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To the moon!
Posted: Wed Nov 16, 2022 7:24 am
by Grumble
I didn’t realise the Artemis launch had been conveniently scheduled to fit in with my breakfast, but I happened to find out at about T-10 so I watched with one child. Always good to see a successful launch, especially such an important one
Re: To the moon!
Posted: Wed Nov 16, 2022 9:48 am
by IvanV
Grumble wrote: ↑Wed Nov 16, 2022 7:24 am
...especially such an important one
Why is it important? Repeating what they did many decades ago. Rewarming an old and costly launch system, instead of developing one of the much cheaper ones now available.
For the money, they could have got a much better science yield like preparing Cassini/Galileo style missions to Uranus and Neptune, that would have actually learned something new.
Re: To the moon!
Posted: Wed Nov 16, 2022 11:03 am
by Grumble
I’m more excited by the idea of people walking on the moon than probing Uranus
Re: To the moon!
Posted: Thu Nov 24, 2022 6:52 pm
by sideshowjim
The Artemis project can use the Moon as a stepping stone to further exploration (as there's a lot less fuel required to launch from the moon, and assemble in orbit etc).
But I agree, I'd love another Voyager probe style mission.
Re: To the moon!
Posted: Thu Nov 24, 2022 7:00 pm
by dyqik
sideshowjim wrote: ↑Thu Nov 24, 2022 6:52 pm
The Artemis project can use the Moon as a stepping stone to further exploration (as there's a lot less fuel required to launch from the moon, and assemble in orbit etc).
But I agree, I'd love another Voyager probe style mission.
You've got a long wait for another Voyager style mission. You literally need all the planets to align to make it happen, and think that's an every few centuries thing.
Which is why there's been so many individual missions since.
Re: To the moon!
Posted: Fri Nov 25, 2022 5:51 pm
by IvanV
sideshowjim wrote: ↑Thu Nov 24, 2022 6:52 pm
The Artemis project can use the Moon as a stepping stone to further exploration (as there's a lot less fuel required to launch from the moon, and assemble in orbit etc).
But you have to lift the fuel off the earth and land it on the moon first. And how much fuel does it take to land 1kg of payload on the moon? Is there a net saving? What's it like putting a large rocket on the moon with a launch facility, and fuelling it, and launching it. Hard enough to do it in Florida.
Wernher von Braun did some back of the envelope calculation back in the 50s for a manned Mars mission, on the assumption that you only put a minimal lander on Mars, with enough fuel to lift the humans back off and connect them to fuel food and space craft left in orbit. He had a huge mission size in mind, and there are some efficiency improvements some then. But thermodynamics still rules you. The basic idea is you have a fleet of spacecraft assembled in orbit around earth and sent off to Mars together to orbit Mars. Then you only land what you need on Mars to get you back off again and back to the remaining orbiting fleet. You start making these appalling calculation, how much fuel to do you need to put 1kg of fuel and other requirements in orbit around earth, how much fuel do you need to put 1kg of fuel and other requirements in orbit around Mars, how much fuel to you need to put on Mars to lift 1 kg of payload off Mars and back into orbit around Mars. How much fuel and stuff do you need to get back from Mars orbit to earth. The computations work backwards to give you huge amounts. Wernher von Braun's expedition ended up with about 1000 heavy lifts off earth into earth orbit, but his was a large expedition, with a year on Mars and a large crew. Doubtless it can be considerably scaled back. But the thermodynamics means that the costs in fuel and numerous spacecraft are bound to be enormous, with coordination problems of stuff in space on a scale never before thought about.
Anyone talking about doing it by 2033 or doing it for under $100bn is talking science fiction. This single Artemis rocket has ended up costing over $10bn.
Re: To the moon!
Posted: Fri Nov 25, 2022 6:23 pm
by Gfamily
There's an interesting Everyday Astronaut video and blogpost about the SpaceX methane/oxygen Raptor engine.
It's suggested that these are components that could be formulated on Mars, which would reduce the amount of fuel mass needed to fuel a return journey.
https://everydayastronaut.com/raptor-engine/
It's an interesting read anyway.
Re: To the moon!
Posted: Fri Nov 25, 2022 8:22 pm
by Grumble
IvanV wrote: ↑Fri Nov 25, 2022 5:51 pm
sideshowjim wrote: ↑Thu Nov 24, 2022 6:52 pm
The Artemis project can use the Moon as a stepping stone to further exploration (as there's a lot less fuel required to launch from the moon, and assemble in orbit etc).
But you have to lift the fuel off the earth and land it on the moon first. And how much fuel does it take to land 1kg of payload on the moon? Is there a net saving? What's it like putting a large rocket on the moon with a launch facility, and fuelling it, and launching it. Hard enough to do it in Florida.
Wernher von Braun did some back of the envelope calculation back in the 50s for a manned Mars mission, on the assumption that you only put a minimal lander on Mars, with enough fuel to lift the humans back off and connect them to fuel food and space craft left in orbit. He had a huge mission size in mind, and there are some efficiency improvements some then. But thermodynamics still rules you. The basic idea is you have a fleet of spacecraft assembled in orbit around earth and sent off to Mars together to orbit Mars. Then you only land what you need on Mars to get you back off again and back to the remaining orbiting fleet. You start making these appalling calculation, how much fuel to do you need to put 1kg of fuel and other requirements in orbit around earth, how much fuel do you need to put 1kg of fuel and other requirements in orbit around Mars, how much fuel to you need to put on Mars to lift 1 kg of payload off Mars and back into orbit around Mars. How much fuel and stuff do you need to get back from Mars orbit to earth. The computations work backwards to give you huge amounts. Wernher von Braun's expedition ended up with about 1000 heavy lifts off earth into earth orbit, but his was a large expedition, with a year on Mars and a large crew. Doubtless it can be considerably scaled back. But the thermodynamics means that the costs in fuel and numerous spacecraft are bound to be enormous, with coordination problems of stuff in space on a scale never before thought about.
Anyone talking about doing it by 2033 or doing it for under $100bn is talking science fiction. This single Artemis rocket has ended up costing over $10bn.
Is there any benefit in ease of assembly to using the moon as a staging post?
Re: To the moon!
Posted: Fri Nov 25, 2022 8:29 pm
by Gfamily
Grumble wrote: ↑Fri Nov 25, 2022 8:22 pm
Is there any benefit in ease of assembly to using the moon as a staging post?
If water ice trapped in deep craters (or sub surface regolith) can be used to generate H2 and O2 on the Moon's surface, then it'll be far more energy efficient to lift into orbit than from the Earth's surface.
Re: To the moon!
Posted: Fri Nov 25, 2022 8:35 pm
by Grumble
Gfamily wrote: ↑Fri Nov 25, 2022 8:29 pm
Grumble wrote: ↑Fri Nov 25, 2022 8:22 pm
Is there any benefit in ease of assembly to using the moon as a staging post?
If water ice trapped in deep craters (or sub surface regolith) can be used to generate H2 and O2 on the Moon's surface, then it'll be far more energy efficient to lift into orbit than from the Earth's surface.
I get that, I was suggesting that working conditions might be better in low gravity than microgravity. Might be negated by the presence of moon dust though.
Re: To the moon!
Posted: Sun Nov 27, 2022 10:50 am
by IvanV
Gfamily wrote: ↑Fri Nov 25, 2022 8:29 pm
Grumble wrote: ↑Fri Nov 25, 2022 8:22 pm
Is there any benefit in ease of assembly to using the moon as a staging post?
If water ice trapped in deep craters (or sub surface regolith) can be used to generate H2 and O2 on the Moon's surface, then it'll be far more energy efficient to lift into orbit than from the Earth's surface.
Making H
2 and O
2 out of water takes a lot of energy. You can potentially generate it on the moon, but then you need huge amounts of solar panels, first to melt it - huge energy requirement - then to electrolyse it. And you probably need to do some chemistry on it first, as if it is mucky then that can be a problem for electrolysing it. Then even on the moon you are going to need to expend energy in cooling the hydrogen to 33K to get it in the suitable form for rocket fuel. So some quite large real estate needed just for your solar panels. At least on the moon high latitude isn't going to limit their production to the extent it would on the earth, but to put them at the right angle and not have them shading each other, they'll have to be well spread out.
So how much industrial plant do you need to put on the moon, just to make hydrogen and oxygen? How many J of energy do you have to gather from your solar panels to make 1 J of useful rocket fuel?
And that's only making the fuel...
This remains science fiction for now.
Edited for typos.