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OFMM Discussions for the OFMM project.

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Old 12-09-2011, 09:33 PM   #76
Scruce
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Default Spaceplane vs. Launch Vehicle

Now, there are mainly two options in getting to Mars:

Spaceplane:

Advantages:
  • Avoids discarding expensive engines and structure (vs. expendable).
  • Avoids difficulty of retrieving the large first stage (vs. reusable multistage).
  • Avoids increased development cost of two separate vehicles (vs. multistage).
  • For a winged vehicle the center of lift moves during the atmospheric flight as well as the center of mass; and the vehicle spends longer in the atmosphere as well.

Disadvantages:
  • The weight of a reusable vehicle is almost invariably higher than an expendable that was made with the same materials, for a given payload.
  • As a rough rule of thumb, 15% of the landed weight of a vehicle needs to be aerobraking reentry shielding.
  • The R&D costs of reusable vehicle are expected to be higher, because making a vehicle reusable implies making it robust enough to survive more than one use, which adds to the testing required. Increasing robustness is most easily done by adding weight; but this reduces performance and puts further pressure on the R&D to recoup this in some other way.
  • The vehicle needs wings to take off. For reaching orbit, a 'wet wing' would often need to be used where the wing contains propellant. Around 9-12% of the vehicle takeoff weight is perhaps tied up in the wings, which in turn implies that the takeoff weight is higher and/or the payload smaller.


Launch Vehicle

Advantages:
  • A wingless launch vehicle has lower aerodynamic forces affecting the vehicle, and attitude control can be active perhaps with some fins to aid stability.
  • Boosters allow the remaining engines to be smaller, which reduces the burnout mass of later stages, and thus allows for larger payloads.
  • Launch vehicles are very often supplied with boosters, which supply high thrust early on in the flight, and normally in parallel with other engines on the vehicle.

Disadvantages:
  • The vehicles used in expendable rocket launch systems are designed to be used only once in their lifetime (i.e. they are "expended" during a single flight), and their components are not recovered for re-use after launch, adding to manufacturing cost.
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Old 12-09-2011, 09:39 PM   #77
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Eh. If we need more propellant, I can kludge together a velcro ET for either vessel. Just give me the dimensions and the general color you want it, and I'll have it in a few days at most.
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Old 12-09-2011, 10:23 PM   #78
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Quote:
Originally Posted by Pipcard View Post
 That's what I meant by OFMM-1 already having a similar purpose to the MRO.
OFMM-1 doesn't select the Martian landing sites. If we change the missions around, OFMM-3 would select the landing sites and OFMM-7 would be the "TDRS" of Mars. Actually, what is the need of a solar flare warning satellite?

Last edited by Chub777; 12-09-2011 at 10:28 PM.
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Old 12-09-2011, 10:31 PM   #79
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 Actually, what is the need of a solar flare warning satellite?
To warn the crew of solar flares so that they can get to shelter.

1. The ship has no magentic field. Solar flares will be leathal.

2. Mars has no magnetic field. Again, flares will be leathal.

By having the earliest warning possible the crew get the maximum amount of time to get to shelter.

The fastest flare recorded was 1/3rd lightspeed. That gives the crew about 35 minutes from warning to having to be in the shelter before the flare hits.
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Old 12-09-2011, 11:38 PM   #80
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Originally Posted by Chub777 View Post
 OFMM-1 doesn't select the Martian landing sites. If we change the missions around, OFMM-3 would select the landing sites and OFMM-7 would be the "TDRS" of Mars. Actually, what is the need of a solar flare warning satellite?
You said
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Originally Posted by Chub777 View Post
 Yes. We could make OFMM-3 a mission to launch a satellite similar to the MRO. Then we could pick a landing site and use OFMM-4 as a dress rehearsal on the moon.
Oh, I get it now. I thought you meant OFMM-3 selected the lunar landing site for OFMM-4 (and subsequently, I thought that OFMM-1 already served that purpose).

So what you really meant was OFMM-3 (unmanned) goes to orbit Mars and we select a landing site, then OFMM-4 (manned) lands in a similar area on the Moon. I was sort of confused by your wording.

And I feel like people are bashing on me because of the patches. Okay, I'll wait until the first mission actually starts before making them.

Last edited by Pipcard; 12-09-2011 at 11:43 PM.
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Old 12-09-2011, 11:43 PM   #81
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I've been looking over the mission list, and there were a few things I noticed:

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Originally Posted by garyw View Post
 OFMM-7 - 3 x Comms satellites to Mars - Equ orbit 60 degress apart
OFMM-8 - 3 x Comms satellites to Mars - Equ orbit 60 degress apart
I'm confused with this. Assuming we have one satellite on the Martian equator, that's one satellite at 60 degrees inc, and one at -60 degrees. We then... come back the next mission and place them at the same inclinations to spread out the coverage?

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 OFMM-22 - Excursion to Phobos for core sample retrieval (special request of the Russians)
With what ship? Would we bring a second ship to perform this mission, or would the pilot just hop in the landing ship and hope nothing goes wrong? Assuming we bring a second ship, that would cut out the Arrow as a possible ship to bring to Mars. If not... well, we do have the luxury of just reloading should we fail to get to Phobos correctly, but if we're aiming to do things at least somewhat realistic, should we really take the only lifeline on the martian surface if we leave some UMMUs in a temporary base?
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Old 12-09-2011, 11:48 PM   #82
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Originally Posted by Kveldulf View Post
 I'm confused with this. Assuming we have one satellite on the Martian equator, that's one satellite at 60 degrees inc, and one at -60 degrees. We then... come back the next mission and place them at the same inclinations to spread out the coverage?
6 satellites on aerostationary orbit. Placed at 0,60,120,180,240,300 and 360 degress lattitudes. This way you cover some 85% of the martian surface with comms and have backups. Two seperate missions launching three each in case of mishaps. Worst case scenarion is just three satellites spread 120 degress apart.

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Originally Posted by Kveldulf View Post
 With what ship? Would we bring a second ship to perform this mission, or would the pilot just hop in the landing ship and hope nothing goes wrong? Assuming we bring a second ship, that would cut out the Arrow as a possible ship to bring to Mars. If not... well, we do have the luxury of just reloading should we fail to get to Phobos correctly, but if we're aiming to do things at least somewhat realistic, should we really take the only lifeline on the martian surface if we leave some UMMUs in a temporary base?
Hence why I suggested the Cosmos in an apollo-esque scenario - no one left of the surface. Cosmos can take two DG's/XR's in case of problems with a DG no one gets left on the surface. Phobos mission would only happen if the Mars mission was done, we had time AND both ships were in good shape.

Last edited by garyw; 12-09-2011 at 11:50 PM.
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Old 12-09-2011, 11:49 PM   #83
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Quote:
Originally Posted by garyw View Post
 
OFMM-14 - Lander to Mars, target primary site

[...]

OFMM-22 - Excursion to Phobos for core sample retrieval (special request of the Russians)
Perhaps we send a spacecraft bus with two landers for each mission to save on launches, after the landers have landed, the orbiter can perform Mars reconnaissance mapping?
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Old 12-09-2011, 11:52 PM   #84
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Originally Posted by Pipcard View Post
 And I feel like people are bashing on me because of the patches. Okay, I'll wait until the first mission actually starts before making them.
Or you could wait until the final mission list goes up. You are making patches for missions that are still under review.

---------- Post added at 23:52 ---------- Previous post was at 23:51 ----------

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 Perhaps we send a spacecraft bus with two landers for each mission to save on launches, after the landers have landed, the orbiter can perform Mars reconnaissance mapping?
Why save on launches? Do you want people to miss out on the fun of going to Mars?

More could be done with fewer launches but more would be lost if that launcher fails and I wanted to give as many people as possible a crack at a mars mission.
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Old 12-09-2011, 11:59 PM   #85
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Originally Posted by garyw View Post
 Why save on launches? Do you want people to miss out on the fun of going to Mars?

More could be done with fewer launches but more would be lost if that launcher fails and I wanted to give as many people as possible a crack at a mars mission.
Well, you can always let the first person land the first Mars lander, then hand it over to the second person to do the Phobos sample return mission, then the third would do the Mars mapping?

But I do understand on the fact that if a launch fails, it's all gone.
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Old 12-09-2011, 11:59 PM   #86
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Quote:
Originally Posted by garyw View Post
 6 satellites on aerostationary orbit. Placed at 0,60,120,180,240,300 and 360 degress lattitudes.
I think you meant longitudes.
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Old 12-10-2011, 12:05 AM   #87
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Originally Posted by Pipcard View Post
 I think you meant longitudes.
Yup I did. Just checking to see if people were awake. honest.

---------- Post added at 00:05 ---------- Previous post was at 00:04 ----------

Quote:
Originally Posted by Scruce View Post
 Well, you can always let the first person land the first Mars lander, then hand it over to the second person to do the Phobos sample return mission, then the third would do the Mars mapping?

But I do understand on the fact that if a launch fails, it's all gone.
If people want to do that then it's cool with me but I also want to include errors so if someone makes a mistake and the rocket misses mars then it misses mars and we lose stuff. Keeps it interesting.
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Old 12-10-2011, 12:07 AM   #88
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Originally Posted by Pipcard View Post
 I think you meant longitudes.
Garyw's statement could easily have a double meaning. But the orbit's wouldn't be "Areostationary". Yet... stable enough for a couple of years. The moon here on Earth, messes up much more our GEO sattelites, than the tiny rocks that orbit Mars.
That said, good catch Pipcard.
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Old 12-10-2011, 12:07 AM   #89
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Quote:
Originally Posted by garyw View Post
 I've not looked at the James cook at all.
But it actually comes with a gravity wheel, so when people land on Mars, their bones won't be too weak.

Quote:
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 If people want to do that then it's cool with me but I also want to include errors so if someone makes a mistake and the rocket misses mars then it misses mars and we lose stuff. Keeps it interesting.
And why would a mission fail? With quicksaves, you can only fail on purpose. Don't tell me I have to do the entire mission in one go.

Last edited by Pipcard; 12-10-2011 at 12:14 AM.
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Old 12-10-2011, 12:12 AM   #90
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 But it actually comes with a gravity wheel, so when people land on Mars, their bones won't be too weak.
Fair point - James cook in place of the cosmos.

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 And why would a mission fail? With quicksaves, you can only fail on purpose. Don't tell me I have to do the entire mission in one go.
No you don't have to do the mission in one go but if something goes with a launch I think it would be more interesting if OFMM rolled with that failure. For example, if a mission to Mars fails because the burn is done incorrectly don't you think it would be more interesting to work with it rather than quit and reload?
Don't you think that every mission going perfectly is.. well, a little dull?
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