OFMM General Discussions Archive

[Alexw95]

I am against this, what ever we do, it should NEVER exceed the complexity of a XR-Vessel or AMSO, because otherwise, we would

a) need years to develop things
b) need years to teach all pilots to fly it.

Ideally, we should maybe have a common base class for all our DLL based vessels, that like for the XRs implements a lot of common stuff and allows to just adapt it to something else.

Personally, I would even prefer if the subsystem simulations focus on the ground operations and survival of the crew, and does not go to extremes with navigation or electrical power stuff.

yes for sure dgiv panel = to complex lets not go higher than amso or the stock dg panel if we are going to make somthing

 

[Izack]

yes for sure dgiv panel = to complex lets not go higher than amso or the stock dg panel if we are going to make somthing

Well, I wouldn't say the DG-IV panel is too complex, but I agree. Orbiter is complex enough for most people to handle. I for one don't want special training to fly a mission, especially if I fly more than one. Also, as Urwumpe said it adds too much complexity and time to the development process.

I'm still working on a preliminary manual, but I have a few questions/propositions:
1. The OSHV is already decided upon, but what about the primary truss and service module? Communications?
I suggest a second major vehicle, which is a combination of those three things, launched by the same vehicle (the Ares V in this case) as the OSHV, as a separate launch.
2. Launch vehicles? I can't imagine we're going to use a pile of Ares Vs for one mission. The Ares I and Space Shuttle might be helpful (see below.)
3. Crew? I was thinking an initial crew of no larger than 10, and optimally 8.


PRELIMINARY LAUNCH SCHEDULE (Rough overview):
Please tell me what you would have changed. I don't expect this will be finalised in even 10 versions.
Launch 1: Ares V - OSHV
Launch 2 - Ares V - SSCM (Service Structure and Communication Module)
Launch 3 - Ares I/Orion CTV - Expedition A (4 astronauts)
- Activation and shakedown of OSHV
- Manual rendezvous with SSCM
Launch 4 - Ares I - Mission Package 1A - Cargo/supplies needed for trip,
and the SMEV
Launch 5 - Ares V - NERVA-2 IDMS
Launch 6 - STS - Expedition B (8 astronauts - 4 transfer to OSHV)
- Mission Package 1B - Further cargo, Skycrane system

Again, please assist me with improving this.

Further requests:
Could I get any extra information from Bj or Columbia42 regarding the OSHV? Mass, dimensions, shape, anything?
Ashaman what is the mass of your refinery?

 

[Urwumpe]

Could I get any extra information from Bj or Columbia42 regarding the OSHV? Mass, dimensions, shape, anything?

I currently estimate the mass of the OSHV to be comparable to the Hab of the Mars Direct Plan - the mass it lacks for propulsion systems and heat shield, it adds as additional laboratory space. That means, about 30 tons of mass. Since we are in the beginning of the development, I even increased the mass budget of it to 40 tons for calculating the propellant demands of the Sky crane.

What needs research on my side is how much drag surfaces the Skycrane needs for which terminal velocity. This is an optimization problem: The less drag the Skycrane produces during late reentry and the less mass is allocated to such aerodynamic drag devices, the more fuel mass it needs for landing and lift-off.

I already have a nice shape in my head for the skycrane to do such a mission, but this shape adds mission mass by requiring an expendable heat shield for covering the payload, for example an IRDT like inflatable heat shield.

 

[Ashaman42]

Ashaman what is the mass of your refinery?

The rock miner comes in a packed cargo box of 1000kg and the ore mill requires 4 packed boxes of a 1000kg each.

 

[Izack]

The rock miner comes in a packed cargo box of 1000kg and the ore mill requires 4 packed boxes of a 1000kg each.

That's a lot lighter than I expected. In that case the Ares I isn't necessary. For 5 tonnes of equipment, and I'm guessing the SMEV isn't any bigger than 5 tonnes itself, Than 25.4 tonnes of carrying capacity (Ares I) is more than a little overkill...

 

[Urwumpe]

That's a lot lighter than I expected. In that case the Ares I isn't necessary. For 5 tonnes of equipment, and I'm guessing the SMEV isn't any bigger than 5 tonnes itself, Than 25.4 tonnes of carrying capacity (Ares I) is more than a little overkill...

Well, maybe we can design the SMEV and the sky crane from common parts, in that case, the SMEV might be able to become a bit heavier than the minimum solution, for sharing more parts. And if we don't use a skycrane (despite the advantages), such common engineering might still make things easier.

For the design - any suggestions for the ISP or maybe even engine types? We could maybe agree on a library of "standard" engines, that we use in the project and which are the design reference.

 

[Voyager]

Perhaps, some sort of nuclear engine after heading past Earth for about 250,000 kilometers, that would activate. It could be the prime engine idea;

 

[Urwumpe]

Perhaps, some sort of nuclear engine after heading past Earth for about 250,000 kilometers, that would activate. It could be the prime engine idea;

Please, learn flying interplanetary missions FIRST and then take part in such discussions. Real physics don't work like that, this isn't star trek here.

For getting to 250,000 km distance to Earth, almost out of Earths gravity well, you need almost as much dV as for flying from low Earth orbit to Mars directly. and for flying to 250,000 km apogee first and then to Mars, you need more total dV than for flying to Mars directly (Oberth effect).

If you would have basic experience with such flights, you would know the relations. You would know where you spend your fuel for what effect. And not do such unqualified statements.

Nuclear engines really make sense for such flights, but not if you wait for using them for the smallest velocity changes.

 

[Ashaman42]

That's a lot lighter than I expected. In that case the Ares I isn't necessary. For 5 tonnes of equipment, and I'm guessing the SMEV isn't any bigger than 5 tonnes itself, Than 25.4 tonnes of carrying capacity (Ares I) is more than a little overkill...

Well I have no idea if my numbers are at all realistic, I just picked a nice round number. Easy enough to change though as the cargo weight is set by config file.

I will check later and see what I've set the unpacked weights to as there may be a discrepancy. I didn't worry too much about weight as I regarded the miner and mill as fixed but if we might be shifting unpacked equipment around it may need looking at.

As well as setting some attachment point maybe?

As for engines I've been pottering at a cargo lander/lifter and am leaning towards a methane/Lox engine. Whilst methane and LH2 are both able to be made in situ it seems that methane is easier to store.

 

[Urwumpe]

As for engines I've been pottering at a cargo lander/lifter and am leaning towards a methane/Lox engine. Whilst methane and LH2 are both able to be made in situ it seems that methane is easier to store.

Yes - I would prefer slush hydrogen as fuel for the interplanetary craft and methane/LOX for the smaller vehicles... not as powerful, but denser.

 

[Columbia42]

One place where I think we could end up wasting fuel is on the hab module's engines. All that module needs to do is deorbit (for this we can use a small, solid fueled engine). As for taking off from the surface, I think we should avoid carrying that engine/fuel (Some of the fuel can be produced in situ) down to the surface on the same flight as the hab module. Instead maybe we could leave room for some kind of detachable engine/fuel tank on the hab module. This could be brought down seperately and attached on the surface in preperation for liftoff.

 

[Voyager]

Or we could have two hab modules and leave one on the surface as a base.

 

[Urwumpe]

One place where I think we could end up wasting fuel is on the hab module's engines. All that module needs to do is deorbit (for this we can use a small, solid fueled engine). As for taking off from the surface, I think we should avoid carrying that engine/fuel (Some of the fuel can be produced in situ) down to the surface on the same flight as the hab module. Instead maybe we could leave room for some kind of detachable engine/fuel tank on the hab module. This could be brought down seperately and attached on the surface in preperation for liftoff.

Yes, that is what I mean with the skycrane concept - have a separate propulsion module/reusable shuttle, that lands the hab module by means of a long tether connection that permits some distance to the surface from the landing engine.

What I don't yet have is a good way to return back to Earth, I am torn between using a Earth Return Vessel (ERV) that fits into the 40 ton landing envelope of the skycrane, and attaching a lighter crew module to the skycrane after landing/refueling on Mars, that rendezvous with the interplanetary spacecraft in Mars orbit.

The ERV would permit a direct return when combined with an inflatable habitat module, the second one would require less mass to be transported to Mars - essentially just a light cabin with a docking port.

 

[Columbia42]

Yes, that is what I mean with the skycrane concept - have a separate propulsion module/reusable shuttle, that lands the hab module by means of a long tether connection that permits some distance to the surface from the landing engine.

What I don't yet have is a good way to return back to Earth, I am torn between using a Earth Return Vessel (ERV) that fits into the 40 ton landing envelope of the skycrane, and attaching a lighter crew module to the skycrane after landing/refueling on Mars, that rendezvous with the interplanetary spacecraft in Mars orbit.

The ERV would permit a direct return when combined with an inflatable habitat module, the second one would require less mass to be transported to Mars - essentially just a light cabin with a docking port.

Oh! I didn't know that we were going to return the hab to LMO via the skycrane. I thought that was just a landing system.

As for returning to Earth, I think the best strategy would be to bring the hab module back to Mars orbit and use the stack that brought us to mars to return to Earth. If the NERVA 2 doesn't have enough fuel for the whole journey (TMI, MOI, TEI and course corrections), than we can send a seperate flight to Mars carrying fuel and supplies for the return trip of the crew. (This flight can be launched in the launch window previous to the one the crew are launched in).

 

[Urwumpe]

Oh! I didn't know that we were going to return the hab to LMO via the skycrane. I thought that was just a landing system.

It is - but it would also have a useful upwards capability, at the expense of the next cargo downward.

As for returning to Earth, I think the best strategy would be to bring the hab module back to Mars orbit and use the stack that brought us to mars to return to Earth. If the NERVA 2 doesn't have enough fuel for the whole journey (TMI, MOI, TEI and course corrections), than we can send a seperate flight to Mars carrying fuel and supplies for the return trip of the crew. (This flight can be launched in the launch window previous to the one the crew are launched in).

I think this is not the best strategy if you want to extend the base over time - i think it is better to let the hab stay on the surface and append the base with new landers and habitats.

Just as reminder - for the way down to mars, we can slow down by aerobraking, but for the way up, we need the full dV. Landing heavy payloads is easier than bringing them back.

 

[Salun]

Well now that we have most of the technical ways to get to mars and the surface. I must ask. What are we gonna do(Aside mine for fuel for the return trip?).

I think the majority of us agree we should Land near Viking, Pathfinder or the MER rovers.

The real question is. Are we gonna have to drive there? Walk, Hitchhike or are we gonna have some sort of aircraft so we can explore all of Mars? Maybe some sort of Martian rover?

Next the Stacks orbit.

Call me Crazy but the way most people talk about its final orbit is circular. When it comes to saving fuel I vote for a highly eccentric elliptical orbit. One that would also a few times provide flybys the Martian moons. It should save fuel on MOI and if it were a real mission provide opportunity to study Mars Surface and its moons. Which are pretty much asteroids.

 

[Izack]

Some figures for Mission Package 1A:
I bumped up the mining/processing assembly to 7 000kg
SMEV = 2 000kg
Fuel refining and storage facilities (empty) = 2 000kg
Combination transport/forklift/dozer thingy = 2 000kg
Various cargo = 1 000kg
Total = 14 000kg

I chose the Ariane 5 as the lift vehicle for this package, as its payload capacity to LEO is 16 000kg.

I was under the impression that the primary engine for this mission was the NERVA-2 gas-core NTR, launched by Ares V.

As for Package 1B, I was thinking of using the STS. That way, it could carry the other 8 astronauts (the first 4 going by Orion or 3 by Soyuz-TMA) as well as 24.4 extra tonnes. How much does the Skycrane weigh? Can the Shuttle carry it?

 

[fireballs619]

Call me Crazy but the way most people talk about its final orbit is circular. When it comes to saving fuel I vote for a highly eccentric elliptical orbit. One that would also a few times provide flybys the Martian moons. It should save fuel on MOI and if it were a real mission provide opportunity to study Mars Surface and its moons. Which are pretty much asteroids.

I, too, would like to study martian moons. I wouldn't want to place this in a priority position, but if it can be accomplished without majorly changing mission plans, I'm all for it. Perhaps a probe can detach from the stack once we're in mars orbit, then rejoin before returning? I don't know if that is realistic, because I'm not that caught up on the mission plan. But if we're gonna be in that part of the neighborhood, why not :thumbup:

 

[Izack]

Perhaps a probe can detach from the stack once we're in mars orbit, then rejoin before returning? I don't know if that is realistic, because I'm not that caught up on the mission plan. But if we're gonna be in that part of the neighborhood, why not :thumbup:

Even the Apollo program brought along a small satellite (Apollo 16 subsat for measuring the Lunar magnetosphere, launched from the SM...I think there's a scenario for it in AMSO)

I am totally against the idea of leaving the interplanetary segment in an eccentric orbit. Quite frankly it is ludicrous. Sure it saves fuel, but it leaves the stack much too far away for the majority of its orbit, and even at periareion it will be going far too fast for a safe rendezvous.

 

[Salun]

Good point. Though maybe we can over time using the moons use a gravity assist to circularize our orbit.

Plan be might be at a latter point towards the end of the mission the stack does a parking orbit burn to loose it eccentricity. Making it safe for a rendezvous.

In that scenario it does make my point of saving fuel pointless on the stack but still we get a awesome view of the moons.

As for launching probes we could put it in the mission plan. But not actually do it. As a sort of"Hey this is what we do now" sort of deal. Rather than waist time making a whole new item that we could have to carry on board.

And on a final note. Why retrieve the probe?hail:) Why not plan it as an impactor?