this by multistaging atomics.

Working  backwards from reentry through the mission I was able to design a 5 stage nuclear asparagus staged thing that could do the last 80% of the mission. But that was over 200 tons, and $200,000 and I still needed a first stage to carry that 4 km/s. AND then I need to put THAT in orbit!  

LOL! 

Fuel Bases on Gilly and/or Moho it is!

I'm already planning a Gilly Fuel base mission, I have a window in 100 days. I just looked and there is a Eve>Moho window 150 days after they arrive. I could extend that mission to build a base on Moho, and once the tug is fueled in the orbit of Moho... I'll have to see

 

1 hour ago, purpleivan said:

I put together something roughly like what you wanted. According to KER It had enough fuel that from the 91km orbit orbit I put it in, it should be good for 18km/s from there.

 wow how much does that cost?  (I don't have xenon yet)

Edited by Brainlord Mesomorph

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Are you stock only?

I made a vessel a while ago which had over 60,000 m/sec of dV.  It was a two launch ship, with a docking in LKO.  

Look for the Retro Solar Challenge to see a number of ships with the required dV

Edited by linuxgurugamer
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Launching the actual rescue craft empty as a payload into LKO and then refuelling it is often a lot easier than trying to launch the whole thing in one go, especially when that much dV is needed.

Let us know the name of the Kerbal you're rescuing and keep us updated :) 

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This question about how to play the game has been moved to Gameplay Questions. 

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For reference, this is the Retro Solar Rescue thread:

While you can definitely brute-force it with ions and nukes, if time permits, you might also try a Jool slingshot/Oberth maneuver to flip your orbit.

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You can, in principle, do this with chemical rockets, but it'd be a beast and a half. You need a mass ratio on the order of 900. My sketched out attempt ran out of room in the VAB :v

 

 

Edited by foamyesque

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I'd go for a Jool double slingshot (Jool slingshot with additional Laythe or Tylo pass) or straight bi-elliptic transfer.  I once tried to do an unmanned Laythe flyby, and ended up solar retrograde accidentally...

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10 hours ago, KerikBalm said:

but if he really is almost in the corona, it sounds like an impossible mission without heat limits turned off... reentry heating would be minor compared to that...

I feel the need to re-emphasize KerikBalm's comment here. I can think of few things more frustrating than putting the whole mission together, successfully rendezvousing, only to have your lost kerbal poof from heat the instant they bail out to transfer vessels. Claw retrieval and inflatable heat shields make for a much larger craft, but may be required.

Edited by Jarin
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8 hours ago, Brainlord Mesomorph said:

wow how much does that cost?  (I don't have xenon yet)

Ahhh... don't remember, but it was a lot. It was in sandbox so cost was not an issue.

If cost is a factor, but you have ISRU, then it sounds like launching something like my nuke upper stages, but mostly empty, to Gilly and fuelling it up there is going to be a better option.

Edited by purpleivan

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16 hours ago, Brainlord Mesomorph said:

How a build a 22,000 m/s dV spaceship?

Mathematically and conceptually, the answer to this question is far simpler than you think it is.

It's the practical application that gets tricky for a variety of reasons, with the main reason being complexity. You absolutely need multiple stages unless you use ion drives, and you have stated that those are not available to you. And even with ion drives, you'd probably employ at least one staging operation and/or drop tanks to make it more usable. It's easy to screw up the balance of your individual stages, resulting in a situation where you don't get the numbers you expect from a relatively large investment of resources.

Recommendation 1: accept low TWR. In order to keep this project from going off the charts in every conceivable manner, you need to run at fairly high mass fractions - approaching 4 for LFO, or 3.5 for LF-nuclear. And engines are dead mass. Especially nuclear engines. Flying with low TWR is tedious, but apart from player comfort there are no reasons to pack more than one engine that cannot also be mitigated through skillful flying.

Recommendation 2: balance your stages, according to the rule of thumb mentioned in the link above. Make sure they all have similar mass fractions, and none is overloaded. You might think that making a stage for each leg of your journey is the way to go - one for the departure burn, one for circularizing in low solar orbit, and so on and so forth. But because each leg has different dV requirements, that often ends with seriously unbalanced stages. Which is not as much of a problem for smaller missions, but definitely is one for missions in this size class. And remember: stages are balanced by mass fractions, not dV capacity!

Recommendation 3: consider orbital assembly. Making this a monolithic launch is asking for trouble. It can be done, no question, but it could definitely be done more easily by splitting the load. The simplest method of orbital assembly is simply launching the spacecraft with empty tanks, and then fuelling it in orbit - either from Kerbin, or from a Minmus mining base. This trick alone will reduce your required lifter payload capacity by 70% or more, due to the high mass fractions you'll use. Of course, it comes with the downside of having extra work in fuelling it up in orbit, but that may be preferrable to struggling for hours in the VAB.

Following this advice, one chemical and two nuclear stages should do it, starting from Kerbin orbit. Launch sold separately. :wink: 

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@Streetwind thank you for the information behind that link. The "10 * ISP give or take a bit" rule of thumb for staging is brilliant -- simple yet effective. I will be paying attention to that from now on.

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17 hours ago, linuxgurugamer said:

Are you stock only?

I made a vessel a while ago which had over 60,000 m/sec of dV.  It was a two launch ship, with a docking in LKO.  

Look for the Retro Solar Challenge to see a number of ships with the required dV

Ah yes... Do you have pictures of this? I'd like very much to see it.
Fire

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7 hours ago, Streetwind said:

Flying with low TWR is tedious, but apart from player comfort there are no reasons to pack more than one engine that cannot also be mitigated through skillful flying.

Sorry, cannot resist the urge to nitpick...

It is totally possible to be too miserly with the engines. When leaving Kerbin, I'd recommend a TWR of no less than 0.15 (preferably 0.2) -- below that, the losses from a long-duration burn will be greater than the straightforward dV loss from adding more engine mass.

In a solar orbit, you can probably afford much less; actually, you can afford to stage most engines and continue on miniscule thrust once you've accumulated a few hundred m/s of excess escape velocity and are far enough from Kerbin to be flying away on a virtually straight line. The 0.15g rule is really only about Kerbin departure, for most of this particular mission you can make do with less. So yeah, I'm nitpicking.

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10 minutes ago, luizopiloto said:

22000m/s Δv... does it have to be manned? if not... IONs... :P

This.   Ions are perfect for this kind of mission.   In such low orbit,  a couple regular solar panels should supply all the electricity you need.  And TWR does not really matter in solar orbit.   

You can make a very nice rescue craft with an Mk 1 pods,  three ions,  and three large xenon tanks, asparagus staged.

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1 hour ago, Laie said:

Sorry, cannot resist the urge to nitpick...

It is totally possible to be too miserly with the engines. When leaving Kerbin, I'd recommend a TWR of no less than 0.15 (preferably 0.2) -- below that, the losses from a long-duration burn will be greater than the straightforward dV loss from adding more engine mass.

That is why I disclaimed with "... that cannot also be mitigated through skillful flying" :wink: Periapsis kicking is a perfectly servicable, if rather tedious, way to leave Kerbin without maneuvering losses.

 

34 minutes ago, luizopiloto said:

22000m/s Δv... does it have to be manned? if not... IONs... :P

He writes further up in this thread that he doesn't have them unlocked yet.

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