Author Topic: Sea Dragon class LV thead  (Read 82607 times)

Offline tnphysics

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Sea Dragon class LV thead
« on: 09/07/2007 04:31 AM »
What are your suggestions on 440+ tons to LEO LVs?

My favorite would be Sea Dragon built out of aluminum. What would its payload be?

And why does Sea Dragon-2 have only 320 Isp? That sounds too low for even a pressure-fed oxyhydrogen engine.

The application would be manned Mars missions (about 1200 tons IMLEO, 500 tons of which is radiation shielding against cosmic rays, using NTP for TMI).

Offline Kaputnik

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Re: Sea Dragon class LV thead
« Reply #1 on: 09/07/2007 08:15 AM »
There's no need for 400mt+ boosters. It would be much better to develop a smaller booster suitable for lunar missions which can then fly three to five times to build up a Mars mission.
Your IMLEO estimates are far too high, IMHO. A Mars mission can be done for under 500t total.
Waiting for joy and raptor

Offline halkey

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Re: Sea Dragon class LV thead
« Reply #2 on: 09/07/2007 09:11 AM »
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Kaputnik - 7/9/2007  3:15 AM

There's no need for 400mt+ boosters. It would be much better to develop a smaller booster suitable for lunar missions which can then fly three to five times to build up a Mars mission.
Your IMLEO estimates are far too high, IMHO. A Mars mission can be done for under 500t total.

I disagree about a smaller booster being better for lunar missions.  If the USA plans to install a permanent outpost on the moon that's more than just a tent with some guys camping in it, a large booster like the Sea Dragon could prove immensely valuable.   And it'd prove valuable also if you plan to send multiple missions to Mars.  People seem to believe that it's better to have a lot of little launches than one big launch, but I doubt if that's always a good strategy.  Just launch a big booster from the ocean and be done with it!

Offline rumble

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Re: Sea Dragon class LV thead
« Reply #3 on: 09/07/2007 12:56 PM »
My question is from a slightly different angle.

It seems we have a history of building "right-sized" rockets, that then suffer weight increases and/or performance shortfalls, then we have to optimize the crap out of them to get the job done.

Is a really big, dumb booster more expensive than all the effort expended on optimization & advanced materials?

Is there harm in overkill?  Granted, if we tried to build something with 30 F-1 engines, now we're hit with high engine expense, and duplicated complexity.  But, for example, a sea dragon is a single enormous 1st stage engine.  Nobody would win awards for efficient design, but it would give us tremendous capacity to put virtually anything into space.

Maybe something the size of a sea dragon is out of the question, since launch rates would be so low (the rarity of having a payload in this mass range).  But for that matter, we don't have payloads that large because we can't.  If an oversized launcher was available, how much cheaper could spacecraft be built?  If weight weren't much of an issue, how much would that change design considerations?  Redundancy?  Safety?

How fast could one fill a massive propellant depot if a sea dragon were available?

At one point in time, I thought we didn't make massive rockets because we couldn't.  Now I realize it's just because we never think ahead like that.  I know it's not easy to make things scale like that (whole new worlds of combustion instability, etc), but it would be an effort worth while, IMHO.

Matt

Offline kkattula

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Re: Sea Dragon class LV thead
« Reply #4 on: 09/07/2007 04:10 PM »
Quote
Kaputnik - 7/9/2007  7:15 PM

There's no need for 400mt+ boosters. It would be much better to develop a smaller booster suitable for lunar missions which can then fly three to five times to build up a Mars mission.
Your IMLEO estimates are far too high, IMHO. A Mars mission can be done for under 500t total.

Ask Richard P. Speck of Micro-Space. He thinks he can put 1 man (or 2 petite women) on Mars using one Falcon 9. Not a heavy either, just a regular.

Offline tnphysics

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Re: Sea Dragon class LV thead
« Reply #5 on: 09/07/2007 08:53 PM »
How?

Offline rumble

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Re: Sea Dragon class LV thead
« Reply #6 on: 09/07/2007 11:06 PM »
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kkattula - 7/9/2007  11:10 AM

Quote
Kaputnik - 7/9/2007  7:15 PM

There's no need for 400mt+ boosters. It would be much better to develop a smaller booster suitable for lunar missions which can then fly three to five times to build up a Mars mission.
Your IMLEO estimates are far too high, IMHO. A Mars mission can be done for under 500t total.

Ask Richard P. Speck of Micro-Space. He thinks he can put 1 man (or 2 petite women) on Mars using one Falcon 9. Not a heavy either, just a regular.
Does the passenger survive in this plan?

Offline meiza

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Re: Sea Dragon class LV thead
« Reply #7 on: 09/07/2007 11:08 PM »
Quote
How?
Use the search function, have some effort yourself.

Offline MKremer

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Re: Sea Dragon class LV thead
« Reply #8 on: 09/07/2007 11:35 PM »
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tnphysics - 7/9/2007  3:53 PM

How?

Click the Search button on the top menu. Type in Speck. Click the Search All Posts button. Start browsing.

Just how long do you expect folks here to do all the research work for you just so you can easily click on a single link or two? Quit asking obvious questions that you can easily search for the answers yourself.
 :angry:

Offline tnphysics

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Re: Sea Dragon class LV thead
« Reply #9 on: 09/08/2007 02:34 PM »

Sorry.

   You must surround the entire living quarters with shielding that has the same effectiveness as five feet of water in a tank. This requirement should be used for all mass calculations for extremely long duration missions. Lighter elements are more effective per unit mass, so using liquid hydrogen gives the lightest shield. A thin layer of boron-10 would be needed as a neutron absorber.
 
    It is not possible to get away with less shielding, owing to the fact that the incoming cosmic rays have enough energy to create electron-positron pairs. These pairs are called secondary radiation, and they, too, must be stopped. However, these, in turn, create more electron-positron pairs until their energy drops below 1.1 MeV (the minimum energy needed to create an electron-positron pair) (At some point, each positron will annihilate an electron, producing two gamma rays). Because, for a given total energy of ionizing radiation, alpha radiation is more damaging than beta radiation which is more damaging than gamma rays, and lower frequency (longer wavelength) gammas are more damaging than shorter wavelength gammas, a thinner shield would actually be counterproductive, so far as cosmic rays are concerned.

 


Offline Kaputnik

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Re: Sea Dragon class LV thead
« Reply #10 on: 09/08/2007 04:23 PM »
I'm not an expert on this, but what's the difference in radiation exposure between LEO and the Earth-Mars interplanetary space? I like to believe that Zubrin got it right when he calculated that radiation wouldn't be a show-stopper for a Mars mission.
Waiting for joy and raptor

Offline kkattula

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Re: Sea Dragon class LV thead
« Reply #11 on: 09/08/2007 05:27 PM »
Basically, if you take a bunch of smokers, send them to Mars and back over 3 years, (without cigarettes), their life expectancy on return would be higher than if they'd stayed on Earth and continued smoking.

Offline kkattula

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Re: Sea Dragon class LV thead
« Reply #12 on: 09/08/2007 05:45 PM »
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tnphysics - 9/9/2007  1:34 AM

Sorry.

   You must surround the entire living quarters with shielding that has the same effectiveness as five feet of water in a tank. This requirement should be used for all mass calculations for extremely long duration missions. Lighter elements are more effective per unit mass, so using liquid hydrogen gives the lightest shield. A thin layer of boron-10 would be needed as a neutron absorber.
 
    It is not possible to get away with less shielding, owing to the fact that the incoming cosmic rays have enough energy to create electron-positron pairs. These pairs are called secondary radiation, and they, too, must be stopped. However, these, in turn, create more electron-positron pairs until their energy drops below 1.1 MeV (the minimum energy needed to create an electron-positron pair) (At some point, each positron will annihilate an electron, producing two gamma rays). Because, for a given total energy of ionizing radiation, alpha radiation is more damaging than beta radiation which is more damaging than gamma rays, and lower frequency (longer wavelength) gammas are more damaging than shorter wavelength gammas, a thinner shield would actually be counterproductive, so far as cosmic rays are concerned.

 


I think you've got a lot of this wrong. 5 feet of water is only needed in an emergency shelter for solar flares.  Alpha radiation can be stopped by tissue paper, and is next to harmless, unless an emitter is ingested or inhaled. Higher frequency gammas are much more damaging than lower.

Cosmic ray exposure over a 3 year mission with minimal shielding would only approach the carreer safe limit.

Offline tnphysics

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Re: Sea Dragon class LV thead
« Reply #13 on: 09/08/2007 10:48 PM »
Cosmic rays may be more damaging.

Offline Christine

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Re: Sea Dragon class LV thead
« Reply #14 on: 09/10/2007 06:50 AM »
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Kaputnik - 8/9/2007  11:23 AM
I'm not an expert on this, but what's the difference in radiation exposure between LEO and the Earth-Mars interplanetary space?

The flux of solar protons drops off at the inverse square of distance from the sun. At mars, you'd be looking at ~40% of the exposure at earth outside the Van Allen belt. In LEO the belt shields those on ISS from almost all solar protons.  Galactic cosmic rays are much more energetic and pretty much the only thing that will shield from them is a 30km stratosphere or 10m+ of lead. Fortunately the flux is pretty low. Considering what else could go wrong on a mars trip, risking a 10% increase in your lifetime incidence of cancer would be the least of your worries.

The best way to shield from solar protons during a flare in my mind would be to put a giant water filled polyethylene tank on the sun-facing side of your habitat.

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