Soyuz Lunar Mission

[N_Molson]

What if the crew brings the fuel cells in the Soyuz, and plug them into the LM, which was supplied by the solar panels in "hibernation" mode ?

About the hatches : the docking port provides a clearance of 80 centimeters, which corresponds to the Soyuz. The rear hatch provide a 1 meter clearance (a little more room is better to move with spacesuits).

 

[Urwumpe]

Well, for hibernation, a small solar array is enough. If you launch at the right phase of the moon, you could even use just a small battery, since you get long enough sunlight phases then.

 

[N_Molson]

So it would probably make more sense to attach the solar panel to the descent stage. I only wonder how complex it is to "plug" fuel cells ? Is it possible to lit them before launch ? If not, would the Soyuz be able to provide enough power for that ?

 

[Urwumpe]

So it would probably make more sense to attach the solar panel to the descent stage. I only wonder how complex it is to "plug" fuel cells ? Is it possible to lit them before launch ? If not, would the Soyuz be able to provide enough power for that ?

I wouldn't even plug them in, you can launch them with the LM, they are pretty light and except hydrogen, you just need a bit more oxygen for producing hot water as well with it.

Otherwise, you need larger solar arrays after landing for producing enough energy during the surface stay. And you need really huge batteries, since you need most power during the phase, in which the solar arrays will have to be retracted and not oriented towards the sun.

EDIT: What about having a hibernation module attached at the LM? That contains the solar arrays, the orbit keeping engines and some RCS and the LM is completely in hibernation without the need to be started.

 

[N_Molson]

EDIT: What about having a hibernation module attached at the LM? That contains the solar arrays, the orbit keeping engines and some RCS and the LM is completely in hibernation without the need to be started.

Interesting idea, a "lite" Soyuz Service Module would probably be well-fitted for that.

But again, we'll have to see with the mass budget and our propulsion systems expert

 

[Urwumpe]

Interesting idea, a "lite" Soyuz Service Module would probably be well-fitted for that.

But again, we'll have to see with the mass budget and our propulsion systems expert

Well, we could also use a full service module with solar arrays... reuse.

 

[N_Molson]

The LK engine (RD-858) seems very interesting. The description given of its different modes and throttling ratios is what we need to make something realistic. It uses the same fuel as the Soyuz (N204/UDMH). It includes a back-up engine, which is excellent for the safety.

The main difference is that the LK was supposed to be braked during its descent by a BlockD booster. So we would need larger tanks.

The RD-858 was the primary engine for the Soviet LK manned lunar lander. The propulsion cluster provided the variable thrust needed for a soft landing onto the lunar surface. The same engine was then restarted for lift-off from the moon and injection of the LK into a lunar elliptical orbit. Testing of the engine on the ground and in earth orbital tests confirmed the high reliability of the design.

Also, I like the fact it is used again for the ascent. Leaving more junk on the lunar surface than necessary doesn't seem an excellent idea.

 

[Urwumpe]

It might be also a tiny bit low thrust. I suspect we need more than that. It already needed the strong vernier engines as support.

 

[T.Neo]

Small nitpick: wouldn't it be better if the windows were smaller?

 

[Urwumpe]

Small nitpick: wouldn't it be better if the windows were smaller?

Yes. At least the docking window does not need to be very large.

For landing, a bigger FOV is preferred and we need a good look down.

 

[N_Molson]

The windows have been "reinforced". Still, they should offer a good visibility on the landing site. I made them emissive for better visualisation, that light from the top is awful, I have to change the scenario time to get a better lightning

Concerning the engine, with 4 tons of fuel and 2,5 tons of empty mass, the LM can liftoff easily from the Moon, wich would not be required. So unless the weight goes over 8 tons (which will cause logistics problems), the engine is strong enough.

 

[Thorton]

Are you planning to make 2 stage LM or 1 stage, maybe with detachable tanks?

Btw, i've started working on KVTK tug.

 

[N_Molson]

I like the idea of the 1-stage concept with detachable tanks. Maybe the "spheric" tanks could be replaced by a cylindric one (like the Breeze-M external tank). A smaller tank could be placed between the habitation module and the propulsion module, to feed the engine during the ascent.

 

[Urwumpe]

I think a torus tank would be best, we can then attach the landing gear to the torus tank.

 

[T.Neo]

I know a larger window is (obviously) better, but I keep thinking about the windows of the LM... does the craft really need those seperate side windows, for example?

 

[Urwumpe]

does the craft really need those seperate side windows, for example?

No. :lol:

The landing window could also be smaller and the docking window could be just a lens shaped bullseye.

 

[N_Molson]

I think a torus tank would be best, we can then attach the landing gear to the torus tank.

I'm not sure of that, because fuels tanks are fragile things and should not participate to the structural integrity of the craft, but yes, the legs would stay on the surface anyway, they are clearly dead mass.

I know a larger window is (obviously) better, but I keep thinking about the windows of the LM... does the craft really need those seperate side windows, for example?

I'm not against reducing the windows size again, but I'd like to hear technical arguments. First, what material is used to make them ? I would guess Plexiglass, but I'm not sure. But I know nothing about windows ! I also would guess that their size is limited by the difference of inside / outside pressure, that put a lot of stress on them, and maybe by the vibrations (ever saw a large window vibrate strongly in a bus when the engine runs idle ?). A depressurized module could probably be a big spherical cupola with an engine. But since the LM has to be equalized with a Soyuz TMA, and to start with I don't know how pressurized it is. Here's what I found on Wikipedia, in the article "Soyuz-TMA" :

The life support system provides a nitrogen/oxygen atmosphere at sea level partial pressures.

What means "at sea level partial pressures ?". That the quantities of N2/O2 are the same than at sea level, but what about the actual pressure inside the cabin ?

 

[T.Neo]

If both have the same partial pressure, then that should add up to a total pressure and composition similar to that at sea level.

I think the windows are a type of thermally resistant glass... the shuttle windows have some sort of plexiglass or polycarbonate layer (I think) but this is only internal.

The main stresses would be pressure and thermal. Vibration would also be problematic but not nearly as much, especially in this particular situation.

This spacecraft has it worse than the LM since it is at a higher pressure, STS and station windows (Cupola, etc) would be a good guide here.

 

[Urwumpe]

I'm not sure of that, because fuels tanks are fragile things and should not participate to the structural integrity of the craft, but yes, the legs would stay on the surface anyway, they are clearly dead mass.

Don't underestimate tanks - rockets are 95% tanks.

What means "at sea level partial pressures ?". That the quantities of N2/O2 are the same than at sea level, but what about the actual pressure inside the cabin ?

If N2 is at sea level partial pressure and O2 is at sealevel partial pressure, you have only trace gases left, that could not be at sea level partial pressure.

 

[T.Neo]

Don't underestimate tanks - rockets are 95% tanks.

Indeed. Rocket propellant tanks can support hundreds of tons, at multiple Gs of acceleration...