OFMM General Discussions Archive

[Arrowstar]

We can also reduce the deceleration needed to do an aerocapture if we do it in multiple steps. ie: Aerobrake into a high elliptical orbit-> then into a less eccentric orbit-> continue process until desired ApA is attained-> circularize.

Sure. You would never attempt to aerobrake in the final desired orbit in one pass. The amount of kinetic energy you'd need to dissipate over such a short period of time would yield insane heating rates...

 

[Pablo49]

We could use that Hohmann (it's a verb now, btw) idea but send unmanned cargo to LMO before we send crew. Launch the storage modules and such over a couple trips, then send the hab modules last with the astronauts in them.

 

[Bj]

I think aerobreaking the stack would be a mistake. A stack simply is not intended to take that kind of stress. Heatshields or not, the sheer stress of plunging that thing into the atmosphere would rip it apart. It is afterall held together mostly with airlocks and other assorted docking ports. The sheer size of the heatshield needed (even if it is inflatable) is space and weight that could be better used elsewhere or left behind altogether.

My sentiments exactly. Expecially with the solar panels out like that, more like huge sails.

Pablo (or anyone else), since you have all the modules already built, can you give a estimate of the weight of each individual module there? Perhaps all we need is a little more fuel and/or second engine.

---------- Post added at 08:23 PM ---------- Previous post was at 08:21 PM ----------

We could use that Hohmann (it's a verb now, btw) idea but send unmanned cargo to LMO before we send crew. Launch the storage modules and such over a couple trips, then send the hab modules last with the astronauts in them.

I figured the storage modules would be for food, water, O2... :thumbup:

 

[Pablo49]

My sentiments exactly. Especially with the solar panels out like that, more like huge sails.

This is the MSS in Orbital configuration. It could always be rearranged to a stack configuration and then rearranged one into LMO. Either way, I still have my doubts about Aerobraking.

Pablo (or anyone else), since you have all the modules already built, can you give a estimate of the weight of each individual module there? Perhaps all we need is a little more fuel and/or second engine.

Total Mass is 244050 Kg. That's assuming empty masses for all modules besides the Service Module, and not counting the URMS (I forgot to include that in the wiki, shall edit that in).

That's more than I thought it would be. 104000kg is for the Solar panels alone; which are the most massive pieces.

EDIT: You said individual modules, whoops. I shall edit those in now (though I'll post this edit first so you know it's coming.)

Super Edit:

• Hab Core: 13900 Kg
• Hab Modules(x2): 14300 Kg
• Communications Truss: 7500 Kg
• Solaris(x2): 52000 kg
• Cupola: 11800 Kg
• Service Module: 19000 Kg
• Truss(x4): 1000 Kg
• Storage Modules(x3): 10000
• Hab Nodes(x2): 2500 Kg
• Work Modules(x2): 10000 Kg
• Truss Node: 250 Kg

 

[Bj]

Total Mass is 244050 Kg

Super Edit:

• Hab Core: 13900 Kg
• Hab Modules(x2): 14300 Kg
• Communications Truss: 7500 Kg
• Solaris(x2): 52000 kg
• Cupola: 11800 Kg
• Service Module: 19000 Kg
• Truss(x4): 1000 Kg
• Storage Modules(x3): 10000
• Hab Nodes(x2): 2500 Kg
• Work Modules(x2): 10000 Kg
• Truss Node: 250 Kg

wow thats a lot. It looks like an external drop tank is needed, but going off the calculations above, that means half an ares load and like a 16 or so minute burn. Ill crunch numbers later but that is most definitly plausable.

 

[lennartsmit]

I just have a problem with this MSS. If we aren't aerobraking because of the strength of the docking-ports, wouldn't the acceleration of the Earth-ejection also be enough to break the ship apart? Or have we got some Unobtainium bolts?

 

[Wolfer]

The Nerva 2 has a thrust of 1,500,000N and the MSS+the Nerva without any fuel has a mass of 276,050kg. That gives us about 5.43m/s^2 of maximum acceleration, less than one g. I doubt we can keep the deceleration during aerobraking under that so we would need to reinforce the docking ports. But I still think we need to get the total mass if we aerobrake and see if we really get some benefits compared to using our engine to do the MOI.

 

[Bloodworth]

I just have a problem with this MSS. If we aren't aerobraking because of the strength of the docking-ports, wouldn't the acceleration of the Earth-ejection also be enough to break the ship apart? Or have we got some Unobtainium bolts?

We are not talking about the stress of acceleration or deceleration. What we are talking about is the windshear involved in aerobreaking. This puts very different stresses on the structure than accel/decel in a vacuum.

 

[PhantomCruiser]

How about a sacrificial ballute? If properly mounted they could take the load of aerocapture, then be detached... And it looked really cool in 2010 surrounding the Leonov.

 

[Salun]

What about we launch the LOSPS satellites to mars we launch all the vessels on a stack. Similar to the shuttle Man fuel tank. Using only a fraction of the fuel to get to Mars. Basically launching the astronauts to mars with only enough fuel to get to mars. When they arrive on orbit is a fuel tank with the fuel they need to get back.

 

[Pablo49]

Hm, that is a good idea, about the prelaunch fuel tank. We could send one of Kulch's space tankers to Mars, and dock it straight to the Nerva and transfer fuel.

 

[Bj]

We are not talking about the stress of acceleration or deceleration. What we are talking about is the windshear involved in aerobreaking. This puts very different stresses on the structure than accel/decel in a vacuum.

Exactly,

I guess 5/ms is tolerable perhaps though not (realistically) with the solar panels extended like that, maybe if they where brought in more for burns?

Anyway, next steps:

Pablo, as MSS designer, that includes the order at which these modules are launched and how they are built. It looks like being single file, these modules can be placed in their final position immediately.

Next the launch director (so far, looks like myself) will figure the vessels and pilots launching the particular modules.

 

[Salun]

Im just wondering. I understand we are calling the Project Prometheus. However. Maybe we should name the ship something more Worthy of its grand scale. No USS Enterprise please.

 

[Pablo49]

I guess 5/ms is tolerable perhaps though not (realistically) with the solar panels extended like that, maybe if they where brought in more for burns?

We could bring in the solar panels, undock them, and have them running parallel with the main stack.

Pablo, as MSS designer, that includes the order at which these modules are launched and how they are built. It looks like being single file, these modules can be placed in their final position immediately.

I have them in a row for that very reason, easier to form the stack and then switch into orbital configuration. Question: Will this be built in stack formation in LEO right away, or as a station and then switched before flying as the stack? Perhaps even a hybrid could be done, I suppose. Or is that my decision to make? Also, do I need to give you the stage configuration too? (Minus the engines for now, since I don't know how many we are using and how many droptanks etc.)

Edit: Yeah, the stack needs an epic name. Like, Pablo, perhaps. :lol:

 

[Salun]

I vote for teh stack to be named the MSS H.G Wells or the MSS Samual Clemens

Edit: That or the MSS Stephen Colbert. But for the Lose of signal system I'm naming it the Tesla Constellation.

 

[Bj]

How about a sacrificial ballute? If properly mounted they could take the load of aerocapture, then be detached... And it looked really cool in 2010 surrounding the Leonov.

Interesting, could work for higher atmospheric drag, though would it be effective at a high enough altitude before too much heating and dynamic pressure occurs?

Hm, that is a good idea, about the prelaunch fuel tank. We could send one of Kulch's space tankers to Mars, and dock it straight to the Nerva and transfer fuel.

Hmm, interesting, so we send enough fuel to Mars to send the MSS back to Earth? Last I knew, we where not planning on returning the MSS... also I believe once we get to Mar's surface, we will start manufacturing fuel...

The prelaunch fuel will be mandatory for shipping the MSS to Mars however (estimated 160,000 kg fuel)

[math]
\bigtriangleup v=(1797.38* 9.81)ln(\frac{58466+160000+42000+x}{42000+x})
[/math]

or:
dv = (1797.38* 9.81)ln((58466+160000+42000+x)/(42000+x))

x being additional payload (In this case, the MSS)

so;
[math]
10,005.15 m/s =(1797.38* 9.81)ln(\frac{58466+160000+42000+244050 }{42000+244050})
[/math]

10,005.15 - 6,120.00 = 3,885.15 m/s surplus dv

I really dont think aerobreaking is even needed, provided of course, 160000 kg of fuel, and 6km/s dv to Mars.

We could bring in the solar panels, undock them, and have them running parallel with the main stack.

I have them in a row for that very reason, easier to form the stack and then switch into orbital configuration. Question: Will this be built in stack formation in LEO right away, or as a station and then switched before flying as the stack? Perhaps even a hybrid could be done, I suppose. Or is that my decision to make? Also, do I need to give you the stage configuration too? (Minus the engines for now, since I don't know how many we are using and how many droptanks etc.)

Edit: Yeah, the stack needs an epic name. Like, Pablo, perhaps. :lol:

Yep, close in, parallel with the MSS will have to work. It could be the 'temporary' burn configuration of the MSS.

Oh and by 'stack' you mean the MSS right? Correct me if I am wrong, but isn't the MSS this structure's name? Like the ISS is the entire structures name, but it is composed up of modules that have their own names.

Something that will have to be named is the Arrow or whatever vessel that could take its place.

 

[Pablo49]

No, MSS is staying in Mars orbit. IDMS would detach and return to earth to push more loads, if need be. That would need fuel for the return trip. Fuel production wouldn't start right away, we would need to first get to the surface, set up camp, then begin production. We may need the IDMS to deliver more to Mars by the time that is ready.

Yes and no, I've always taken it as it's the Stack when traveling to Mars, and becomes MSS once in orbit. Really it doesn't matter, it's just wording.

 

[Salun]

What are the modules going to be made of?(Theoretically.) Perhaps we can save a lot of weight and subsequently fuel costs and Mission times by using a sort of UCGO inflatable station building mod. Somewhat like building a air base but instead with the stack.

 

[Wolfer]

@BJ for your fuel calculations, you also need to add the dry mass of the prelaunch fuel tank(s) to the mass ratio.

Using the nerva 2 droptank as a benchmark, we have 7.25kg of fuel/kg of structure.
So 160000kg of fuel = 22069 kg of structure. Hence the tank(s) will have a wet mass of 182069kg

If we plug that into the rocket equation:
dv=16500*ln((58466+182069+42000+244050)/(42000+22069+244050))
dv=8843m/s
Which is more than enough to go to mars with a powered MOI. There may even be enough left over fuel to send the Nerva 2 with some cargo back to Earth.

 

[Urwumpe]

1. The loads for aerobraking are, at most, lower than the loads by propulsion.
2. There are no different types of loads by situation, only static and dynamic loads.
3. The acceleration is a useless value on calculating loads. What counts is the pure raw force and the torques, that are resulting from it.
4. The CBMs of the ISS use 16 bolts with 19,600 pounds pre-load force each, once completely connected. A rock solid connection. I don't find much more data on how much punishment they really take, but it seems you can generally say, that your spacecraft module will break before the bolts of the CBM.

And sorry, I find the cargo cult science in the thread a bit annoying. I might be a bit sarcastic right now, but let me put an conservative estimate: 99% of the posts in the thread are done by people, who couldn't even land on the moon, but who think that writing more posts and wild assumptions here is better than listening to the questions, suggestions and objections of those, who have the flight experience.

Hell, I can't really understand why we suddenly got the MSS, and I am completely lost why we have many posts already discussing the name for it. Instead of serious calculations, people need to discuss the most basic form of the rocket equation, without any of the really needed extensions to it. What goes on here? If the thread is about pushing the ISS into Mars orbit, we can be done in 25 seconds, write the scenario and be done with it. Sorry, I feel the focus of landing on Mars is completely lost to making screen shots and naming contests of a spacecraft, of which we still don't know, what we expect of it. I can't believe that a week had to pass, without any progress towards Mars, but with a lot of red tape being handed around. I can already see NASA landing on Mars before we have decided if we should paint the floor grass-green or mars-red. That is *garble*, absolutely *garble*.

Especially, even considering to your advantage that most people here have no university education on manned space mission design, I still feel that we have one day of discussion for just 5 minutes of using a pocket calculator. I would prefer the other way around. See that people really put effort into comparing alternatives or calculating how the flight manifest could work out for a while, before they go posting their findings for bringing the discussion forward.

I am getting a bit frustrated here, and if people really decide to name even the toilet paper dispenser Colbert, I'll openly revolt. Colbert is a perfect name for the current state of the project. The hero of the under-performers, for a under-performing project.