Refueling off celestial bodies

[Spacescifi]

 

So lately methane is popular as a rocket fuel, but when and if we get a much larger space fleet plying the solar system, what will be the most likely fuel source we go after on other worlds?

Furthermore what kind of processing equipment does one need on a spaceship to process their own fuel from space rock/dirt/ice. Namely to separate elements to get water or specific gases?

Is such processing equipment large and heavy and taking up a lotta space on a spaceship?

If so ships would have to specialize roles.

Is gas giant skimmed gas easier to process into liquid fuel than space rock or space dirt?

 

Here is what I surmise:

 

Moon: Ground zero for fuel exploitation.

Mars: It should not be ground zero for resource exploitation as far as I am concerned. Too far. Maybe later.  But resources could definitely be taken here.

Venus: Haha.... okay seriously, this is like a maybe if you get some airships to skim the upper atmosphere and somehow stage rocket or orion pusher plate gas back to orbit to transfer gases to the orbiting spaceship. Orion pusher plate shuttles with belly lander rockets and a tail pusher plate. Sounds crazy but could actually avoid the need for staging due to the high thrust to weigh ratio of a nuclear pulse unit vs tanks of liquid fuel,and any ship can carry dozens or hundreds of pulse bombs.

All gas planets: Ditto.

 

Your thoughts?

 

 

Edited September 11, 2019 by Spacescifi
Pulse unit

[Nightside]

asteroids and ring ice would be a good source of water for props.

[Spacescifi]

38 minutes ago, Nightside said:

asteroids and ring ice would be a good source of water for props.

 

Acknowledged, but you still need processing equipment to extract fuel from the ice/rock, unless you have significant amounts of antimatter available to mix wiith it.

 

My question is, what kind of machinery/processing equipment must future spaceships take with them if they plan on processing and refining space rocks, ices, and gases?

[Guest]

For rock and ice, you just need a heater and a small centrifuge. Simply heat up the ice/rock mixture until it dries out, then inject inert gas (nitrogen will do) to push the water vapor towards the center of the centrifuge. In the center, have a condenser to, well, condense the water vapor out of nitrogen. There you go - pure, distilled water for you to use. It really doesn't require much processing.

In fact, you can do the same with solid methane, though the condenser will have to be quite beefy due to low temperatures involved.

[Spacescifi]

43 minutes ago, Dragon01 said:

For rock and ice, you just need a heater and a small centrifuge. Simply heat up the ice/rock mixture until it dries out, then inject inert gas (nitrogen will do) to push the water vapor towards the center of the centrifuge. In the center, have a condenser to, well, condense the water vapor out of nitrogen. There you go - pure, distilled water for you to use. It really doesn't require much processing.

In fact, you can do the same with solid methane, though the condenser will have to be quite beefy due to low temperatures involved.

 

Huh? How heavy will the equipment be?

Say I want to process a ton of  ice every four hours?

Is that asking for too much? In that the equipment would be so heavy I could only deorbit it in separate modules and launch it via staging onlly?

Also what equipment to process ore into metals. I know centrifuges are great, but dealing with molten metal in orbit will be... interesting.

Radiators and centrifuges here we come!

[Terwin]

Producing rocket fuel from raw resources is a very energy intensive process.  While the actual production bits might not be large or heavy, their power needs will necessitate a large power supply.

Turning 1 ton of ice at 0c to steam at 100c would take 2.73 GJ (2.73x10^9 joules) over 4 hours requires  ~190KW, then another GW to split that water into oxygen and hydrogen.

So it would take the full output of a 1.2GW power plant to convert a ton of barely frozen ice to steam to separate it from most impurities, and then split that into oxygen and hydrogen (assuming a full-process efficiency > 99% and not counting any sort of harvesting/pumping/compression/cooling/storage).

 

 

 

[Spacescifi]

3 hours ago, Terwin said:

Producing rocket fuel from raw resources is a very energy intensive process.  While the actual production bits might not be large or heavy, their power needs will necessitate a large power supply.

Turning 1 ton of ice at 0c to steam at 100c would take 2.73 GJ (2.73x10^9 joules) over 4 hours requires  ~190KW, then another GW to split that water into oxygen and hydrogen.

So it would take the full output of a 1.2GW power plant to convert a ton of barely frozen ice to steam to separate it from most impurities, and then split that into oxygen and hydrogen (assuming a full-process efficiency > 99% and not counting any sort of harvesting/pumping/compression/cooling/storage).

 

 

 

Wow. If the power thay is required is that high it may take too much reactor mass to justify it on a ship.

 

Which kills asteroid in situ spacecraft processing.. Moon base mining and processing is still viable though.

[sevenperforce]

The most probable chain is going to be the use of small, unmanned, one-way probes to visit and analyze candidate asteroids, followed by a larger roboprobe (perhaps using a solar sail) to shepherd the candidate asteroid to a central processing site in orbit.

Without a non-rocket-based launch system, it doesn't make sense to do processing on the surface. If you can use a maglev on the moon to fire your cracked propellants into orbit, great; otherwise you're better off doing the refining in orbit to begin with.

[Spacescifi]

10 minutes ago, sevenperforce said:

The most probable chain is going to be the use of small, unmanned, one-way probes to visit and analyze candidate asteroids, followed by a larger roboprobe (perhaps using a solar sail) to shepherd the candidate asteroid to a central processing site in orbit.

Without a non-rocket-based launch system, it doesn't make sense to do processing on the surface. If you can use a maglev on the moon to fire your cracked propellants into orbit, great; otherwise you're better off doing the refining in orbit to begin with.

 

Upfront costs are higher with a moon base but so are profits in the long run.

 

Once the base and magrail are built, the base could process and mine far more in less time than it would take to select and hunt down profitable asteroids.

[sevenperforce]

5 minutes ago, Spacescifi said:

Upfront costs are higher with a moon base but so are profits in the long run.

Once the base and magrail are built, the base could process and mine far more in less time than it would take to select and hunt down profitable asteroids.

With a magrail, the surface-based approach is far more successful, yes.

[StrandedonEarth]

9 hours ago, Spacescifi said:

Wow. If the power thay is required is that high it may take too much reactor mass to justify it on a ship.

You can use a smaller power plant if you don't need to process 1 ton in 4 hours, Dropping it to 1 ton per 24hr day drops the power requirement to ~200MW, or just 10MW if you can wait 20 days per ton. Given typical interplanetary transit times, if the processing plant is robotic then what's the hurry?

[Spacescifi]

3 hours ago, StrandedonEarth said:

You can use a smaller power plant if you don't need to process 1 ton in 4 hours, Dropping it to 1 ton per 24hr day drops the power requirement to ~200MW, or just 10MW if you can wait 20 days per ton. Given typical interplanetary transit times, if the processing plant is robotic then what's the hurry?

 

Good points you made. I guess I was thinking of the scifi humanoid space miner, but givem the power requirements versus mass which is always expensive in space, likely human crewed ships will be specially designed for FAST travel. I am talking project Orion pusher plates being like the airliners of the solar system.

 

Whereas robotic mining ships will be the slowest and probably the heaviest spacecraft around once loaded with rock. Not to mention all the processing equipment.

Ha... a human ship could even rendezvous with a mining ship to get a chemucal propellant fill up.

Mining ships are mobile fuel bases... just really slow.

[kerbiloid]

Why need a chemical fuel mined on asteroids? Its ISP is puny, its delta-V is ridiculous and hardly sufficient even to send 10% of it to the Earth.
The asteroid belt is so far that you need years to get there and back. So, to visit them you already must have a gas core or a fusion reactor and artificial gravity.
So, on the asteroids you at most need to mine any kind of ice as inert medium to be accelerated by external heating.

[Spacescifi]

34 minutes ago, kerbiloid said:

Why need a chemical fuel mined on asteroids? Its ISP is puny, its delta-V is ridiculous and hardly sufficient even to send 10% of it to the Earth.
The asteroid belt is so far that you need years to get there and back. So, to visit them you already must have a gas core or a fusion reactor and artificial gravity.
So, on the asteroids you at most need to mine any kind of ice as inert medium to be accelerated by external heating.

I know. You could get somewhat longer exhaust burn times with a NTR chemtcal propellant, and therein lies how chemical fuels mighr still prove useful.

Looking at a scifi future, if mankind ever produces copious amounts of antimatter and a foolproof storage system, and way to manage the waste heat, then an antimatter thermal rocket chemical propellant could fly for days on end at 1g.

For that matter, it could even be an SSTO, although on the initial liftoff it will likely rely on rocket stages that will detach to save fuel for space travel.