Deep Space Habitat

GW Johnson · 2016-03-09 10:00:36

It is quite clear that kdb512 and I differ substantially on how best to design a mission. That's OK.

But I think he missed my point about radiation protection entirely. quote: "My calculations say there's no calculating when a SPE is going to hit your spacecraft. Flying in formation behind the active radiation shielding device is about preventing snow days. GCR protection = "go flight". No GCR protection = "no flight". Those are NASA rules, not mine." He seemed to think I was proposing only propellant tanks as radiation protection.

This quote was in response to what I said about using unexpended propellant as "additional radiation protection". Note the word "additional". Baseline (discussed at other times in other threads) is clustering water and wastewater plus fresh or frozen water-bearing food about two places in the vehicle. Those are the flight control station and the sleeping quarters.

15-20 cm water provides all the protection needed to survive in good health a 1972-like 3500 REM solar flare event. Covering those two locations reduces the first year accumulated dose to about 51 REM, during a 60 REM galactic cosmic ray year, even if the solar flare occurs that very same year. The annual limit NASA uses is 50 REM. We don't violate monthly (25 REM) or career limits, either. In my humble opinion the fundamental precision of these limits is less well known than the 1 REM violation.

As for the "dangerous" practice of shedding empty propellant tanks, how is that any different from the staging we have used ever since we flew something beyond a single stage vehicle at all? Answer: it is no different. It is what we already do all the time.

Spacenut: you seem worried by the end-over-end spin. You should not be, it is quite stable. Look at any baton twirler's baton spinning high into the air during the half-time show at any Friday night football game. End-over-end spin is quite stable and controllable. The bias toward spiralling spin about the long axis (like a football) is exactly that: only a bias in thinking. Physics says end-over-end is fine, and in fact the most stable mode of all.

I do share kdb512's trepidations about variable exosphere densities at Mars affecting the outcome of attempted aerobraking. And I think Spacenut was correct to say the flexible or inflatable heat shield materials are one use only.

So, if we choose to attempt aerobraking to conserve propellant, we'd best still bring some extra propellant along for a rocket burn to correct for density error. That won't be for a full delta-vee, but it might be for a quarter or even a third of one. Just a guess. It does reduce somewhat the propellant mass advantage of aerobraking when you plan on having a backup like that.

I do have a cartoon of an 8 rpm deep space hab concept based on two B-330's, a kick stage, and some propellant tanks posted over at http://exrocketman.blogspot.com, in an article about artificial gravity being needed, and how to implement it.

GW

Last edited by GW Johnson (2016-03-09 10:02:51)

kbd512 · 2016-03-09 13:27:54

Rob,

If you're still not happy with SEP for orbital insertions, then let's look at how much additional propellant we need for the MOI burn. TMI dV and MOI dV are inversely proportional, but let's say our 180 day transfer requires a 1km/s to 1.5km/s dV, or thereabouts.

dV Requirement = 1.5km/s

SuperDraco (NTO/MMH)

Isp: 240s
DSH Wet Mass (at LEO): 23t
DSH Dry Mass (at LEO): 12.5t
DSH Dry Mass (at MOI): 11.8t
dV Capability: 1.5km/s

That's well above Falcon Heavy's throw capability.

SEP (Xenon or Iodine):

Isp: 2000s
DSH Wet Mass (LEO): 15t
DSH Dry Mass (LEO): 12.5t
DSH Dry Mass (MOI): 11.8t
dV Capability: 4.7km/s

That's well within Falcon Heavy's throw capability.

Both calculations assume the dry mass of the propulsion hardware is baked into the DSH dry mass.

Edit:

I've pretty much figured out that we can do impulsive burns for both TEI and EOI using storable chemical propellants. That means spiraling in to LMO only reduces our surface stay time by 30 days. I think that's acceptable. I don't know how much ADEPT weighs, but I'm guessing ADEPT + dV for atmospheric corrections puts us at or over our TMI mass limit for a single Falcon Heavy launch. Obviously we could always launch more Falcon Heavies, but at $125M a pop, even those rockets aren't "cheap".

Anyone know if there's an energy efficient way to convert the remaining kerosene and LOX into water?

Last edited by kbd512 (2016-03-09 18:50:25)

RobertDyck · 2016-03-09 13:39:03

Now work it out with aerocapture.

Initially I suggested using a fabric called Nextel 440, because NASA's Ames Research Centre used that for a reusable thermal blanket called Durable Advanced Reusable Surface Insulation (DurAFRSI). It was developed as an upgrade for AFRSI, thermal blanks on Shuttle. Some here argued for carbon fibre instead, noting that ADEPT used carbon fabric. Nextel 440 may not be able to withstand as much heat, but it's definitely reusable. And thermal requirements for aerocapture are not as great as direct entry. ADEPT was developed for direct entry. I'm stull not sure if ADEPT is non-reusble, but if it is then the default is Nextel 440, not propulsive capture.

GW Johnson · 2016-03-09 13:56:34

RobertDyck:

Nextel 440 is very similar to the Nextel 312 I used 3 decades ago in a ceramic composite. It has a solid phase change at about 2300 F, going above which causes brittleness and shrinkage cracks upon cooldown. It comes apart just like a Coleman lantern mantle, and is just as fragile. Meltpoint is far higher at 3300 F. Most alumino-silicate fiber materials have these same limitations.

It should be reusable if the material stays under that phase-change limit. However, when you look at effective gas temperatures at orbital speeds, it is hard to see how one can get braking effect without getting too hot.

Edit: This embrittlement and fragility does not happen until the material is cooled down after heating above the phase change limit. I used it as an infrared "lantern mantle" about the size of a coffee cup, at just about 3000 F. It worked just fine like that in a high-subsonic sliptream for hours at a time. Enough IR to blister your face from 20 feet away (F-100 Super Sabre at full military power), and it would fool a 2-color seeker into believing it was tailpipe steel at only 1200 F. Upon cooldown, the embrittled items would crumble when you picked them up.

GW

Last edited by GW Johnson (2016-03-09 14:33:30)

kbd512 · 2016-03-09 14:05:03

RobertDyck wrote:

Now work it out with aerocapture.
Initially I suggested using a fabric called Nextel 440, because NASA's Ames Research Centre used that for a reusable thermal blanket called Durable Advanced Reusable Surface Insulation (DurAFRSI). It was developed as an upgrade for AFRSI, thermal blanks on Shuttle. Some here argued for carbon fibre instead, noting that ADEPT used carbon fabric. Nextel 440 may not be able to withstand as much heat, but it's definitely reusable. And thermal requirements for aerocapture are not as great as direct entry. ADEPT was developed for direct entry. I'm stull not sure if ADEPT is non-reusble, but if it is then the default is Nextel 440, not propulsive capture.

With a wet mass of 15t, assuming the ADEPT hardware weighs nothing or is baked into the habitat mass, it works. For reasons that I and GW have already stated, even with ADEPT we still need about .5km/s dV capability to correct for atmospheric density variations. If we have no propulsive capability, we better have Mars atmospheric variations down to a science.

I don't think you can count on ADEPT being reusable. I don't think reusability was ever a design consideration.

GW Johnson · 2016-03-09 14:38:07

I don't know what happens to carbon fiber textiles as reentry structures. I thought I saw some data somewhere (maybe on these forums?) that exposure to entry aeroheat would burn off some essential coatings, but not burn away the fiber itself, at least not entirely.

My guess is that there is some ablation, though. And what role those "essential coatings" served is unknown to me. I just remember that they were somehow essential to the functioning of ADEPT.

GW

kbd512 · 2016-03-09 14:59:45

GW Johnson wrote:

I don't know what happens to carbon fiber textiles as reentry structures. I thought I saw some data somewhere (maybe on these forums?) that exposure to entry aeroheat would burn off some essential coatings, but not burn away the fiber itself, at least not entirely.
My guess is that there is some ablation, though. And what role those "essential coatings" served is unknown to me. I just remember that they were somehow essential to the functioning of ADEPT.
GW

How much does it weigh?

SpaceNut · 2016-03-09 19:32:29

Depends on the type...,square footage and thickness....

http://www.fibermaterialsinc.com/catego … -furnaces/
http://www.protechcomposites.com/high-t … er-panels/

kbd512 · 2016-03-11 04:20:09

After reviewing everything I could find about ADEPT, I think aerocapture is right at the edge of technical feasibility with our mass budget and still dangerous. No matter what the final ADEPT solution weighs, it's gonna have to be real light because the heat shield mass is coming out of the mass budget for the DSH if we still need to retain a .5km/s dV capability.

I really hate to lose any days on Mars, given the time and expense of sending humans there in the first place. However, in my opinion the 30 days of surface time lost is not significant. I think integrating SEP into the DSH provides a pretty comfortable dV margin without adding a lot of mass or the engineering problems that the ADEPT solution has to overcome.

In any event, after orbital insertion, the first priority is mating the DSH to the TEI kick stage. The TEI kick stage uses the same SEP hardware that the DSH uses for MOI. I haven't talked much about the TEI kick stage in my mission architecture plans, but I have been looking at the AJ-10-118K. A 15t wet mass TEI kick stage is all we need.

Let's add just a touch of mission architecture to the DSH solution:

DSH + MDV must have a mass of 15t or less, preferably 12.5t or less, for one Falcon Heavy to TMI the stack

MDV obviously transfers the crew to Mars after arrival

MAV obviously transfers the crew to the DSH before departure

DSH + MAV mass is roughly the same as the arrival mass and that's what my TEI calculations are based off of

If the MAV capsule is based on the MDV capsule and stays attached to the DSH for TEI, then the crew can use the capsule to return to Earth. That eliminates another Falcon 9 + Dragon V2 or Falcon Heavy + Dragon V2 flight.

Broader context of a 4 crew member mission:

Launch Opportunity 1:

2 Falcon Heavies to deliver two TEI kick stages to Mars

Launch Opportunity 2:

2 Falcon Heavies to deliver the DSH + MDV

1 Falcon Heavy to deliver Boeing's fancy new active radiation shielding device

1 Falcon 9 to deliver the crew to both DSH's

We're well within NASA's human space flight budget here by using very light DSH's designed for 2 person crews instead of 4 to 6 person crews. If it's desirable to send more crew members, then it's far more feasible to add 2 additional Falcon Heavies to deliver a TEI kick stage and DSH. Without going into details here, I think it's possible to use this DSH solution for Venus and lunar orbital missions. I think we can cover most of our inner solar system human space exploration objectives using 2 person DSH's and swappable mission hardware elements. Obviously some specialized hardware is required for landing on the planets in the inner solar system, but you have to get there first.

kbd512 · 2016-03-11 14:51:16

Previously, GW stated that he wanted to send a BA-330 to Mars. I think a BA-330 would make a superb orbital staging facility and could serve as a habitation backup if there's a problem with our surface habitation solution once we get to Mars. There's enough volume, power, and life support for both crews. The only catch is that to deliver the BA-330 with one Falcon Heavy, we need a real SEP-CTV.

SpaceNut · 2016-03-17 21:46:54

Ignore the title as its about a deep space habitat.... Internal Layout for a Cis-Lunar Habitat

GW Johnson · 2016-03-18 09:58:50

quote: "The only catch is that to deliver the BA-330 with one Falcon Heavy, we need a real SEP-CTV."

That difficulty goes away if we just learn to do on-orbit refueling with cryogenics. The Falcon upper stage that delivers a B-330-based module to orbit is restartable in space. Refuel it from a second launch and use it for a kick stage to Mars. The RP1 is easy, and the LOX isn't too difficult to handle, even with the idiotically-clumsy suits we still use.

Refueling on orbit was how two Saturns would send Apollo to the moon, before they switched to lunar orbit rendezvous with the LM. That was LOX and the far-more-challenging LH2. We just have never bellied-up to the bar and mastered this technology.

But with the easier LOX-RP1, it wouldn't take but maybe 2-3 years' practice near ISS to make it reliable. It'll take longer than that to prove out a proper space suit for Mars or any other surface.

GW

Last edited by GW Johnson (2016-03-18 09:59:25)

SpaceNut · 2016-03-18 19:34:46

If I recall correctly Russia tends to use Kerosene for many a third stage engine so why not. If its good enough for the first stage of the Saturn V then is good enough for other uses....

At some point man must move away from orbital build after lofting the chunks to orbit to one of using resources from space to build what we need just as we did here on earth surface. Sure its going to be hard until we start but that is the problem Nasa is not interested and private industry is just now starting to do but they need to be funded by some one to keep encouraging them to keep going as they do not have the funding sources to do it on there own.

SpaceNut · 2016-03-21 17:33:59

From Minimum Acceptable Net Habitable Volume for Long-Duration Exploration Missions

The proposed volume of 25 m3 is consistent with previously proposed volumes
7 functional areas were identified:
1. Berthing, or sleeping space/private quarters : The volume for each individual crew quarters is 5.4 m3 but ISS crew quarters are, by comparison, 2.1 m3
2. Dining and communal activities : sufficiently large space to simultaneously fit all 6 crewmembers, Includes a window with a portal (~ 0.5 m3) as a way to visually extend the social space and provide an important countermeasure for psychological health.
3. Work space : Sized to allow up to 4 crewmembers to focus on meaningful work or activities simultaneously
4. Exercise (area can also accommodate EVA suit donning and medical care) : Allows for 2 exercise devices to be used concurrently
5. Hygiene : Provide volume for at least 2 separated hygiene and waste compartment areas
6. Translation portals or pass-throughs : Function-thin partitions for visual and acoustic separation, Assumes additional volumes for pass-throughs and transition paths, Adequately sized for a suited crewmember
7. Stowage access : Point-of-use stowage is included in all areas, Assumes crew of 6

I think there is lots of stuff that can take less space than what is given but then again the size of the crew is not 6 but less....

SpaceNut · 2016-03-24 19:30:31

Thanks for creating the venus topic..Tom..
The size, artificial gravity and content of a deep space habitat area all important but we will need to be able to place the unit into a deep sleep for a very long time while the crew are down on the surface and then be able to wake it back up to make use of it for the return trip home...this is something that we have never done....

GW Johnson · 2016-03-25 08:37:13

Spacenut:

We sort-of did the shutdown/storage thing with Skylab between the three crews. Not exactly what you had in mind, I suppose, but sort-of close.

The only problem with that is that all the people who actually did it are now dead or retired. And like I have said before, none of the 50% +/- engineering art was ever written down.

GW

Tom Kalbfus · 2016-03-25 12:42:39

SpaceNut wrote:

Thanks for creating the venus topic..Tom..
The size, artificial gravity and content of a deep space habitat area all important but we will need to be able to place the unit into a deep sleep for a very long time while the crew are down on the surface and then be able to wake it back up to make use of it for the return trip home...this is something that we have never done....

Somehow, when I hear the term "Deep Space Habitat" I don't think of the ISS or Skylab or any other tin can in space where people work. A habitat is a home, and so far, no one actually lives there. People stay there for months at a time, and even a multi-year manned Mars Mission, doesn't constitute crew members actually living on the spaceship and calling it home. They most likely leave family members behind and they look forward to being reunited with them at the end. For that reason ISS is not home, nor any interplanetary vessel designed to bring crewmembers to Mars and back, it is a place for them to live, to eat, sleep and do scientific experiments, but it is not their home! A habitat is a home, it is a place where people grow up, go to school.

SpaceNut · 2016-03-25 21:17:21

Even with the commercial industry Bigelow inflateable going to the station there are still no people going there except for space nations and the rich, when will there be others to live and make space stuff for the future of man.....

Tom Kalbfus · 2016-03-26 01:11:38

Space technology is still inefficient. One should be able to go into space without that being a news story in and of itself.

kbd512 · 2016-03-26 20:44:56

Tom Kalbfus wrote:

Space technology is still inefficient. One should be able to go into space without that being a news story in and of itself.

The only way to make that technology more efficient is to spend time and money on its development. I'm not quite sure what it is that you expect, but I think our space-related technology is pretty efficient these days. Our energy storage, power production, and rocket engine technologies have all come quite a ways since the days of Apollo.

We don't have Star Trek level technology and probably won't within our lifetimes, but the only way to eventually reach that level of technological sophistication is to continually develop, test, and use new technologies. I think we're doing that already.

SpaceNut · 2016-03-26 21:07:55

Yup no star trek techology required only bodies that are more common than the astronaut core..... We currently have a total of just 6 onboard the ISS and only temporarily 9 for short periods of time and only when the Chinese have there station manned is there ever more in orbit....Isn't it time that we have lots more than that.....

RobertDyck · 2016-03-26 21:30:25

kbd512 wrote:

We don't have Star Trek level technology and probably won't within our lifetimes

Aww! But it's so easy! Producers for Star Trek had to film early episodes, but the set for their shuttle craft wasn't ready yet. So they took props from the movie "Forbidden Planet", specifically decelerator platforms, turned them upside-down and called them "transporter platforms". They then used a cheap special effect: actors stand on the platforms, cut camera, put TV static where the actors were, then cut to actors standing on the back lot that's supposed to be an alien planet. No explanation how it's supposed to work. Isn't that easy?
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kbd512 · 2016-03-26 22:25:43

GW Johnson wrote:

quote: "The only catch is that to deliver the BA-330 with one Falcon Heavy, we need a real SEP-CTV."
That difficulty goes away if we just learn to do on-orbit refueling with cryogenics. The Falcon upper stage that delivers a B-330-based module to orbit is restartable in space. Refuel it from a second launch and use it for a kick stage to Mars. The RP1 is easy, and the LOX isn't too difficult to handle, even with the idiotically-clumsy suits we still use.
Refueling on orbit was how two Saturns would send Apollo to the moon, before they switched to lunar orbit rendezvous with the LM. That was LOX and the far-more-challenging LH2. We just have never bellied-up to the bar and mastered this technology.
But with the easier LOX-RP1, it wouldn't take but maybe 2-3 years' practice near ISS to make it reliable. It'll take longer than that to prove out a proper space suit for Mars or any other surface.
GW

What method of delivery for a DSH or Mars Orbital Station (MOS) requires more mass, a SEP powered tug or orbital refueling stations that store cryogenic chemical propellants?

Apart from attaining orbit or orbital transfers, I can't think of any all-chemical architecture that has reasonable mass requirements.

The development of SEP for the DSH and CTV has three primary benefits:

1. Far more payload delivered for equivalent propulsion mass

2. Capability to deliver all required deep space transit and surface exploration hardware components without super heavy lift

3. Additional power availability for DSH and MOS to provide life support and active radiation shielding functions

Sidebar thoughts on why MOS is a good idea:

For simplicity's sake, the DSH is not intended to do anything other than support two crew members for 1000 days. It's a miniature space station and nothing more. Without a chemical kick stage attached for return, the DSH is effectively a one way transit vehicle. If something in the DSH or MDV fails along the way or the kick stage can't be mated or is not usable, assuming the crew survives long enough to reach Mars, then the crew can use MOS as a repair facility. Both DSH can dock with MOS after arrival, the crew can inspect and repair the DSH or MDV, as required, and continue on with their mission.

The DSH's transit to Mars in pairs to reduce the probability of a single event irreparably damaging the only habitable vehicle that the astronauts have to use. NASA's mission architectures always deliver the crew in a single DSH. The whole notion of "safety in numbers" only applies when everyone in the group isn't subjected to the same event. Putting every crew member in a single vehicle will only ensure that the vehicle has to be ridiculously over-engineered to meet the required level of reliability.

NASA also attaches a contingency consumables module to the DSH that is intended to provide rations for the crew in the event that landing on Mars is not possible. My take on this is that the contingency consumables should be stored in MOS. If something prevents the crew from descending to the surface, such as a MDV that's damaged beyond repair, then the crew can still tough it out at MOS until the next departure window using contingency consumables stored in MOS.

Tom Kalbfus · 2016-03-27 08:24:22

kbd512 wrote:

Tom Kalbfus wrote:
Space technology is still inefficient. One should be able to go into space without that being a news story in and of itself.
The only way to make that technology more efficient is to spend time and money on its development. I'm not quite sure what it is that you expect, but I think our space-related technology is pretty efficient these days. Our energy storage, power production, and rocket engine technologies have all come quite a ways since the days of Apollo.
We don't have Star Trek level technology and probably won't within our lifetimes, but the only way to eventually reach that level of technological sophistication is to continually develop, test, and use new technologies. I think we're doing that already.

Have you been in space lately? I would consider space travel to be efficient if somebody you know went into outer space. Nothing much really, just a short jaunt into orbit and back. The dawn of the space age was in 1957, the dawn of the aviation age was in 1903, it is now 2016, this would be the equivalent of 1962 for the aviation age. I've sure if someone in 1962 got into an airplane and flew from New York to Chicago, it wouldn't have made the headlines. In 1962, Presidents flew in airplanes, so who was the last US President to travel into space? The real question is why has our progress in space travel been so crippled? And I'm talking about the east stuff, just going into orbit, not going to Mars or anything like that!

Last edited by Tom Kalbfus (2016-03-27 08:25:50)

SpaceNut · 2016-03-27 09:29:53

kbd512 wrote:

, What method of delivery for a DSH or Mars Orbital Station (MOS) requires more mass, a SEP powered tug or orbital refueling stations that store cryogenic chemical propellants?

IEEE 2014 Space Launch System Upper Stage Technology Assessment

Launch Vehicles and Earth Departure Stages

http://images.spaceref.com/fiso/2015/05 … -20-15.pdf

So what is the exact size of the chemical kick stage?
Which pieces need them?
Which pieces need just the SEP and Which ones need both?

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