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Can I slow down my orbit enough to land on Eve?


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Ok so this SE question basically says it all, but I'm re-posting here because you people probably will know more about this: http://gaming.stackexchange.com/questions/284475/can-i-slow-down-my-orbit-enough-to-land-on-eve

I've successfully gotten a craft in circular orbit around Eve about 100,000 meters up for the first time (I'm a noob). I'd like to land on Eve, however when I try to adjust my orbit into the planet, I'm going way to fast. Over 3200 m/s. 

My question is actually rather simple: Is it possible for me to slow down enough to land, and if so how can I slow down?

My resources are as follows:

 - 1 atomic rocket motor
 - 4 electric propulsion engines
 - 2 Mk2 radial parchutes and 1 top parachute
 - 2155 Xenon Gas
 - 470 liquid fuel
 - 1 poor Kerbal who might be stuck in orbit for the rest of her life

This is my craft:

4nrrv.jpg

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In order to work out what that much fuel, through those engines, can achieve we'd need to know the mass of vehicle (fully fuelled).  From that we'd calculate the deltaV; the amount it can accelerate or decelerate (which is just accelerating backwards).

As important as speed, however, is heat-management and - off the top of my head - I think you will almost certainly burn-up on entry to the atmosphere.  Should you survive that, those engines are all super-efficient but very low-thrust so would not be able to stop the fall.  Neither do you have enough parachutes or legs for Eve, it's the highest-gravity planet in KSP!  It's not quite the hardest place to land but it is definitely the hardest to take off from again.

ETA:  It's a trap!  Flee, flee for your life!

Edited by Pecan
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It'll certainly be a one way trip but you should be able to knock off a couple of thousand m/s and get down without burning up but you'd probably be better off flying that around elsewhere and using a heat shielded habitat module for future one way crew drops.

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1 hour ago, Pecan said:

As important as speed, however, is heat-management and - off the top of my head - I think you will almost certainly burn-up on entry to the atmosphere.  Should you survive that, those engines are all super-efficient but very low-thrust so would not be able to stop the fall.  Neither do you have enough parachutes or legs for Eve, it's the highest-gravity planet in KSP!  It's not quite the hardest place to land but it is definitely the hardest to take off from again.

Absolutely agree with Pecan on the burning-up part.

In my experience, the killer zone in Eve's atmosphere is around the 70-75km mark. That's where a shallow re-entry trajectory will still be at near-orbital speeds, while the atmosphere starts getting thick enough to destroy an unshielded craft instantly. To survive that unshielded, you probably need to lose about 1000m/s by the time you get there using engines, which doesn't look entirely impossible with that craft but will not be easy.

However, whatever happens you are guaranteed to lose the solar panels, so you will only have the power that's in your batteries from then on.

If you survive that, parachutes are much more effective on Eve. Your engines will all be useless in the lower atmosphere, so engine braking on landing will do nothing, but with empty tanks you might be able to land most of the ship in one piece (or several pieces). Definitely a one-way trip however you look at it...

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Aerobraking alone cannot and will not be survivable, so you need to rely on engines (or heatshields but that craft lacks them).  Ive tried many times and aerocapture/aerobrake mandates some sort of heat shield (unless you make a massive wing which has so much drag is may as well be a airbrake), and the biggest problem is when you enter into around 75% of teh atmosphere's max height where you are moving too fast and the atmo isnt quite thick enough for you to get decent braking performance out of a craft like the one you pictured.  If you really want to try it, i suggest getting just above teh atmo and gun the engines full power retrograde and dont stop using em until you are well below 40km (if you can get that far aerobraking dominates heat in most vessels).  It is really a 50-50 chance (i wouldn't do it without a revert option, nbo idea what settings you play on), worth a try if you are a gamber, but i would say that the particular craft you have is unlikely to be able to pull off a successful Eve landing nomatter how you do it because you need some decent TWR to actually brake with engines so your speed drops faster then your altitude does.

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Ok, thanks to everyone. I'll give it a go and see what happens. Btw, I should've mentioned: I never intended to bring the Kerbal back on this mission. I intended to land her then send a future mission with one of the 3 man Apollo (sorry I don't know the name) capsules to bring her back. 

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What you might be able to do (if you haven't already) is to deliberately burn up the bottom part of craft on the way down. Then land just the capsule and not too much else with the three chutes. 

Edit: Just tried it with what I think is a close copy of your craft and I couldn't do it. Things just got too hot and the craft heatploded. Why not go to Gilly instead?

Edited by Foxster
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1 hour ago, Foxster said:

What you might be able to do (if you haven't already) is to deliberately burn up the bottom part of craft on the way down. Then land just the capsule and not too much else with the three chutes. 

Edit: Just tried it with what I think is a close copy of your craft and I couldn't do it. Things just got too hot and the craft heatploded. Why not go to Gilly instead?

I suppose I could try Gilly. Don't think I'll make it to eve. Thanks for the suggestion!

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2 hours ago, Foxster said:

What you might be able to do (if you haven't already) is to deliberately burn up the bottom part of craft on the way down. Then land just the capsule and not too much else with the three chutes. 

Edit: Just tried it with what I think is a close copy of your craft and I couldn't do it. Things just got too hot and the craft heatploded. Why not go to Gilly instead?

I don't have hyperedit installed in 1.1.3, but it was quite manageable in 1.1.2...

That fuel load of 470 units is actually quite crucial. Much more than that and it probably would have been impossible.

How to do it (and this might well be improved by reducing fuel load to about 400 units total, just by burning prograde and retrograde repeatedly), assuming a 100x100km orbit:

- shut down the ion engines - they'll do nothing but use your power, and you need to keep it if possible.

- pick your landing spot, and start burning about 1/3 of a hemisphere away from it

- burn hard directly retrograde

- when vertical descent (the climb rate meter next to the altimeter) shows about 50 m/s negative (the notch just before 100m/s marker), pitch up to about 25-30° above the horizon, keep burning

- when severe heating starts to show (should be still a while, well after exceeding 100m/s descent rate) return to directly retrograde and start rolling as fast as possible.

- you'll lose your solar panels quite quickly, followed shortly afterwards by the LV-N. If you manage to keep rolling, you should be able to keep one or more batteries

- land (4.3m/s touchdown, when I tried it, very manageable). Press F5 before trying to EVA (your pilot could easily die from falling).

Edited by Plusck
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If your TWR is high enough (think over 1 to start) you can burn retrograde, then burn increasingly radial to keep your descent velocity near zero.  If you set it up to begin this process just inside the atmosphere (think 80km or higher) you will be able to lose speed due to air drag while keeping your craft on something like a "forced orbit." Once you slow down to about 1800-2000 m/s you will likely be burning at about 45 degrees pitch - you can then just burn straight retrograde and heating should not be a huge issue as you will shed even more speed before you hit thick air. 

The issue is the delta-v requirement. You need 3200 m/s to cancel your orbital speed. With a starting TWR of 1 you would likely need at least 1500 m/s more to fight gravity long enough to slow down - if your TWR is say 2 you should be fine as you can stop very quickly. 

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The problem with Eve is never slowing down (well, until the final ten meters anyway), it's in not burning up. Eve has a huge gravity, which is why your orbital velocity looks so high, but it also has a massive atmosphere that can slow down even very heavy vehicles quite quickly. The problem is the thermal loading you get while that's happening. Eve's atmosphere will render your engines useless for a powered landing, but it might be possible to do a sea-level splash-down on the chutes, if you can get through the thermal interface. Unfortunately your rocket is not well-suited to that; I personally prefer landing on Eve with wings, since they make reentry a much more controllable problem.

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31 minutes ago, foamyesque said:

The problem with Eve is never slowing down (well, until the final ten meters anyway), it's in not burning up. Eve has a huge gravity, which is why your orbital velocity looks so high, but it also has a massive atmosphere that can slow down even very heavy vehicles quite quickly. The problem is the thermal loading you get while that's happening. Eve's atmosphere will render your engines useless for a powered landing, but it might be possible to do a sea-level splash-down on the chutes, if you can get through the thermal interface. Unfortunately your rocket is not well-suited to that; I personally prefer landing on Eve with wings, since they make reentry a much more controllable problem.

Yeah, next time I go to eve I'll redesign so I've got stronger engines, heat shields and some wings.

7 hours ago, MaxL_1023 said:

If your TWR is high enough (think over 1 to start) you can burn retrograde, then burn increasingly radial to keep your descent velocity near zero.  If you set it up to begin this process just inside the atmosphere (think 80km or higher) you will be able to lose speed due to air drag while keeping your craft on something like a "forced orbit." Once you slow down to about 1800-2000 m/s you will likely be burning at about 45 degrees pitch - you can then just burn straight retrograde and heating should not be a huge issue as you will shed even more speed before you hit thick air. 

The issue is the delta-v requirement. You need 3200 m/s to cancel your orbital speed. With a starting TWR of 1 you would likely need at least 1500 m/s more to fight gravity long enough to slow down - if your TWR is say 2 you should be fine as you can stop very quickly. 

 

7 hours ago, Plusck said:

I don't have hyperedit installed in 1.1.3, but it was quite manageable in 1.1.2...

That fuel load of 470 units is actually quite crucial. Much more than that and it probably would have been impossible.

How to do it (and this might well be improved by reducing fuel load to about 400 units total, just by burning prograde and retrograde repeatedly), assuming a 100x100km orbit:

- shut down the ion engines - they'll do nothing but use your power, and you need to keep it if possible.

- pick your landing spot, and start burning about 1/3 of a hemisphere away from it

- burn hard directly retrograde

- when vertical descent (the climb rate meter next to the altimeter) shows about 50 m/s negative (the notch just before 100m/s marker), pitch up to about 25-30° above the horizon, keep burning

- when severe heating starts to show (should be still a while, well after exceeding 100m/s descent rate) return to directly retrograde and start rolling as fast as possible.

- you'll lose your solar panels quite quickly, followed shortly afterwards by the LV-N. If you manage to keep rolling, you should be able to keep one or more batteries

- land (4.3m/s touchdown, when I tried it, very manageable). Press F5 before trying to EVA (your pilot could easily die from falling).

Seems like it would be possible based on what you guys said but I doubt I've got the skill to pull it off. Also, I landed on Gilly already because I gave up lol.

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