alexterrell

I think solar electric is fine for hauling large 20 - 100 ton modules
over several months. Meanwhile, the CEV vehicle is sent up on chemical
rockets. Solar thermal is certainly worth investigating, though the
specific impulse is quite low - the only advantage over chemical is
you can use a monopropellant, which is not an issue for cargos launched from Earth.

My point was flexible. We always see pictures of 18m long modules on
the lunar surface. How did they get there? Two or Four H2 / O2 landers
would be needed to land such a thing. For this they would be digitally
linked and operate as one.


This is a whole area that needs to be investigated. Having looked into
the energy requirements for extracting iron, compared to aluminium,
you could be right. However, long term, aluminium will be a more
desirable metal. That doesn't mean that the first extraction will be of iron.

Then perhaps we link this with the iron production and make steel or
titanium cables the main priority. Then we can use reinforced mooncrete for tension structures.


You need a lot of feul to decelerate from 11km/s to 7km/s. I think all
thinking is to use aerobraking for return from the moon, as Apollo did.

If they can be controlled from Earth with a PC and joystick, then they
could be controlled from the moon. But employing someone on the moon
will cost perhaps $100,000 per day, or 100 times what it costs to
employ someone on Earth. If we get a decent sized base, I'd expect
round the clock operations, mostly controlled from Earth.

The fact that this is feasible is a major advantage the moon has over
Mars.

dholmes

I may be miss informed but it would take 4 or 5 years with current systems.
On top of which the solar cells would be damaged by the years in the Van
Allen belts.
Better to get above them and deliver in a year or so a large solar panel to
orbit along with equipment/supplies.


The low energy required to get oxygen out of iron ore not the actual iron
that interested me.
a couple of thousand pounds of oxygen can go a long way.

ool

Yeah, especially a long way home. 70% of the Lunar lander's mass was
fuel they had to bring along from Earth.

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alexterrell

There is currently an ESA probe on the way to the moon. It'll take
about 2 years. However, using this calculation:

Delta V = 4 km/s (not sure of actual requirement in a spiral orbit)
Exhaust Velocity = 20km/s
Propellant fraction = 0.2

Assume vehicle = 1 ton, propellant = 200kg, solar cells = 200kg, cargo
= 600kg

Exhaust energy = 1/2 * 200 * (20,000)^2 = 4E10J

Power from 200kg of solar panels = 20KW.

Transit time = 4E10 / 2E4 seconds = 24 days.

If we halve the fuel mass and the solar panel mass, we get 100 days.
Empty return would be faster, with less fuel, so lets assume 6 months
there and back.

It is possible to make solar panels resistant to van allen radiation.
I'm not sure how.

I do think a rotovator would be even better though.

dholmes

That probe started in GTO if it had started in LEO you would be talking
about 6 years.
Remember almost half your time in LEO is in the shadow of the Earth.
This does not mean not to use it just do not start from LEO.


Most systems today run about 2000kg for 20kw.

This is an area where such craft would shine return missions.
The other is station keeping.


Not without losing efficiency.

alexterrell

Something to add to the to do list.

There is no fundamental reason why solar cells need to be even 1mm
thick - I've heard that 10kg/kw is achievable, though not on the rigid
structures used for current launches.

It also seems a lot of research is going into improving efficiency
measured as W/m2, and not into W/kg. Equally important is ease of
deployment, and later, ease of manufacture from lunar or NEO material.


Why is this? Do you know how this is done? I've heard they need to be
coated in glass, which may add weight, but should have only a small
impact on efficiency.