Discussion Powell & Pelligrino's Skytrain (aka ISV Venture Star)

[jangofett287]

At this point, for convenience, I will post a link I posted in the thread that spawned this one: [ame]http://en.wikipedia.org/wiki/Space_colonization[/ame]
There is a lot of good information there, and there are the links and references for those interested in further reading.

 

[Hlynkacg]

It would probably be less of a whipple shield and more of a... shield. Just a flat plate. At that range the pressure on it from the exhaust would probably be pretty low too, so it wouldn't need to be majorly reinforced. The temperature parameters aren't all that high, it'd probably be rather easy, engineering wise, to cope with. The only problem is getting a shield large enough to shield the centrifuge...

Depending on how much shielding is required we might not need to shield the entire arc of the centerfuge. Just reinforce the walls of the Hab that face "forward".

Out of your 1 800 000 kg cargo, it shouldn't be difficult to accomodate 450 people if 4000 of mass is allocated per person. A start-out of 450 people is already quite a large base, in a few flights you would have enough people to start a genetically viable colony.

That's the idea, even if hibernation or "cryo-sleep" is impractical I imagine this spacecraft as an interplanetary Mayflower.

I would say, merge the pilots and engineers together, so instead of having 2 engineers and 2 pilots, have four engineer-pilots, that all share eachother's jobs and responsibilities (because it should be possible to do so).

Fair enough 4 "Crewmen" and a Doctor. I still think there would be a level of specialization though. Even if everyone is capable of doing everyone else's job you'd still want to designate a Captain, Navigator, Engineer etc simply for the sake of having a "Chain of command".

 

[Eli13]

In the movie near the start you can see multiple "doctor" type characters waking other passengers up from cryo-sleep. So i would think 'a Doctor' is silghtly inaccurate. Unless you are talking about a 'head of the med bay' sort of thing.

EDIT: But whether or not you are including cryo bays is not my descision. Or other crew members for that matter.

 

[T.Neo]

The ISV is supposed to have something like 20 doctors. When you've got 200 odd humansicles onboard, and you need them to all wake up properly, that sort of support would be a pretty good idea.

On the other hand, you can put people in another kind of stasis- induced hibernation. In this case, their biological functions are still... functioning and they need nourishment and oxygen, but at a far reduced rate to that normally. The only hitch is that you'd probably still get microgravity degeneration, and it might even be slightly worse than during normal life in space. Maybe you can reduce muscle degeneration with electrostimulation, but this would of course increase nutritional requirement and would only do so much.

 

[Eli13]

So its almost a dilemma. But I think we should remember its a 'precursor' to the ISV so maybe cryo tubes arent included. They just spend the days like a true space-farer would - floating (or in this case standing) by the water cooler.

 

[Hlynkacg]

Been giving more thought to mass and dimensions.

Rather than try to shield the entire centerfuge with an enormous shadow shield, why not just shield the hab modules at the end? (loitering in the transit tubes would be discouraged)

I whipped a quick mesh together to illustrate



Legend:
Red: Transit tunnel to 0-G portion of spacecraft
Green: Habitable area
Black: Exhaust Deflector/Radiation/Meteor Shield (faces propulsion section)
Blue: Surface mounted Radiator for rejcting heat absorbed by shield.

A quick back-of-the-napkin calculation put the whole assembly at about 45 metric tonnes. Bigelow's published mass for ISS 8x10 Transhab + estimated wheight of shield and 30m tunnel. This puts would the hole spin-section at about 90 tonnes.

What's the call guys? Is this manageable?

---------- Post added at 05:35 AM ---------- Previous post was at 02:39 AM ----------

Upon further consideration, 2 transhab modules is a lot of space for only 5 crewmen. While passengers do change the equation it does raise the question of How much space do we actually need?.

Another issue is what to do with the flywheel?

Is it really neccesary?

I'd like to keep it, as it is an element you don't often see. On the other hand It needs to be fairly massive to couter act the torque of the centerfuge. What can we do to keep it from being dead wheight?

 

[Wishbone]

See this design: http://trajectory.grc.nasa.gov/aboutus/papers/STAIF-2003-177.pdf

 

[mc_]

This puts would the hole spin-section at about 90 tonnes.

Single "Energia" launch :thumbup:

 

[T.Neo]

The problem is the shadow shield to protect against the exhaust, is needed to protect the structure, not the crew. The shield does not have to be particularly heavy, and it is best if it shields the entire habitat/cargo section.

The actual radiation shield, on the other hand... that needs to be pretty heavy and thick. Apart from the main shield to shield the microgravity structure, the cargo, etc, you can have seperate radiaton shields on the centrifuge modules.

Although you will have to reinforce the shield support structure, the centrifuge boom-tunnels, and even the centrifuge modules themselves, it would probably be lighter than an entire seperate, stationary ring attached to the main structure.

Another issue is what to do with the flywheel?

Is it really neccesary?

I'd like to keep it, as it is an element you don't often see. On the other hand It needs to be fairly massive to couter act the torque of the centerfuge. What can we do to keep it from being dead wheight?

I would say, if you don't need it, get rid of it- it just sits there doing nothing, effectively.

Upon further consideration, 2 transhab modules is a lot of space for only 5 crewmen. While passengers do change the equation it does raise the question of How much space do we actually need?.

If you just want to cram people in there, you could probably fit a good number of people in. But the issue is comfort, and somehow I don't think sticking... 60 people in that module for 6 months is going to work out all that well.

 

[Hlynkacg]

...Although you will have to reinforce the shield support structure, the centrifuge boom-tunnels, and even the centrifuge modules themselves, it would probably be lighter than an entire seperate, stationary ring attached to the main structure.

That's what I was thinking.

As for the flywheel I was thinking of using it to house the Hab-section's radiators and tankage but I'm not sure if that will be suffiecient mass. It's largely dependant on the overall size and power requirements of the Crew/Cargo section. If we're hauling colonists (passengers) those requirements will be pretty high. Otherwise it's wasted mass as cargo crates won't complain about the lack of air-conditioning.

...If you just want to cram people in there, you could probably fit a good number of people in. But the issue is comfort, and somehow I don't think sticking... 60 people in that module for 6 months is going to work out all that well.

Well we could sedate them . But it still leaves the question, what kind of passenger capacity are we looking at, and how comfortable do we want them to be?

This in turn will dictate what is needed as far as space and support facilities.

You're initial figure of 450 seems a little high as we still need to haul supplies to feed them and a lander to get them to the surface but lets use that as a starting figure.

 

[T.Neo]

That's what I was thinking.

As for the flywheel I was thinking of using it to house the Hab-section's radiators and tankage but I'm not sure if that will be suffiecient mass. It's largely dependant on the overall size and power requirements of the Crew/Cargo section. If we're hauling colonists (passengers) those requirements will be pretty high. Otherwise it's wasted mass as cargo crates won't complain about the lack of air-conditioning.

That wouldn't make any sense, already piping fluids from the fixed section to the spun section is bad enough, with the flywheel you now want to pump the fluids uphill, transfer the fluids through a moving interface, and then transfer them through another moving interface... it would be better to just have all that stuff on the fixed part of the ship. There's no reason to spin it up.

Well we could sedate them . But it still leaves the question, what kind of passenger capacity are we looking at, and how comfortable do we want them to be?

This in turn will dictate what is needed as far as space and support facilities.

You're initial figure of 450 seems a little high as we still need to haul supplies to feed them and a lander to get them to the surface but lets use that as a starting figure.

Sedating has problems too. You can't sedate someone for 8 months straight and expect the result to be problem-less. For example there will be degeneration issues, maybe nutrition issues as well...

The 450 people is 4 tons per person out of your 1800 ton payload. Food for 1 person for 8 months is something like 700 kilograms. If you could recycle your water efficiently enough, and had a light enough structure, you might be able to pull that off. I assumed that the landers would be shipped there on a different flight, so the vehicle wouldn't have to do everything itself.

Of course you also have to afford storm cellars. Or at least active shielding for normal solar radiation. And maybe you want to include artificial gravity for these people, too, so... maybe 200 people is a better bet.

The accomodations would not be luxurious, of course. But they wouldn't be inhumane.

For example you can have artificial gravity in shifts, for people to exercise in, etc... but then you have space adaptation syndrome problems... maybe that is a better alternative than building one massive centrifuge or having everyone's bones dissolve...

 

[Hlynkacg]

Hmm...

Remove flywheel, add shielding. Looks like its time for another draft.

---------- Post added at 08:03 PM ---------- Previous post was at 12:38 AM ----------

2nd Draft:



Changes:
Added, exhaust deflectors/radiation shields to central Crew/Cargo Module and Centerfuge Habs. Also added Propulsion Section w/ 2000m Tether. Actuall mass and proportions for the Propulsion Section have yet to be determined.

Centerfuge Flywheel has been removed and RCS Module is now attached directly to Centerfuge Hub and Crew/Cargo Module.

Attatchment points for auxillary fuel/water tanks and external payloads are located on the "backside" of the primary deflector/radiation shield to increase it's effective thickness.

The Crew/Cargo Module (Pressurized Payload in the drawing) Is a single massive Transhab. Most of it's interior volume would be comprised of several large tourus-shaped "bays" that can be used to haul pressurized cargo, or configured as bunkrooms when hauling colonists(passengers). The Aft-most bay would be given over to the vessle's Hydroponics Garden and/or food-storage. Each Bay would be airtight in its own right and capable of being sealed in the event of a hull breach. The rigid central hub of the transhab would be heavily reinforced and house the Storm-Shelter, Command Deck, and Airlocks.

I'm still trying to work out the exact volume needed, but for the moment I am assuming a module that is approximately 40m in diameter and 60m long. This is probably overly generous but I figure that it is better to err on the high side then round down.

The centerfuge would house the Galley/Mess Hall, Hygene Facilities(Toilets/Showers), Gymnasium, and accommodations for the 5-man Flight Crew.

By locating the Toilets/Showers, and Serving meals, in the centerfuge we ensure that everyone onboard will spend at least a small amount of time each "day" under gravity. Wether this will be sufficient to prevent muscular degeneration, or cause issues with acclimatization is unknown.

(The storm-shelter would be stocked with a 0-g toilet and traditional "space snacks")

Edit: I just noticed that the RCS thrusters would do not clear the radiation shield, I'll either have to make the booms longer, the shield smaller, or add another set of thrusters to the shield itself.

Radiators and the Communication/Radar Attennas would be mounted either immediatly forward or immediatly aft of the Crew/Cargo Module and centerfuge hub.

 

[T.Neo]

You're gonna need to shield the tunnels that connect the centrifuge modules to the hub.

While thrusting you can just stay in the modules, yes. You don't need radiation shield for the tunnels. I'm talking about the exhaust shield. You can keep the people in the center module or in the centrifuge to shield them from radiation, but those tunnels still need to be shielded against the exhaust flux.

Just make the shield at the front bigger, to encompass the entire centrifuge... it'll look kinda silly, but it'll shield the whole structure more efficiently, and also make shielding the landing craft and/or bulky payloads easier...

Making a segmented transhab would be pretty interesting, I suppose all you need to do is make pressure-resistant and airtight partitions inside the module; there's no major force on them when the whole module is pressurised, if a compartment depressurises then the parition becomes a makeshift wall to the outside. A deflated outer hull would end up being pretty floppy though...

You might want to add a whipple shield, suspended above the main inflated shell by springs... or have individual, inflated compartments that can serve as whipple shields.

 

[Hlynkacg]

While thrusting you can just stay in the modules, yes. You don't need radiation shield for the tunnels. I'm talking about the exhaust shield. You can keep the people in the center module or in the centrifuge to shield them from radiation, but those tunnels still need to be shielded against the exhaust flux.

Just make the shield at the front bigger, to encompass the entire centrifuge... it'll look kinda silly, but it'll shield the whole structure more efficiently, and also make shielding the landing craft and/or bulky payloads easier...

Based on the numbers provided earlier I figured that the exhaust flux was a minimal threat that could be handled simply by reinforcing the structure of the tunnel it's self. The Radiation shielding is much heavier and as a result I see no reason too have more of it then absolutely neccesary.

 

[T.Neo]

Because you're hitting it with... stuff and over time that stuff could have bad effects for a material over time. Some sort of hardened structure is ideal. It doesn't have to be radiation shielding, it doesn't have to be massively heavy, but... just a thin layer of a resistant material would do fine.

And remember that my thermal information discounted sunlight. If you have sunlight and exhaust flux on a structure, that structure could be heated up to beyond its design limit.

 

[jangofett287]

Or worse, Sun to the left of me, Engine exhaust to the right, here I am trying to climb up this damn tube to reach the storm cellar :uhh:

 

[Hlynkacg]

Because you're hitting it with... stuff and over time that stuff could have bad effects for a material over time. Some sort of hardened structure is ideal. It doesn't have to be radiation shielding, it doesn't have to be massively heavy, but... just a thin layer of a resistant material would do fine.

Perhapse a Layer of Mylar foil that can be removed/replaced as part of routine maintenance?

And remember that my thermal information discounted sunlight. If you have sunlight and exhaust flux on a structure, that structure could be heated up to beyond its design limit.

Do you think that we need to add a "rear-facing" shadow shield (that we can point towards the Sun) as per the original ISV?

As a side note, this thread was inspired (in part) by your A real Delta Glider thread.

Perhaps a better title would have been "A real ISV Venture Star".

 

[T.Neo]

Perhapse a Layer of Mylar foil that can be removed/replaced as part of routine maintenance?

Maybe, I was thinking more along the lines of an thin aluminium plate coated in ceramic paint- though I'm not sure what the exhaust effects would be to various materials, that is just a thumb-suck guess.

A rear facing shield won't be able to face toward the sun all the time (often you'll be burning parallel to the Sun, or you might be burning slightly toward the sun.

A dedicated exhaust shield would be a lot like the rear shield on the ISV, except it would be in front of the cargo/passenger/crew section, rather than behind it.

 

[Izack]

A rear facing shield won't be able to face toward the sun all the time (often you'll be burning parallel to the Sun, or you might be burning slightly toward the sun.

Perpendicular, you mean (assuming you meant the Sun's rays)? Aligning parallel would be the one situation where a rear-facing shield would be useful. :tiphat:

I'm liking this thread. This sort of discussion is really interesting to read. I hope this project gets far.

 

[T.Neo]

Perpendicular, you mean (assuming you meant the Sun's rays)? Aligning parallel would be the one situation where a rear-facing shield would be useful.

I did not mean the rays of the Sun, but the direction in which the Sun is in. Same thing, really.

Suffice to say, you could be burning at an attitude where the Sun's rays are hitting the right/left/top/bottom/front side of your ship, in which case a rearward shield probably wouldn't help much.