Author Topic: What Could Be Tried on the Moon Before Going to Mars?  (Read 26416 times)

Offline Robotbeat

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Re: What Could Be Tried on the Moon Before Going to Mars?
« Reply #60 on: 05/24/2016 08:08 PM »
CO/O2

What about for the MTV voyage home?
It'd use whatever is convenient. Could be CO/O2, but I'd guess it'd be worth it to use CH4/O2 or H2/O2 (or Argon for electric propulsion). Or send up just water and do the electrolysis in a high-orbit where you have 24-7 sunshine. The relative masses of propellant needs to be taken into account. Nothing is free, things have varying levels of difficulty to obtain so whether it's worth it to use one thing or another depends on the situation.
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Offline Paul451

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Re: What Could Be Tried on the Moon Before Going to Mars?
« Reply #61 on: 05/24/2016 09:33 PM »
My point was about propellantless launch of ISRU propellant from the Moon, where a) propellantless launch is *much* easier than for Earth or Mars due to the much lower orbital velocity and the lack of atmosphere you have to deal with, b) can be less infrastructure intensive than even setting up the ISRU system to feed it payloads, and c) makes a big economic difference to the cost of propellant from the lunar surface.

OTOH, if you have enough activity in cis-lunar space to justify the construction of any form of propellantless launch from the lunar surface, it implies you've already solved whatever problem you are trying to solve with propellantless launch.

Offline Lar

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Re: What Could Be Tried on the Moon Before Going to Mars?
« Reply #62 on: 05/24/2016 10:02 PM »
Propellantless launch, when practical (it's tons more practical on the moon than either Mars or Earth) dramatically cuts down on the amount of mining and infrastructure you need in order to support a given rate of propellant export. For the Moon, there are options for propellantless launch that could be landed in a single ACES/Xeus landing that could cut the amount of prop you'd need to produce on the moon by nearly half. Half the required infrastructure, half the required landings.
I want to follow up on this... is there a paper somewhere I should go read? To me propellantless means magnetic catapult. Even at reeealllllly high acceleration I'd assumed you need quite a lot of mass in a launcher.  When you say "could be landed"  what do you mean? As a kit that someone has to put together? With some ISRU components? Or self contained? Or do you mean something that unrolls/unfurls self deploys? Does the kit include the solar cells or NTU to power it and the batteries or is that assuming an existing ISRU plant that powers this for a bit?
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline Lar

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Re: What Could Be Tried on the Moon Before Going to Mars?
« Reply #63 on: 05/24/2016 10:05 PM »
Propellantless launch, when practical (it's tons more practical on the moon than either Mars or Earth) dramatically cuts down on the amount of mining and infrastructure you need in order to support a given rate of propellant export. For the Moon, there are options for propellantless launch that could be landed in a single ACES/Xeus landing that could cut the amount of prop you'd need to produce on the moon by nearly half. Half the required infrastructure, half the required landings.
I want to follow up on this... is there a paper somewhere I should go read? To me propellantless means magnetic catapult. Even at reeealllllly high acceleration I'd assumed you need quite a lot of mass in a launcher.  When you say "could be landed"  what do you mean? As a kit that someone has to put together? With some ISRU components? Or self contained? Or do you mean something that unrolls/unfurls self deploys? Does the kit include the solar cells or NTU to power it and the batteries or is that assuming an existing ISRU plant that powers this for a bit?
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline jongoff

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Re: What Could Be Tried on the Moon Before Going to Mars?
« Reply #64 on: 05/24/2016 11:59 PM »
My point was about propellantless launch of ISRU propellant from the Moon, where a) propellantless launch is *much* easier than for Earth or Mars due to the much lower orbital velocity and the lack of atmosphere you have to deal with, b) can be less infrastructure intensive than even setting up the ISRU system to feed it payloads, and c) makes a big economic difference to the cost of propellant from the lunar surface.

OTOH, if you have enough activity in cis-lunar space to justify the construction of any form of propellantless launch from the lunar surface, it implies you've already solved whatever problem you are trying to solve with propellantless launch.

I disagree. As I mentioned to Chris, I see some propellantless launch options that could be put in place with a single ACES/Xeus lander. And halving the amount of lunar LOX/LH2 you need to deliver a kg of LOX/LH2 to LEO makes a huge difference.

~Jon

Offline jongoff

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Re: What Could Be Tried on the Moon Before Going to Mars?
« Reply #65 on: 05/25/2016 12:01 AM »
I want to follow up on this... is there a paper somewhere I should go read? To me propellantless means magnetic catapult. Even at reeealllllly high acceleration I'd assumed you need quite a lot of mass in a launcher.  When you say "could be landed"  what do you mean? As a kit that someone has to put together? With some ISRU components? Or self contained? Or do you mean something that unrolls/unfurls self deploys? Does the kit include the solar cells or NTU to power it and the batteries or is that assuming an existing ISRU plant that powers this for a bit?

I've been meaning to do a blog post on this, but it's been a previous topic on this forum (hint, hint). But yeah, I think a single ACES/Xeus lander could land the main system and the rest of the "kit" to setup a specific type of propellantless launch system that could put 1mT payloads into lunar orbit on a regular basis.

~Jon

Offline Lar

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Re: What Could Be Tried on the Moon Before Going to Mars?
« Reply #66 on: 05/25/2016 02:13 AM »
Need a better hint, search function is not the best :)
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline Warren Platts

Quote from: Robotbeat
Nothing is free, things have varying levels of difficulty to obtain so whether it's worth it to use one thing or another depends on the situation.

Right. And we know for a fact that obtaining lunar materiel is not worth it...  :-X



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Offline A_M_Swallow

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Re: What Could Be Tried on the Moon Before Going to Mars?
« Reply #68 on: 06/05/2016 08:28 PM »
Solar Tubes filled with sand or dust to collect sunlight are a simple ISRU technology. On the Moon we may not even need the glass, just a metal or plastic tube.

Video

The heat can be used directly to warm water. There should be sufficient heat to create electricity using a low temperature difference Sterling engine. Nitrogen, argon or carbon dioxide can be used as the working gas.

Offline savuporo

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Re: What Could Be Tried on the Moon Before Going to Mars?
« Reply #69 on: 08/13/2017 11:47 PM »
Bump

http://interestingengineering.com/concrete-gravity-trains-may-solve-energy-storage-problem/

Quote
This technology is essentially a land based train that takes excess electrical energy and stores it through potential energy gained in large train masses. In rudimentary terms, itís the equivalent of pushing a large rock up a hill when you have the energy so you can push it down later when you need more energy.
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Offline Lampyridae

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Re: What Could Be Tried on the Moon Before Going to Mars?
« Reply #70 on: 08/16/2017 11:16 AM »
Bump

http://interestingengineering.com/concrete-gravity-trains-may-solve-energy-storage-problem/

Quote
This technology is essentially a land based train that takes excess electrical energy and stores it through potential energy gained in large train masses. In rudimentary terms, itís the equivalent of pushing a large rock up a hill when you have the energy so you can push it down later when you need more energy.


Those are designed for a short spurt of energy to stabilise the grid (a tricky thing). Not all-night power.

Yeahhhhh... wildly inefficient from a volume: power perspective and on the Moon, six times less efficient than *that.*
« Last Edit: 08/16/2017 11:17 AM by Lampyridae »
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Offline Lampyridae

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Re: What Could Be Tried on the Moon Before Going to Mars?
« Reply #71 on: 08/16/2017 11:18 AM »
I want to follow up on this... is there a paper somewhere I should go read? To me propellantless means magnetic catapult. Even at reeealllllly high acceleration I'd assumed you need quite a lot of mass in a launcher.  When you say "could be landed"  what do you mean? As a kit that someone has to put together? With some ISRU components? Or self contained? Or do you mean something that unrolls/unfurls self deploys? Does the kit include the solar cells or NTU to power it and the batteries or is that assuming an existing ISRU plant that powers this for a bit?

I've been meaning to do a blog post on this, but it's been a previous topic on this forum (hint, hint). But yeah, I think a single ACES/Xeus lander could land the main system and the rest of the "kit" to setup a specific type of propellantless launch system that could put 1mT payloads into lunar orbit on a regular basis.

~Jon

Like a whopping big trebuchet, sling etc?
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Offline savuporo

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Re: What Could Be Tried on the Moon Before Going to Mars?
« Reply #72 on: 08/16/2017 11:39 AM »
Yeahhhhh... wildly inefficient from a volume: power perspective and on the Moon, six times less efficient than *that.*
Unless .. you are using local materials.
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Offline Lampyridae

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Re: What Could Be Tried on the Moon Before Going to Mars?
« Reply #73 on: 08/16/2017 12:51 PM »
Yeahhhhh... wildly inefficient from a volume: power perspective and on the Moon, six times less efficient than *that.*
Unless .. you are using local materials.

Train tracks are heavy. You *could* use a simple winch and pulley system. But then you have a lot of bracing etc etc etc. And it's still six times less energy storage than on Earth. Gravity storage is woefully weak.

Then there's lunar dust getting in the gears.
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Offline savuporo

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Re: What Could Be Tried on the Moon Before Going to Mars?
« Reply #74 on: 08/16/2017 04:49 PM »
Energy storage tends to be heavy any way you slice it. Using local materials would obviously be beneficial, question is at what stage do you try to do that, and how high tech can you get.
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Offline TrevorMonty

When comes to surviving 14 day lunar night here 3  options   
1) Nuclear.
2) Space Based Solar power  beamed to surface.
3) LH/LOX. Can generate 2kW/hr per kg, but takes lot more than that to convert it back from water to LH/LOX.

Offline Paul451

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Re: What Could Be Tried on the Moon Before Going to Mars?
« Reply #76 on: 08/17/2017 12:46 AM »
Minor aside:

this would be to prove that the notion of glass domes would or would not have been a viable on the moon.

Domes are compression structures, they are rarely viable when containing a higher pressure (such as air, in a vacuum.) If you are containing pressure, it is, by definition, a pressure vessel and hence should be shaped like a pressure vessel.

(Even if you pile mass on top of the dome to artificially outweigh the force from the contained gas, that gas is still trying to blow out the sides, particularly where the floor joins the side (and that's assuming a gas-tight floor.) Hence the optimal shape would still be a classic pressure-vessel, but "squashed" by the top mass. A low, oblate spheroid, or elongated, ellipsoidal equivalent.)


[Nothing to do with energy storage, just one of those SF tropes that annoys me.]

Offline Lampyridae

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Re: What Could Be Tried on the Moon Before Going to Mars?
« Reply #77 on: 08/17/2017 07:48 AM »
Energy storage tends to be heavy any way you slice it. Using local materials would obviously be beneficial, question is at what stage do you try to do that, and how high tech can you get.


17MJ. That's what you get with 100 tonnes of regolith on a 1km track at 100m elevation.

Equivalent to a 20kg lithium battery.
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Offline Lampyridae

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Re: What Could Be Tried on the Moon Before Going to Mars?
« Reply #78 on: 08/17/2017 07:49 AM »
Minor aside:

this would be to prove that the notion of glass domes would or would not have been a viable on the moon.

Domes are compression structures, they are rarely viable when containing a higher pressure (such as air, in a vacuum.) If you are containing pressure, it is, by definition, a pressure vessel and hence should be shaped like a pressure vessel.

(Even if you pile mass on top of the dome to artificially outweigh the force from the contained gas, that gas is still trying to blow out the sides, particularly where the floor joins the side (and that's assuming a gas-tight floor.) Hence the optimal shape would still be a classic pressure-vessel, but "squashed" by the top mass. A low, oblate spheroid, or elongated, ellipsoidal equivalent.)


[Nothing to do with energy storage, just one of those SF tropes that annoys me.]

Or my favourite: the spiralled glass turd.
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Offline Asteroza

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Re: What Could Be Tried on the Moon Before Going to Mars?
« Reply #79 on: 08/18/2017 08:59 AM »
When comes to surviving 14 day lunar night here 3  options   
1) Nuclear.
2) Space Based Solar power  beamed to surface.
3) LH/LOX. Can generate 2kW/hr per kg, but takes lot more than that to convert it back from water to LH/LOX.

2a) Earth based power beamed to the surface (if you are on the lunar nearside and have multiple earth beaming stations)

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