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Hermes Interplanetary Spacecraft (from The Martian) [DISCONTINUED]

xxhansonmaxx

By xxhansonmaxx
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_Augustus_

_Augustus_

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Hermes is a low-thrust craft, it doesn't like deep gravity wells - takes a lot of time to get out of them. I guess they would be starting from one of Lagrange points of moon. That also explains SLS.
Yep. They showed Hermes in LEO because it looks cooler and is cheaper that way.
I think the movie just plain left out the vehicles that brought all of this stuff down to the surface.
Yeah, keep in mind that this did have a budget. The fewer magic CGI spacecraft you make, the cheaper it is.
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sp1989

sp1989

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Yep. They showed Hermes in LEO because it looks cooler and is cheaper that way.

Yeah, keep in mind that this did have a budget. The fewer magic CGI spacecraft you make, the cheaper it is.

Even in the book the Hermes Andy Weir mentions the Hermes is big and is parked in LEO also with the bomb Lewis was worried about their aerobreaking shape. Also the SLS is fine from earth the MAV would need to be huge to get back to the Hermes if it wasn't in LMO.

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njmksr

njmksr

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I tried to post to this thread while it was really early (but I got sidetracked).

Anyways, I will happily oblige if you need any kind of tester for this mod. Can't wait for release!

[EDIT] Nevermind, I found my post. I feel really stupid now.

Still can't wait for release.

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sashan

sashan

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Even in the book the Hermes Andy Weir mentions the Hermes is big and is parked in LEO

Well, even the book is not without goofs. For example, Andy got his calculations wrong in a moment where Mark is making water. He forgot to take different densities and molecular masses of oxygen and hydrogen into account. It changes all numbers by the order of 150%, IIRC.

It would take a few months only to get out of LEO with that much thrust. Starting at lagrange point or at least high orbit is the only option I guess.

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_Augustus_

_Augustus_

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Well, even the book is not without goofs. For example, Andy got his calculations wrong in a moment where Mark is making water. He forgot to take different densities and molecular masses of oxygen and hydrogen into account. It changes all numbers by the order of 150%, IIRC.

It would take a few months only to get out of LEO with that much thrust. Starting at lagrange point or at least high orbit is the only option I guess.

Yep. It does have flaws, and Andy Weir admits it in interviews.
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sp1989

sp1989

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Well, even the book is not without goofs. For example, Andy got his calculations wrong in a moment where Mark is making water. He forgot to take different densities and molecular masses of oxygen and hydrogen into account. It changes all numbers by the order of 150%, IIRC.

It would take a few months only to get out of LEO with that much thrust. Starting at lagrange point or at least high orbit is the only option I guess.

But what about from Mars orbit? I think either way it would take large amounts of time. So to save resources staying in LEO would be the most cost efficient. Launch several SLS to refuel and resupply the Hermes would be insanely expensive. Plus building the Hermes which I suppose could have been done in LEO and then pushed out to a Lagrange point but if it was built that far out would be unjustifiably expensive. I think all the money should go to NASA lol but realistically I'm just saying a project like that would be prohibitively expensive. So I think if we are cutting cost Hermes in LEO would be cheaper in terms of ressuplying and crewing at the cost of time to the crew escaping LEO at a snails pace. Again the issue is similar when the get to Mars. They aren't going to be to high of orbit at Mars because the higher they are the larger the MAV needs to be. So LMO would be optimal and could take a really long time to escape as well.

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sashan

sashan

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Yes, you're rignt, it could be built in LEO and then slowly get to Lagrange point on itself. Crew would then get there on Orion with ICPS. I'm just saying it would just be unfeasible to do that with crew - it would increase flight time by 50% at least. It can be brought to low orbit then automatically, to ease refueling and repairs (which I guess would require few manned expeditions).

As for Mars - the solution is simple. Stay high. Intercept of MAV, for example, was done in high Mars orbit:

GPQhPoV.png

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sp1989

sp1989

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Yes, you're rignt, it could be built in LEO and then slowly get to Lagrange point on itself. Crew would then get there on Orion with ICPS. I'm just saying it would just be unfeasible to do that with crew - it would increase flight time by 50% at least. It can be brought to low orbit then automatically, to ease refueling and repairs (which I guess would require few manned expeditions).

As for Mars - the solution is simple. Stay high. Intercept of MAV, for example, was done in high Mars orbit:

http://i.imgur.com/GPQhPoV.png

That was for Watneys escape. They couldn't slow down to get into Mars Orbit. They flew by and caught him, and the MAV needed to be heavily modified to get into a higher orbit and to match velocities. I think we are having three simultaneous conversations. Let me be clear I don't disagree with you about what would be better in real life I disagree with you about the feasibility of that infrastructure in the book and movie. Furthermore in real life I can't picture the program functioning like that. I mean we are talking about a little over a dozen SLS launches per Ares mission including one that would just have the crew? Im sorry that is prohibitively expensive. Yes it would take a very very long time to leave earths gravity like that in real life but NASA will easily trade time for money. Honestly that is better because it allows resources to go towards other things. Just to be clear I am talking about the feasibility of that idea both in the martian book/movie world and in real life.

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sashan

sashan

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That-yes, but for usual mission it should be similar I guess.

What I am tapking about:

1. Hermes arrives from Mars, ges to high orbit on Lagrange point.

2. Orion docks with Hermes there, astronauts go home in the capsule.

3. Hermes is brought into LEO by remote. That may takes weeks or months.

4. Hermes is refueled and overhauled in LEO.

5. Hermes returns to Lagrange point or high orbit by remote, maybe catches one small probe to top up the fuel (described in book).

6. Orion brings crew to Hermes.

7. Hermes departs.

The point is to avoid astronaut spending weeks on Hermes as Hermes climbs out of Earth gravity well.

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sp1989

sp1989

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That-yes, but for usual mission it should be similar I guess.

What I am tapking about:

1. Hermes arrives from Mars, ges to high orbit on Lagrange point.

2. Orion docks with Hermes there, astronauts go home in the capsule.

3. Hermes is brought into LEO by remote. That may takes weeks or months.

4. Hermes is refueled and overhauled in LEO.

5. Hermes returns to Lagrange point or high orbit by remote, maybe catches one small probe to top up the fuel (described in book).

6. Orion brings crew to Hermes.

7. Hermes departs.

The point is to avoid astronaut spending weeks on Hermes as Hermes climbs out of Earth gravity well.

That works but I sorry I don't like it. Why not do something then the likes of the constellation program? Why build the Hermes of you are only going to use it half of the trip. Honestly a crew could not last no matter how well trained in a capsule from Mars to earth. The only point of having something as large as the Hermes would be for efficency and the comfort for the crew. Again time really isn't a problem there is nothing wrong with being slow. If you wanted to get to Mars and back fast why not just huge chemical rockets?

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benjee10

benjee10

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That works but I sorry I don't like it. Why not do something then the likes of the constellation program? Why build the Hermes of you are only going to use it half of the trip. Honestly a crew could not last no matter how well trained in a capsule from Mars to earth. The only point of having something as large as the Hermes would be for efficency and the comfort for the crew. Again time really isn't a problem there is nothing wrong with being slow. If you wanted to get to Mars and back fast why not just huge chemical rockets?

I think you have misinterpreted this. The crew takes Orion up to Hermes when it reaches a Lagrange point and depart from Hermes when it returns to that Lagrange point at the end of the trip back from Mars. They don't spend weeks or months in a capsule. Just a few days. It means they don't have to be on Hermes as it slowly spirals up to L1 so they save supplies for the important trip to Mars and back.

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sashan

sashan

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I think you have misinterpreted this. The crew takes Orion up to Hermes when it reaches a Lagrange point and depart from Hermes when it returns to that Lagrange point at the end of the trip back from Mars. They don't spend weeks or months in a capsule. Just a few days. It means they don't have to be on Hermes as it slowly spirals up to L1 so they save supplies for the important trip to Mars and back.

Exactly. Going to Lagrange point will take only few days in Orion, which is almost like Apollo flight to Moon. Going there by Hermes, uhm, would take a lot. It took SMART-1 probe a year to get to L1, tho it had 1/10th of Hermes' TWR.

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sp1989

sp1989

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I think you have misinterpreted this. The crew takes Orion up to Hermes when it reaches a Lagrange point and depart from Hermes when it returns to that Lagrange point at the end of the trip back from Mars. They don't spend weeks or months in a capsule. Just a few days. It means they don't have to be on Hermes as it slowly spirals up to L1 so they save supplies for the important trip to Mars and back.

OHHHHHHHHHH That isn't that bad at all! Ok Ok I get it now.

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davidy12

davidy12

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I don't understand why would they want to go to Lagrange point 1 (PS: Where is that? I assume it's in a high earth orbit). They could just send a Falcon 9 with Dragon V2/SLS Block I with Orion as a crew shuttle to LEO to rendezvous with the Hermes.

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xxhansonmaxx

xxhansonmaxx

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I don't understand why would they want to go to Lagrange point 1 (PS: Where is that? I assume it's in a high earth orbit). They could just send a Falcon 9 with Dragon V2/SLS Block I with Orion as a crew shuttle to LEO to rendezvous with the Hermes.

So that it doesn't need to go into Earth orbit

5gVihMX.png

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Luxord52

Luxord52

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It stays harbored in LEO so that they have easier access to modify, repair, and overhaul the Hermes while it's there, before they move it to Lagrange 1 and send a probe to refuel it, so that it is at one of the easiest points to escape Earth orbit, while still having full fuel. It's an efficiency thing, one that isn't demonstrable in Kerbal due to the fact that the physics system we use doesn't simulate Lagrange points. Basically, they do it so that they can save some fuel in case of emergencies on the trip, and the crew hops up after it's done moving to L1 over the course of a couple weeks. This then allows them to escape Earth gravity with minimum dV usage.

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