Mid-course Interplanetary Abort

[NFunky]

Hey all,

So I'm playing an RSS install, but this should apply to Kerbin-Duna as much as it does to Earth-Mars.  I've got a manned mission on its way to Mars, and about half of the way there, several coronal mass ejections blasted my crew (Kerbalism) and they are now suffering serious radiation poisoning.  I need to abort the Mars trip and get them back to Earth as soon as possible.

As I said, I'm about half the way to Mars, so the the Earth is already pulling ahead of both my spacecraft and Mars in its orbit.  My ship has about 5500 m/s dV, but I'll need about 1000 of that to capture at Earth (gently aerobraking my rest of the way to LEO).

My questions are, is it possible to even perform a mid-course abort with this kind of dV?  If so, could you help me understand when and how to burn to get home as fast as possible?  ~2 years will be too long for my guys to survive!

Here is a screenshot of my situation.  Sorry for the dropbox link, but I can't seem to embed images for some reason.

https://www.dropbox.com/s/uexk1qnqynumd2w/marsabort.JPG?dl=0

[Vanamonde]

I don't use mods so I can't help you with that part, but as for posting pics, what you will need to do is upload them to a hosting site such as imgur.com (it's free) and included the link they provide in your posts. 

And good luck with your mission. 

[FleshJeb]

I think they're pretty well toast--Unless you can send medical supplies to fix/delay the problem on a high dV probe. I'm not sure if that's even possible, because I've never used Kerbalism.

What I would do to find out the return viability is use MechJeb to plot an intercept with Earth, set the maneuver to now, and set the desired intercept time to their maximum survival time. That will at least let you know the required dV.

Alternately, I think you may be able to set up a Mars a slingshot now, and a maneuver at Mars periapsis that will get you back to Earth on a really hot return. I seriously doubt the viability/scheduling of this approach, and it would take a lot of fiddling.

[Gargamel]

I think the biggest question is, how much time do they actually have? 

With enough dV, you can get anywhere, as quick as you want.  But your ship has a limited budget, so there is an upper limit to the quickest you can get back to the surface. 

Whatever you do, in order to get them back ASAP, you'll end up burning most of your dV trying to intercept the Earth, and then let's hope your ship can handle some serious aerobraking.   A brachistochrone type manuever may be necessary. 

As for the pic, if you right click the image as posted in dropbox, you can link the image location, and use the insert media button here to post it:

 

 

Edited July 1, 2018 by Gargamel

[Maffif]

So that gives 2.25km/s acceleration and deceleration (leaving the reserve 1000)

There exists some specific trajectory that uses precisely that much dV to intercept earth sooner, but I don't know if MJ has the facilities for that sort of advanced transfer, or how much sooner you can make it- odds are slim here. I would either try to weather it out, or fiddle with Mechjeb 

[taniwha]

I regret to inform you that your crew had best ensure mission control knows what hit them, and then finalize their affairs. They have bought the farm.

Radiation sickness kills in hours to weeks (note: I don't know how Kerbalism treats it).A hundred days is far too long. If you were in Kerbin's system, 5km/s would be able to make a significant dent on travel time, but not in Earth's. Earth's orbital velocity is about 30km/s, Mars' about 25km/s. Your orbital velocity is always within 5km/s of circular orbital velocity at your position (otherwise, 5km/s would not be sufficient for your Mars operations).

For your next attempt, I suggest installing a storm shelter (assuming Kerbalism supports such).

Anyway, what you would need to do is to negate your radial velocity such that you're heading sunward rather than starward, then accelerate "towards" Earth. "Towards" is complicated by curvature, and it would be best to combine the two maneuvers of course. However, it will take a LOT of accelerating towards Earth to make a significant dent in the travel time.

[NFunky]

Thank you guys!  This is fascinating.  While I hate to lose this mission, this incident has made me understand yet another reason why Mars is so much harder than the Moon.

Are there any plans for manned Mars missions that include abort provisions?  I know that was a very important part of every phase of the Apollo missions, so I assume NASA (or whoever) would want as robust an abort protocol during as much of the mission as possible.

BTW, great call on MechJeb.  I don't really ever play with it, so I forget about it's powers of education sometimes.

[NFunky]

Just a heads up, unfortunately it looks like MechJeb won't plot maneuvers in a heliocentric orbit.  The vessel has to be in a planet's SOI, or the planner gets stuck at "Computing: 2%".

[Kesa]

5 hours ago, NFunky said:

Are there any plans for manned Mars missions that include abort provisions?  I know that was a very important part of every phase of the Apollo missions, so I assume NASA (or whoever) would want as robust an abort protocol during as much of the mission as possible.

Problem is, such a protocol is not possible for a Mars mission. The Moon is only a few days away, the "abort protocol" was barely different than "proceed as planned". Moon landing can be cancelled because a stage malfunction would lead to the crew being stranded, but the overall time to return is barely shortened, but is not an issue because it is already short in the first place.

 

In real life, I don't know if there's even any meaningful treatement to severe irradiation. The most we can do, be it down on Earth or millions of miles into deep space, is prevent it. So probably kerbalism allows crew to be automatically healed upon recovery, but realistically, the crew is already doomed, even if rapid recovery were possible. And if rapid recovery was possible, I think the abort plan shoud have been triggerd from the first or second coronal blast (evaluating their frequency and your resistance to it probably could have indicated they would not make it).

 

I think our (RL) take on this will be to test each subsystem extensively before heading to Mars, precisely because there is no abort plan. Before your second mission to Mars, I advise you to do the same, and send your Mars vessel say, on a mission over an extended period of time around the Moon, where an abort is possible. Also pointing the engines toward the Sun (assuming crew compartiment are at the other end) should reduce radiation, if kerbalism is well coded, and this strategy is what spaceX intends to do IRL.

 

As for as salvaging your current mission, well if your kerbals can attempt to go home any faster than following the mission plan, it may be worth trying. If you have a very powerfull rescue craft, you don't necessarrily have to plan for a braking plan, any Earth flyby is good and the rescue craft can do most of the work (it would need a rescue craft with as much or maybe more Dv than the Mars mission itself, but due to the length of the mission, mass can probably be save on life support and Mars playload).

Personnally, I think I would carry the mission as far as possible. The kerbals on board were aware it was a dangerous mission. If you got remote control system, the craft can be put in orbit around Mars and be used for its materials by future missions. Without remote control system, you should be able to put the craft in a resonant orbit to possibly retrieve it later, sending a small probe to hack the control system and using the fuel onboard, assuming it won't disappear.

[Gargamel]

6 hours ago, NFunky said:

Just a heads up, unfortunately it looks like MechJeb won't plot maneuvers in a heliocentric orbit.  The vessel has to be in a planet's SOI, or the planner gets stuck at "Computing: 2%".

It will, you just have to target Earth, and then do a Hohmann transfer.  A porkchop planner will only work on bodies outside the Suns SOI in this situation, and well, yeah.....   I didn't mention this before, as you didn't say MJ in the OP, but MJ is optimized for the most efficient burns, not the fastest.   The limited time planner will do this, but as mentioned, yeah.....

Create a manuever node a bit out from where you are and see if you can get anything close.  Even if you have to expend all your dV to get home, if you get an encounter close enough to aerobrake....

[NFunky]

I really appreciate the advice.  My dudes ended up dying, but only after making Mars orbit and were bravely doing research until the end.  So I got good science, and you're right, now I have a depot with hydrogen fuel, food, water, oxygen and a bit of hypergolic RCS fuel.  Also, I can dock my next mission to it and use it for extra living space while waiting for the return window.

Thanks again!

[Gargamel]

6 hours ago, NFunky said:

I really appreciate the advice.  My dudes ended up dying, but only after making Mars orbit and were bravely doing research until the end.  So I got good science, and you're right, now I have a depot with hydrogen fuel, food, water, oxygen and a bit of hypergolic RCS fuel.  Also, I can dock my next mission to it and use it for extra living space while waiting for the return window.

Thanks again!

Hmmm.... Cool, I think.   But my first concern was "what about the bodies?"    Wasn't it in 2010 the one guy starts freaking out over the possible smell? 

[Daniel Prates]

On 7/1/2018 at 11:11 AM, NFunky said:

Thank you guys!  This is fascinating.  While I hate to lose this mission, this incident has made me understand yet another reason why Mars is so much harder than the Moon.

There is a great video by "curious droid" about this:

https://youtu.be/IyUwSJ5pXS0