Author Topic: DIRECT Applications Program - Mars & NEO Technologies  (Read 27629 times)

Offline mmeijeri

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Re: DIRECT Applications Program - Mars & NEO Technologies
« Reply #20 on: 02/02/2009 03:08 pm »
I'm not sure if I should be mentioning this or not, but some recent discussions we were involved in with representatives from ESA have created a very interesting notion:   ESA wants to extend the lifespan of ISS beyond the current 2016 "sell by date".   They want to build their own Upgrade Module which would allow them to do so.   Only snag is that they really need an HLLV to lift such a heavy module.

Very interesting. I haven't seen that in the ESA architecture document, so you may well have said something that isn't public knowledge yet ;) On the other hand, the ESA website is very difficult to navigate, so maybe the information is public yet impossible to find. According to this flyer http://esamultimedia.esa.int/docs/MinisterialCouncil/MC-ISSEVOLUTION_1811.pdf ESA wanted to get funding for an experimental life support system, I don't know if they got it. It has a very interesting name by the way: Ares  :)
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Offline kraisee

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Re: DIRECT Applications Program - Mars & NEO Technologies
« Reply #21 on: 02/02/2009 03:13 pm »
My understanding is they're simply in the 'thinking about it' phase and are looking around for a good idea of what missions the tech could support.   I don't think it's anywhere close to being integrated into their official architecture yet.   Apart from anything else, I don't think they have a launcher on the horizon which could support it -- which is why they were so interested in Jupiter-120/232.

Ross.
« Last Edit: 02/02/2009 03:14 pm by kraisee »
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Offline Lars_J

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Re: DIRECT Applications Program - Mars & NEO Technologies
« Reply #22 on: 02/02/2009 03:36 pm »
One area that, AFAIK, is mission critical but gets surprisingly little public recognition is the matter of radiation shielding.  Once the vehicle is outside the Earth's magnetosphere, it will be flying through the solar wind (basically high-energy alpha- beta- and gamma-radiation) as well as some of the more exotic creatures in the form of cosmic rays, which might be travelling at near-c.

That was part of the genius behind the TransHab concept... It had a central safe area shielded by water.

Of course such a design hasn't flown, so who knows how well it would work. But it seemed well thought out.

Offline kraisee

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Re: DIRECT Applications Program - Mars & NEO Technologies
« Reply #23 on: 02/02/2009 04:03 pm »
Lars,
   I've liked that idea for a long while.   They're going to need water supplies anyway, even using recycling systems.   Putting that mass to good use as a rad shield is very sensible IMHO.

   Of course to ensure it doesn't freeze/boil, it would need to be kept inside the pressure vessel, not outside.



   A totally different use for water as a protection system which I liked is also theoretically possible.   It requires copious amounts of fuel/power for the propulsion system, so is not very efficient, but it would offer very high MMOD protection levels.   Essentially it would make the shell of the entire vessel from Pykrete -- a mixture of wood pulp and hardened ice.   A modern-day equivalent probably wouldn't use wood pulp of course, but you get the general idea.   It would essentially be the in-space equivalent of the WW-II 'iceberg' aircraft carrier; "The Habakkuk".   But as I say, I don't even want to think about how much fuel you would need to have to send such a massive thing anywhere around the solar system...

Ross.
« Last Edit: 02/02/2009 04:04 pm by kraisee »
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Offline mmeijeri

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Re: DIRECT Applications Program - Mars & NEO Technologies
« Reply #24 on: 02/02/2009 04:14 pm »
LLO and a NEO have been mentioned as precursor missions to a Mars mission. I would suggest considering a GEO station, which could be moved to L1/LLO eventually. While the delta v is actually a bit higher than to LLO, the travel time is shorter, which sounds good from a safety point of view. Also, high bandwidth, low latency communications are probably also easier than at L1 or in LLO or even LEO. And because GEO is outside the van Allen belts, you would have to deal with cosmic radiation and SPE just as you would with an L1/LLO station or a Mars crew transport craft, providing a proving ground for radiation protection technologies.
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Offline kraisee

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Re: DIRECT Applications Program - Mars & NEO Technologies
« Reply #25 on: 02/02/2009 04:19 pm »
Problem with a GEO station is that none of the EELV-class launchers could send a descent-sized spacecraft (supplies or crew) there.

You would limit the entire system to being supported by the Jupiter's alone and instantly make it completely impossible for Russia, Europe, Japan or any other partners to have any involvement at all.

We don't want to do that.

We want a system whereby the International partners can realistically contribute, and where domestically the Atlas, Delta, Falcon, Taurus and whoever else develops the capabilities are all be able to provide significant quantities of supplies and/or crew to the station.   And that means staging in LEO.

Ross.
« Last Edit: 02/02/2009 04:20 pm by kraisee »
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Offline mmeijeri

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Re: DIRECT Applications Program - Mars & NEO Technologies
« Reply #26 on: 02/02/2009 04:45 pm »
We want a system whereby the International partners can realistically contribute, and where domestically the Atlas, Delta, Falcon, Taurus and whoever else develops the capabilities are all be able to provide significant quantities of supplies and/or crew to the station.   And that means staging in LEO.

Yes, in the short/medium term. But before you're ready to do a LLO precursor mission, many years from now, it might be a consideration.
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Offline kraisee

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Re: DIRECT Applications Program - Mars & NEO Technologies
« Reply #27 on: 02/02/2009 05:00 pm »
We want a system whereby the International partners can realistically contribute, and where domestically the Atlas, Delta, Falcon, Taurus and whoever else develops the capabilities are all be able to provide significant quantities of supplies and/or crew to the station.   And that means staging in LEO.

Yes, in the short/medium term. But before you're ready to do a LLO precursor mission, many years from now, it might be a consideration.

I think there's a potential for an HEO/GEO station for something like routine transfer between Mars and Earth, but it seems to add an extra layer of complexity for the Lunar phase and I just don't see how that actually pays off.   If all the partners had bigger launchers as well, then I could see something of the sort (although even in that scenario the LEO option would be improved considerably also).

Without doubt though, I am already convinced that there is a strong case to be made for a staging area at EML-2 at some point in the future.   There are lots of clear and unique advantages to be had from there.

Ross.
« Last Edit: 02/02/2009 05:02 pm by kraisee »
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Offline Kaputnik

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Re: DIRECT Applications Program - Mars & NEO Technologies
« Reply #28 on: 02/03/2009 11:51 am »
One area that, AFAIK, is mission critical but gets surprisingly little public recognition is the matter of radiation shielding.  Once the vehicle is outside the Earth's magnetosphere, it will be flying through the solar wind (basically high-energy alpha- beta- and gamma-radiation) as well as some of the more exotic creatures in the form of cosmic rays, which might be travelling at near-c. 

There has to be a reasonable attempt to mitigate the total dosage that the crew experiences during the mission (I've seen estimates as high as 900 days as a Mars flight duration - remember that Mars has no magnetic field, so astronauts on the surface would still need protection from solar flares). 

I've seen that some work has been done on active electromagnetic sheaths for protecting manned spacecraft, but I bet that they are power-hungry.  What is the current state-of-the art for passive (structural) shielding?

Attention would also need to be given to designing a 'storm shelter' in the crew vehicle to increase survival probability against a solar flare.  I've read that an armoured 'box' of lead, gold foil and a water-filled cavity might do the job.  It also occurs to me that the spacecraft might be within the radiation stream for several days, so the shelter would need basic life-support such as liquid water, atmospheric recycling and basic waste management.

Additionally, the shelter would need duplicate flight controls.  We cannot presume that the flare would happen during interplanetary coast or a parking orbit, so it must be possible to execute burns and other manoeuvres from within the shelter.
Re: radiation shielding

Obviously this is a concern, both in terms of background cosmic radiation and solar flares, and all reasonable attempts should be made to mitigate the effects.
From what I have read, a layer of polythene makes a better barrier than lead, because it converts the radiation into less harmful products. In fact, anything with lots of hydrogen in it is apparently good- hence water shielding. I have also read that NASA reccomend a barrier density equal to about a ten centimetre layer of water (sorry, I cannot find the source for this).

My main point, though, would be that we should stop thinking about dedicated 'storm shelters' with 'backup' systems on board, from where the crew can operate the ship. That is unnecessary duplication and a waste of mass. Instead, I think we should make a crew dormitory (or cluster of private cabins) which is shielded, with basic hygeine facilities included in the shielded area. The crew would spend their sleep and rest periods, perhaps half of every day, in this area, where they would be protected from cosmic radiation, and in periods of solar activity would be instructed not to move from that area. The non-shielded areas of the ship could include storage space, leisure facilties, a the gym, and the crew would have a strict rota limiting the length of time they spent in these areas.

A two-year supply of fresh drinking water for a four person crew amounts to 5840kg, which according to my calculations is enough to provide a 10cm shield around a cylinder measuring about 3m long and 4m diameter- not a big volume, but about enough to provide basic sleeping quarters plus a toilet.

On the Martian surface, the habitat module could be protected using sandbags filled with regolith, or with soil bulldozed against it by a roving vehicle. The crew working on the surface in EMUs would clearly be at higher risk, but due to issues like dust abrasion limiting nthe suits' lifespans, this sort of activity would be limted anyway. It would be very valuable if the pressurised rover could incorporate a degree of shielding, allowing the crew to make long sorties away from the hab.
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Offline mmeijeri

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Re: DIRECT Applications Program - Mars & NEO Technologies
« Reply #29 on: 02/03/2009 12:11 pm »
I think there's a potential for an HEO/GEO station for something like routine transfer between Mars and Earth, but it seems to add an extra layer of complexity for the Lunar phase and I just don't see how that actually pays off.

I agree, not as a permanent part of an infrastructure for travel to and from the moon. But people suggested a LLO station as a proving ground for Mars technology. I think it would be easier and safer to do that in GEO (and before that in LEO) than in LLO. Once you got the technology up and running you wouldn't need a GEO station anymore (unless for tourism) and you could move the whole station to L1/LLO by SEP.

And even for the Moon, a GEO testing phase (preceded by a LEO assembly and testing phase) might make sense for ESA since they are planning for a LLO station anyway. Easier to test it out in GEO, then move it to LLO with SEP.

Quote
Without doubt though, I am already convinced that there is a strong case to be made for a staging area at EML-2 at some point in the future.   There are lots of clear and unique advantages to be had from there.

L2 has a delta v advantage over L1, but it also has a longer travel time. Incidentally, Farquhar advocated an L2 station that could double as a communications node a long, long time ago.
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Offline mmeijeri

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Re: DIRECT Applications Program - Mars & NEO Technologies
« Reply #30 on: 02/03/2009 12:19 pm »
From what I have read, a layer of polythene makes a better barrier than lead, because it converts the radiation into less harmful products. In fact, anything with lots of hydrogen in it is apparently good- hence water shielding. I have also read that NASA reccomend a barrier density equal to about a ten centimetre layer of water (sorry, I cannot find the source for this).

There are tons of papers on radiation shielding, it is a major problem for both Mars and long term Moon missions. It is a multidisciplinary field, with interesting links to cancer research, nuclear technology, cell biology.

A good overview is given in http://www.nap.edu/catalog/12045.html
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Offline A_M_Swallow

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Re: DIRECT Applications Program - Mars & NEO Technologies
« Reply #31 on: 02/08/2009 10:44 pm »
Ben,
   We have been investigating the options which a Methane propulsion system would create.

   Obviously, its a great technology to have for returning from a Mars mission where the Methane can be extracted from the Martian atmosphere via fairly straight-forward ISRU technologies.

   But we've been looking at what effect it would have if we applied it to the Lunar architecture first, as a testbed.

   The numbers indicate that an LSAM Descent Stage the same physical size as the current one, but powered by LOX/CH4 instead of LOX/LH2, would offer significantly greater payload mass to the Lunar surface.   It's a potentially massive upgrade to the system if we were to implement it.   We could potentially start delivering useful payload modules to the Lunar surface massing over 35mT -- even more if we could fill the LSAM's LOX tanks at an LEO Depot too.
{snip}

If 6 month missions are performed on the Moon and Mars the mass of the zero boil off hardware or the extra hydrogen or both has to be allowed for.  LOX/LH2 engines are not as good as they look.

Offline Ben the Space Brit

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Re: DIRECT Applications Program - Mars & NEO Technologies
« Reply #32 on: 02/13/2009 10:40 am »
Here's an idea: A Solar System Grand Tour Vehicle (GTV).

The vehicle is basically a multiply-reusable MTV.  First you have a habitat module (either a true MTV or a modified ISS-2 module as discussed over on the ISS-2 thread).  This will also include some general-purpose sensors for navigation, collision avoidance, etc.  Attach a propulsion module to that - perhaps a LCH4 EDS of the type Ross has mentioned before and also a multiply-reusable inflatable balute for aerobraking. 

This vehicle is designed to be adaptable for any number of missions.  Forward of the MTV hab/command module would be a mission module that would be launched specially for every mission (including specialised sensors).  For example, a Venus orbiter would have racks of balloon probes and optimised-lifespan surface sampler probes.  A Mars pathfinder would have remote-control rovers to allow real-time surface survey and, possibly, a solar-powered aircraft of some kind (probably an airship - Mars' thin atmosphere would make aerodynamic lift surfaces of debatable value).  Ultimately, of course, it would serve as the orbit-to-orbit tug for the Mars Surface Habitat Lander.

This mission scheme would require pre-positioning of resources in some cases - mostly JUS/depot tankers at the destination planet to fuel up for the breakaway burn.

Thanks to Mir and ISS we now have experience in refurbishing manned modules to increase their lifespan so that they could function for about a decade.  Given the proposed length of some Mars missions, the hab module could serve up to three missions, IMHO.  I would expect that the aerobreaking shield and the propulsion units would need to be replaced for every flight as (naturally) would the mission module.  However, even if only the hab unit with main power and general-purpose sensor pallets are reusable, it would still save some cash in the long run.

Now, onto the reason for the name: A "Grand Tour" mission

The vehicle leaves Earth and flies to Venus, aerobraking into orbit.  There, the GTV rendezvouses with Tanker A, which also is carrying the mission module for the Venus orbital mission.  The ship remains in orbit, the crew carrying out telepresence surveys of the atmosphere and surface until the next Mars transfer orbit window opens.  The vehicle then expends the Venus Mission Module and inserts into a transfer orbit.

Upon arrival at Mars (once again using aerobraking), the ship then will use the Mars Mission Module (which it has carried since Earth Departure).  As well as rovers and blimp probes for Mars surface survey, it will also carry racks of penetrometers and other survey equipment to use on the Martian moons.  The ship will rendezvous with Tanker B, which will also have a logistics module to 'top up' any supplies - The GTV will have enough supplies for the entire mission but the logistics module will provide a safety net as well as topping up on 'luxury' consumables like condiments.

When the next available Earth return window opens, the GTV will head off home.  Earth Orbit Insertion will be by aerobraking again. 

During mission planning, all transfer orbits will be carefully analysed for potential asteroid encounters.  Unused penetrometers intended for the Deimos and Phobos missions could used to sample such objects.  If the orbits and fuel situation are especially favorable, the vehicle could even rendezvous with an NEO and spend some time surveying it using the sensors designed for use on the Martian moons (as they have many similarities to most asteroids).

Once the mission crew is home, a J-120/Orion service crew will arive (with an MPLM full of parts and spares) to refurbish the hab module.  A new propulsion module will be sent up by J-232.  This will be periodically used to maintain the orbit against atmospheric drag and it will be fully fuelled before any further missions.

Total Launch Requirements
Habitat/Command module - J-232 CaLV
Propulsion module - J-232 CaLV
CEV and Mission Module - dual-manifest J-232
Tanker/Logistics Module - J-232 CaLV with orbital refuelling post-launch

Of course, after the first mission, you save one launch per mission by reusing the Hab/Command module
« Last Edit: 02/13/2009 11:18 am by Ben the Space Brit »
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Offline ANTIcarrot

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Re: DIRECT Applications Program - Mars & NEO Technologies
« Reply #33 on: 02/19/2009 05:22 pm »
Why just use the jupiter rocket as a way of getting out of Earth orbit? The size and weight of the payloads it can carry mean there are new possibilities inside the Van Allan belts as well as outside of them.

*SSTO research. Put a DC-X-II on top, (or your choice of exotica) launch it into orbit and see it it can deorbit, restart its engines, and land. Engine restart after reentry and/or exotic TPS is not something we can easily test on the ground. And even when we can, there are always kill joys who don't accept the results. "Oh, but in space it's different!" A science experiment like this might be a low cost and low risk way of getting the practical experience needed to solve such problems. Or at least cheaper than a DC-Y or X-33 that can do the test all by itself.

*Nuclear safety. An Atlas or Delta can launch a nuclear reactor or propulsion system into orbit, but the 232 could launch it into orbit wrapped up in some 60 tons of crash safety equipment. That might mitigate some of the saner critics of nukes in space.

*Practical test of satellite weight VS cost. The theory goes if satellites weighed twice as much they would cost one third as much. Challenge colleges to build a functional satellite without using aerospace materials or technologies. "Can you build sputnik from Radio Shack parts? If so what else?" Set some minimum requirements and a price cap. Be more of a publicity stunt than anything of real use, but that might not be a bad thing. And on most launches a 120 will have mass to spare.

*SSP demonstrator. Space Solar Power advocates need a simple compact power source to validate their microwave transmitter and electric-propulsion concepts. NASA wants at some point in the future to launch nukes. Direct is pretty much the safest way to do the latter. Say...

*Military applications. A 6m IR telescope in 500km equatorial orbit can (theoretically) track a 10m+ object at the 45th parallels; especially if it is carrying a pair of F119 engines. Having spent so much money on stealth, the military might want to know how easily other space powers can break it. Or any number of other harebrained schemes none of us are cleared to know about.

Sure most of this can be done with existing launchers, but the 120's throw capacity makes it that much easier.

Offline Kaputnik

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Re: DIRECT Applications Program - Mars & NEO Technologies
« Reply #34 on: 02/19/2009 07:37 pm »
Why just use the jupiter rocket as a way of getting out of Earth orbit? The size and weight of the payloads it can carry mean there are new possibilities inside the Van Allan belts as well as outside of them.

Umm, didn't you read the thread title?
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Offline mmeijeri

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Re: DIRECT Applications Program - Mars & NEO Technologies
« Reply #35 on: 02/25/2009 08:22 am »
   The numbers indicate that an LSAM Descent Stage the same physical size as the current one, but powered by LOX/CH4 instead of LOX/LH2, would offer significantly greater payload mass to the Lunar surface.

Can you say more about this? Is it because you have less boil-off / need less insulation with methane?
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Offline Kaputnik

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Re: DIRECT Applications Program - Mars & NEO Technologies
« Reply #36 on: 02/25/2009 12:59 pm »
   The numbers indicate that an LSAM Descent Stage the same physical size as the current one, but powered by LOX/CH4 instead of LOX/LH2, would offer significantly greater payload mass to the Lunar surface.

Can you say more about this? Is it because you have less boil-off / need less insulation with methane?


He said physical size, not mass. CH4 is considerably denser than LH2, more than enough to offset its lower isp. The lander would end up heavier, and higher performance, but be the same size.
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Offline mmeijeri

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Re: DIRECT Applications Program - Mars & NEO Technologies
« Reply #37 on: 02/25/2009 01:04 pm »
He said physical size, not mass. CH4 is considerably denser than LH2, more than enough to offset its lower isp. The lander would end up heavier, and higher performance, but be the same size.

Ah, I see. In what way would that be an improvement though? I thought launch mass capacity was currently the limiting factor, not volume.
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Offline kraisee

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Re: DIRECT Applications Program - Mars & NEO Technologies
« Reply #38 on: 02/26/2009 10:45 am »
He said physical size, not mass. CH4 is considerably denser than LH2, more than enough to offset its lower isp. The lander would end up heavier, and higher performance, but be the same size.

Ah, I see. In what way would that be an improvement though? I thought launch mass capacity was currently the limiting factor, not volume.

HLLV's can enable this up to a decent level, but a Depot would be able to remove all of these constraints.

Your limiting factors then become the DRY mass of your spacecraft, the physical size of the spacecraft (wide diameter PLF's required for landers) and how many propellant delivery flights you (and your partners) can schedule & pay for.

Ross.
« Last Edit: 02/26/2009 12:08 pm by kraisee »
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Offline kraisee

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Re: DIRECT Applications Program - Mars & NEO Technologies
« Reply #39 on: 02/26/2009 10:57 am »
If 6 month missions are performed on the Moon and Mars the mass of the zero boil off hardware or the extra hydrogen or both has to be allowed for.  LOX/LH2 engines are not as good as they look.

Agreed.   The problem is that we just don't have sufficient experience with any others (except solids and RP1) to choose to confidently propose them as part of the critical path to success -- especially not in such a safety-critical role as the main descent engine of the lander!

RL-10's have been fired using a wide range of different fuels and oxidizers on the test stand, but none have ever been qualified for flight, let alone qualified for use with a human crew.   Make no mistake, that is still a long time and a lot of dollars away from being a reality -- even on such an engine which has already demonstrated the basic potential.

Because of that, anything which isn't LH2/RP1/solid is essentially relegated to being part of a future upgrade path and just can't be sensibly included as part of the initial-phase planning.

Ross.
« Last Edit: 02/26/2009 10:58 am by kraisee »
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