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Skylon

By Skylon
in Science & Spaceflight

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tater

tater

Posted
Posted (edited)
9 hours ago, mikegarrison said:

Not if you have the rocket at one end of the tether and the living quarters at the other end. How are you going to catch up to that rocket that is now flying away from you?

The image was of 2 BFS tethered together from their noses.

EDIT: I'm told your comment was in reference to an old NASA concept, not the nose to nose, BFS, my bad.

Edited by tater
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sevenperforce

sevenperforce

Posted
Posted
3 hours ago, Lukaszenko said:

There's that, but there's also the sudden need for stairs and things like that. I don't know how much space that would take, but I imagine it's a lot.

Don't have to spin up to 1 gee. Going up to, say, 1/5 of a gee will reduce the load on and length of the tether, and leave you with enough muscle mass to handle Martian gravity, but you'll still be able to jump ten times your body height, so stairs are not necessary.

7 minutes ago, tater said:

The image was of 2 BFS tethered together from their noses.

The reference was to an early nuclear thermal Mars mission, where the living quarters would be tethered opposite the propulsion unit.

Some takeaways from the Mueller speech:

  • Making engine fly 10x you run into "100,000 mile problems" seals wear out, turbine blades and combustion chamber cracks (I bet!)
  • Raptor's TWR will exceed Merlin 1D's (we already knew this)
  • The methane-fueled Raptor is expected to be twice as powerful as the Merlin 1D, with liftoff thrust of 380,000 pounds (and there you have it, folks)
  • Engine development is on track for next year’s anticipated start of short-hop flight tests of the BFR upper-stage spaceship (looks like SpaceX employees in general are very onboard with BFR)
     
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tater

tater

Posted
Posted
44 minutes ago, Rus-Evo said:

I suspect that the weight of cable is a big DV downside.

This is BFS we're talking about. So they take a little less cargo. Besides, carbon fiber is not that heavy, honestly. They only need a few hundred meters.

500m (250m radius), and they spin at 1.17 rpm for Mars gravity.

200m dia and it's 1.84 rpm for martian gravity.

They could do lower g, too, the real point would be to make logistics easier (eating, going to the bathroom, etc). They'd be able to more easily exercise, as well.

8 minutes ago, sevenperforce said:

The reference was to an early nuclear thermal Mars mission, where the living quarters would be tethered opposite the propulsion unit.

Ah, sorry, my bad, it's the SpaceX thread, and I missed that post.

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Lukaszenko

Lukaszenko

Posted
Posted
55 minutes ago, Rus-Evo said:

I suspect that the weight of cable is a big DV downside.

 

Based on this link, I estimate a kevlar cable would weigh about 5 kg/m for a 450 ton BFS at 1g. I don't know how much you want, maybe 100 m? So that's 500 kg, and that's probably waaaay over-engineered.

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DMagic

DMagic

Posted
Posted

It could be an interesting method for helping people adjust to Mars gravity. Start out at 2/3 g, or something like that, and gradually reduce it to the ~1/3 g of Mars.

As for living space design, it seems like everything would already have to be designed vertically, rather than laid out horizontally like an airplane. You are taking off and landing vertically, so it makes sense that the space would be laid out like a tower with many floors connected by ladders.

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kerbiloid

kerbiloid

Posted
Posted
41 minutes ago, sevenperforce said:

but you'll still be able to jump ten times your body height, so stairs are not necessary.

Then helmets are.

42 minutes ago, sevenperforce said:

1/5 of a gee will reduce the load on and length of the tether, and leave you with enough muscle mass to handle Martian gravity

2/5, as Mars's = 0.4

3 hours ago, NSEP said:

If i had a giant spaceship with the internal volume of a big airliner, i wouldn't waste that space on nothing.

They need 27..28 m3 of room per head (for long trips), according to studies. (From several sources).
So, the nothing would be its main cargo anyway.

39 minutes ago, tater said:

This is BFS we're talking about. So they take a little less cargo. Besides, carbon fiber is not that heavy, honestly. They only need a few hundred meters.

500m (250m radius), and they spin at 1.17 rpm for Mars gravity.

200m dia and it's 1.84 rpm for martian gravity.

Then a little change of CoM position, and they get whipped (a wave along the tether) and then tangled.

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sevenperforce

sevenperforce

Posted
Posted
1 hour ago, DMagic said:

It could be an interesting method for helping people adjust to Mars gravity. Start out at 2/3 g, or something like that, and gradually reduce it to the ~1/3 g of Mars.

As for living space design, it seems like everything would already have to be designed vertically, rather than laid out horizontally like an airplane. You are taking off and landing vertically, so it makes sense that the space would be laid out like a tower with many floors connected by ladders.

Tin-tin.

1 hour ago, kerbiloid said:

2/5, as Mars's = 0.4

Right. 1/5 for half of Martian gravity.

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Wjolcz

Wjolcz

Posted
Posted
2 hours ago, Lukaszenko said:

Based on this link, I estimate a kevlar cable would weigh about 5 kg/m for a 450 ton BFS at 1g. I don't know how much you want, maybe 100 m? So that's 500 kg, and that's probably waaaay over-engineered.

Wouldn't carbon fiber be lighter than kevlar though?

Does anyone know how kevlar and carbon fiber degrade in space conditions over time?

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Lukaszenko

Lukaszenko

Posted
Posted
47 minutes ago, Wjolcz said:

Wouldn't carbon fiber be lighter than kevlar though?

Does anyone know how kevlar and carbon fiber degrade in space conditions over time?

Probably, I didn't realize that they made ropes out of the stuff. Makes sense though.

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sevenperforce

sevenperforce

Posted
Posted
6 minutes ago, Barzon Kerman said:

Found this article and it reminded me of a conversation a few pages ago:http://spacenews.com/safety-panel-considers-spacex-load-and-go-fueling-approach-viable/

Critical:

George Nield, another ASAP member and former associate administrator for commercial space transportation at the Federal Aviation Administration, recommended NASA look at overall safety, not just of crews on the spacecraft. “Not only crew safety, but also ground crew safety, is an important factor,” he said. “Where are the risks, and how can they be mitigated, and what is the best overall sequence for safety of the whole?”

 

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Barzon

Barzon

Posted
Posted

Yeah, I just had a quick look then posted the link so I don't really know what it said.

Quote

Tom Mueller, a frustrated engineer at the conglomerate TRW’s aerospace division, who was building a rocket engine for fun in his garage. That—the largest liquid-fueled engine ever built by an an amateur—turned out to be the earliest version of the Merlin,

Bah ha ha! Merlin started off as a hobby engine!:D :sticktongue:

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magnemoe

magnemoe

Posted
Posted
10 minutes ago, sevenperforce said:

Critical:

George Nield, another ASAP member and former associate administrator for commercial space transportation at the Federal Aviation Administration, recommended NASA look at overall safety, not just of crews on the spacecraft. “Not only crew safety, but also ground crew safety, is an important factor,” he said. “Where are the risks, and how can they be mitigated, and what is the best overall sequence for safety of the whole?”

 

I assume the fuel and go idea is that you put astronauts in capsule, redraw ground crew like in any satellite launch, fuel it and launch. 
Any issues and you abort and drain fuel then extract astronauts. In case of fire or over-pressure you use the abort system. 
Ground crew would only work with an dry rocket so they would be safer than Apollo or shuttle missions. 
Downside for astronauts is more ground time in capsule, double in an flight cancel. This is however just an annoyance unless you need to use the restroom. 

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sevenperforce

sevenperforce

Posted
Posted
8 minutes ago, magnemoe said:

I assume the fuel and go idea is that you put astronauts in capsule, redraw ground crew like in any satellite launch, fuel it and launch. 
Any issues and you abort and drain fuel then extract astronauts. In case of fire or over-pressure you use the abort system. 
Ground crew would only work with an dry rocket so they would be safer than Apollo or shuttle missions. 
Downside for astronauts is more ground time in capsule, double in an flight cancel. This is however just an annoyance unless you need to use the restroom. 

Yep.

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Ricktoberfest

Ricktoberfest

Posted
Posted (edited)
On 5/25/2018 at 2:26 PM, magnemoe said:

I assume the fuel and go idea is that you put astronauts in capsule, redraw ground crew like in any satellite launch, fuel it and launch. 
Any issues and you abort and drain fuel then extract astronauts. In case of fire or over-pressure you use the abort system. 
Ground crew would only work with an dry rocket so they would be safer than Apollo or shuttle missions. 
Downside for astronauts is more ground time in capsule, double in an flight cancel. This is however just an annoyance unless you need to use the restroom. 

Didn’t shuttle crews have to be on board for several hours before launch?  Falcon 9 takes much less time to fill than that  

how do the Russians do it? 

Edited by Ricktoberfest
Autocorrect
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