Death Via Stainless Steel Hull.

[YNM]

4 hours ago, tater said:

One concept is putting the hab inside propellant tanks (or surrounded by them)---and hydrogen is a good propellant (though a PITA to deal with).

Wouldn't that mean cryogenic living space ? I don't want to live inside a liquid hydrogen.

[kerbiloid]

27 minutes ago, YNM said:

Wouldn't that mean cryogenic living space ? I don't want to live inside a liquid hydrogen.

+1
The habitat module should be surrounded by hypergolics.

[Spacescifi]

1 hour ago, YNM said:

Wouldn't that mean cryogenic living space ? I don't want to live inside a liquid hydrogen.

 

Another example of reality being nothing like scifi.

Space is arguably the most hostile environment to lo life known.

 

It would pribabably be best to use the robo-ships to push a big asteroid inti LEO. It would take several decades, but once there you woul dtill into it and turn it into a giant rock-et with processing facilities to extract liquids/gases that are used for obboard rockets.

In the end, it would have far more shielding and mass,than we could get to space withouy rezorting to many launches.

[tater]

2 hours ago, YNM said:

Wouldn't that mean cryogenic living space ? I don't want to live inside a liquid hydrogen.

Nah, You put tanks around the crew quarters. That Lockheed Martin Mars basecamp concept does this.

Space travel is going to be radiation limited for a long time. Astronauts will make a trip someplace like Mars, and will get grounded for hitting their lifetime exposure limit. The Moon is less of an issue, you cover a base with regolith, and the travel time is short.

With Z-pinch and other fusion actively being worked on, travel times could be reduced, too.

[Guest]

2 hours ago, YNM said:

Wouldn't that mean cryogenic living space ? I don't want to live inside a liquid hydrogen.

Actually, no. You'd just need to put a small amount of vacuum between you and the LH2, and make supports out of a good insulator. Remember, "cold" isn't radiated, heat is. If anything, you'd have to put thermal blankets to protect the hydrogen from heat radiated from your crew module.

52 minutes ago, Spacescifi said:

Space is arguably the most hostile environment to lo life known.

Hardly. Space is downright hospitable compared to something like Venus. You don't need crazy amounts of radiation shielding, yes it's a concern, but not as much as people fear. Not to mention improved medicine might make cancer a non-issue in the future. It's not some magical disease, just a very varied one, and if detected early on, it's very much treatable even now. It kills people because, in most cases, it doesn't get detected in time, because people don't test themselves with any sort of regularity. With radiation exposure, you know that you have to start looking for cancer as soon as possible.

[YNM]

2 hours ago, Dragon01 said:

Remember, "cold" isn't radiated, heat is.

Well I still radiate heat from the warm living quarter onto the tanks... that means now the tanks requires more cooling ? more insulation ? idk.

2 hours ago, tater said:

You put tanks around the crew quarters.

Yeah but we'd still have to make linkages. Nothing magically just stays apart without any reaction being transmitted through.

[tater]

8 minutes ago, YNM said:

Yeah but we'd still have to make linkages. Nothing magically just stays apart without any reaction being transmitted through.

Yeah, so some habitation area heat accelerates H₂ boiloff.

[tater]

Here's the LockMart concept:

The "Habitat" area is sleeping, and sits inside where the gold mylar covered ZBO tanks are for radiation shielding. Any heat transfer from the hab is dealt with by the ZBO system.

[farmerben]

There are a host of studies showing that hibernating mammals are able to survive higher doses of radiation.  And that hibernation can increase the chances of cancer going into remission.  

It looks promising that we will find a way to induce hibernation in humans for at least a few days at a time.  

For a Mars and back mission with no special technology, people can take the dose, with maybe a 1-2% chance of cancer.  

 

[kerbiloid]

14 minutes ago, farmerben said:

There are a host of studies showing that hibernating mammals are able to survive higher doses of radiation.  And that hibernation can increase the chances of cancer going into remission.  

We have this in KSP, the DeepFreeze mod. Iirc, 90% chances to wake up.

I'm afraid, no freezer will be used ever except for food. Only a stasis field.
In other words, when they invent an artificial gravity to switch it on/off, same effects will allow to freeze atomic motion in a chamber for a while.

And unlikely it will come sooner that 500 km/s ISP*g thermonukes.

Edited October 3, 2019 by kerbiloid

[YNM]

10 hours ago, tater said:

The "Habitat" area is sleeping, and sits inside where the gold mylar covered ZBO tanks are for radiation shielding. Any heat transfer from the hab is dealt with by the ZBO system.

Hmm, yeah...

Just... make sure it doesn't end up like a 100x worse version of Apollo 13.

[tater]

15 minutes ago, YNM said:

Just... make sure it doesn't end up like a 100x worse version of Apollo 13.

"Stir the tanks."

[kerbiloid]

And btw the heavy radprotection is another argument against centrifugal artificial gravity, as you need either superheavy modules to rotate, or a superheavy drum to surround them.

Edited October 4, 2019 by kerbiloid

[YNM]

4 hours ago, kerbiloid said:

btw the heavy radprotection is another argument against centrifugal artificial gravity, as you need either superheavy modules to rotate, or a superheavy drum to surround them.

We only need to judge which one is more detrimental - radiation, or lack of gravity... probably find a compromise between that.

 

But yeah. Space travel is hard for us surface-dwellers.

Edited October 4, 2019 by YNM

[kerbiloid]

Just now, YNM said:

probably find a compromise for that.

Speed is.

[farmerben]

10 hours ago, kerbiloid said:

And btw the heavy radprotection is another argument against centrifugal artificial gravity, as you need either superheavy modules to rotate, or a superheavy drum to surround them.

Zubrin's idea to tether two spacecraft together solves that.  If the tether is much longer than you need then it takes fairly little propellant to spin up and spin down.  A tiny puff of propellant is enough to initiate spin and put tension in the tether.  Then spool out for more torque on the next puff.  Then reel in to increase angular velocity.   Reverse the process to spin down.  

btw.  Does anybody know where the docking ports for Space X Starship are located?  Have they described their refueling mechanisms?.

[Spacescifi]

23 minutes ago, farmerben said:

Zubrin's idea to tether two spacecraft together solves that.  If the tether is much longer than you need then it takes fairly little propellant to spin up and spin down.  A tiny puff of propellant is enough to initiate spin and put tension in the tether.  Then spool out for more torque on the next puff.  Then reel in to increase angular velocity.   Reverse the process to spin down.  

btw.  Does anybody know where the docking ports for Space X Starship are located?  Have they described their refueling mechanisms?.

 

I like the idea, but how long we talking? For example, two 500 meter wide spacecraft?

Bigger spaceships will require greater length to get proper rotation going.

And the reel line must be strong enough not to snap.

Edited October 4, 2019 by Spacescifi

[farmerben]

17 minutes ago, Spacescifi said:

 

I like the idea, but how long we talking? For example, two 500 meter wide spacecraft?

Bigger spaceships will require greater length to get proper rotation going.

And the reel line must be strong enough not to snap.

 

Say we want 1/3g of artificial gravity using two 150 ton spacecraft.  Operating length is determined by the Coriolis forces which humans can handle, around 30 ft is the minimum operating length.  The more length the better.  

So a 50 ton cable is about 1" thick steel weighing about 2 lbs/foot.  That's a minimum 60 lbs of steel cable.  Multiplying the cable length, divides the amount of propellant needed to spin up and spin down.  

Kevlar is ten times stronger and six times lighter.  So we can operate two spinning starships on 1 lb of cable.  Multiply that for added capability and safety...

 

IIRC Zubrin's idea was ship in which the payload detatches from the propellant tanks for the two ends of the tether