If gathering gases from the upper atmosphere doesn't work...

Maybe they could point it towards a spacecraft to get above Low Earth Orbit. The idea here is to get high ISP and high thrust directed at a spacecraft in order to increase useful mass fraction.

It would work on similar principles as the nuclear thermal, but instead of nukes doing the work, a solar thermal solution is employed instead. This would be a variation on the Parkins device.

A solar collector as described in an earlier post would supply the energy. It would focus the energy on an aeroshell, which would get heated up to high temperatures. Liquid hydrogen would be used to keep the aeroshell from melting, and the heated hydrogen would be used as the reaction mass.

An ISP of a thousand seconds would reduce the amount of fuel needed. Compared to a hypergolic engine used in Apollo the mass fraction might well be tripled.

If a fast transit to Mars is desired, then one can post it at a LaGrange point, and have to accelerate the spacecraft to Mars at a high velocity. Perhaps it would get there in 45 days.

The spacecraft could be kept light, so the amount of fuel would needed would not be excessive. However, you'd need to slow down once you got there. Therefore, post another one at one of the Martian moons that would slow down the spacecraft once it got there.

The idea here is really to use the sun as the energy source as opposed to onboard fuel. You'd need a series of "stations" that would boost the spacecraft up from low orbit, and from there to interplanetary destinations. At the destination, you could have a station that would help the craft slow down in the same manner-- a retro rocket type deceleration maneuver.

 

Obama himself said that space has to have an economic basis to it

Hence there has to be an economic rationale for its existence.

Is that possible?

Just carrying forward a bit on my peregrinations on the subject of Lox-Leo.

The latest is about the economics of it. If the economics doesn't make sense, then it won't be done. So how does these economics work?

I'm looking at it in terms of how many launches from the ground that it will make unnecessary. It looks like Starship will need about 10 launches for re-fueling, so that it can go to places beyond low Earth orbit.

If you can reduce that number significantly, then Lox-Leo would at least make more sense that launching from the ground.

Other questions need to be answered though. How much does it take to service these facilities? If it doesn't net out positive, then it doesn't make sense. I don't have some numbers to toss around. There's this one number that might be handy. That number is the number of pounds of thrust that can be generated per MW of beamed energy from GEO. This will determine how much of a facility will be needed to generate the energy.

I think it is 50 pounds per MW. But that could be wrong. If it is correct, let's say that 12k lbs of thrust are needed. I got that number from what the OMS thrusters on the Shuttle needed in order to finish its ascent into orbit. The main engines were good for 98% of orbital velocity. The OMS thrusters had to do the rest.

If memory serves, the Shuttle massed out at 200k lbs. Let's assume that the lox-leo device masses out at that. In order to maintain orbit, you may need 12k lbs of thrust.

To generate 12k of thrust, then you need some multiple of MW of 50 MW increments in order to do the trick. That would be 12000/50 equals 240 MW.

Something less than 1 sq mile of solar panels might do the trick.  You'd have to figure the upkeep of these massive structure in the calculations.  (Not done here.)

It would have to be converted to an energy source to beam to the collecting vessel so as to maintain 12k of thrust for whatever amount of time is needed in order to maintain orbital velocity.

Once you know that, then perhaps you can calculate how much you can collect before having a full tank. This may require even more energy. Indeed, you may even have to count on that. ----12:58 PM, 12/14/24:



7:43 PM:



The 50 MW part is correct, according the source I was thinking about. ( The Nuclear Rocket )

Some reading of this Wikipedia source would seem to indicate that whatever gases found up there may not be what is down at sea level. Hmmm. This may not work like I thought it might. There's a lot of sodium up there!

Instead of space solar on the ground, use it to power other spacecraft from geostationary orbit

 

Consider this space-solar type proposition studied in the late 70's:

 

 

It would consist of a large collector, some 38 sq. miles in area, covered with photovoltaic cells....

 

it would convert solar into microwave power for transmission to rectennas on Earth. The rectennas would re-convert the energy back into electricity that would go into the grid...

 

Such a satellite would mass out at 100,000 tons, and produce 10 Gigawatt of power continuously. It would orbit at a geostationary orbit some 22k miles above earth.

 

 

A few observations here: 1) The collectors are too large. It would take a lot of resources to monitor and service these massive satellites. 2) 10 Gigawatts is a lot of power. That would be the equivalent of several Hoover Dams. 3) 100,000 tons is a lot of mass to lift, even for Starship.

 

You wouldn't need nearly that much power for the atmospheric gas collectors (Lox-Leo). It would not have to be continuous. Energy could be stored and then beamed onward to the spacecraft on an as-needed basis.

 

The Parkins concept posited the use of lead-acid car batteries for powering massive rockets to space from the ground. If that could be achieved, could something that didn't require nearly that much power be used in space instead?

 

 

 

A belated speculation alert for that one.