NASA adopts the best of Zubrin's ideas, eventually

[mmeijeri]

Earth Departure: LOX/LH2 and/or LOX/Kerosene.

I'd say LOX/LH2 for transport of individual modules from LEO to L1/L2 and hypergolics from L1/L2 to TMI. Both segments are part of Earth departure.

Mars Arrival: Option 1 - Aerocapture then powered & parachute/powered descent. Propellant? Storables, because of the long voyage through interplanetary space: devoting mass and technology to zero-boiloff will reduce Hab/Lander down mass. Option 2 - Direct descent with no aerocapture; parachute & powered descent. Propellant; again storables. Technology Risk: Low.

I'd say propulsive insertion into high Mars orbit, possibly a Mars Lagrange point. Much lower technology risk, but also more propellant-intensive. Of course, I like propellant-intensive solutions. The reason for braking into high rather than low Mars orbit is that it requires much less propellant. We also need to avoid outgrowing a transfer stage that will still fit inside an EELV fairing.

Mars Ascent to Orbit: Option 1 - Storables all the way, but mission down mass reduced. However, low technology risk. Option 2 - ISRU for LOX: solar & RTG-powered ISRU plant. Fuel? Kerosene or Ethanol. Technology Risk: Moderate.

I doubt avoiding ISRU (and surface nuclear power) is practical, and using LOX/hydrocarbon should be easier than hypergolics.

Earth Return Vehicle from Martian orbit: Storables. Technology Risk: Low. This vehicle would be waiting in Martian orbit to do its job for at least two years, so proven hypergolic technology it should be.

Agreed.

*Bonus Category: Launchers - OPTION 1: Mixed fleet of Delta IV-Heavy (uprated to 40+plus tons = known, simple upgrade options), Atlas V, Falcon Heavy and Ariane V. OPTION 2: SLS & Falcon Heavy. Earth Re-entry spacecraft? Either Orion or Dragon, I have no preference.

The main reason I see for an EELV Phase 1 is ACES the EDS, with the bigger launcher as an inconsequential side-effect. No need to avoid use of commercially available large launchers, but no real need for such use, and not much benefit either.

[mmeijeri]

Mars Odyssey, MRO, and MSL have radiation sensors.

Important data, but it doesn't assess the effect of various designs of radiation shielding or the biological end effects of the internal radiation environment. Tissue cultures could help with that.

[Jim]

Mars Odyssey, MRO, and MSL have radiation sensors.

Important data, but it doesn't assess the effect of various designs of radiation shielding or the biological end effects of the internal radiation environment. Tissue cultures could help with that.

how do you know about the shielding aspects?

[mmeijeri]

how do you know about the shielding aspects?

I meant testing various designs of shielding for manned spacecraft to reduce the biological end effects. Were you suggesting there are (physical) radiation shielding experiments aboard the probes you mentioned, rather than just measurements of the local radiation environment?

[mmeijeri]

And as for L-2 Gateway Station? I'd say it was almost essential.

An MTV parked at L1/L2 would essentially be a gateway station.

[QuantumG]

What's cool about it? I'm surprised I have to point it out to you: the ability to - theoretically - take a crew to Mars in about 40 days.

It's not free - that's Zubrin's point. Even if you could take a crew to Mars in about 40 days, you have to pay for it with decreased crew safety. If your reason for wanting to go faster is better crew safety then you've just negated your goal.

(I've explained it three times now).

[go4mars]

Is Zubrin dismissing tether architectures?

No.  Zubrin is a proponent of tether architectures so that people arrive strong. 

He's built some pretty compelling ISRU demonstrators. 

Back to the original post, my belief is that his most pregnant ideas yet to be adopted in the main stream as obviously good ideas are "transorbital railroad" and "nuclear salt water".

[douglas100]

Zubrin has some interesting ideas and is very good at thinking outside the box. But...

Nuclear salt water has never been done. It would have to be developed and tested. Controlling the fission reaction in such a dynamic system would be far from simple. The exhaust products would be so radioactive as to make testing on Earth very difficult and expensive. And politically it's difficult to imagine this being acceptable. Even getting the propellant into space where the system would have to be be used, would be hazardous: imagine what would happen during a launch accident where the payload is many tons of uranium salt solution. I don't see being developed.

The transorbital railroad proposal is essentially a government launch subsidy. I've no idea what the political feasibility of such a scheme would be. Whether it would stimulate the launch market remains to be seen. What effect it might have on international trade agreements is another open question.

I think you're right in saying that Zubrin's ISRU ideas are his best. Some are almost mainstream already.

[pathfinder_01]

Ah the lone voice in the wilderness here. 

Electric propulsion is fine, even solar electric is fine for cargo or delivering propellant to mars.

It just gets iffy when you want it to move the crew to Mars with it as main propulsion. Then you may need nuclear power.

You could also use it to move a chemically powered Mars spacecraft assembled in LEO out to L1/l2(or a high earth orbit) reducing the mass of chemical propellant needed to get to mars and perhaps the overall mass of the mission.  That ability could reduce the launch costs of such a spacecraft.

[A_M_Swallow]

And as for L-2 Gateway Station? I'd say it was almost essential.

An MTV parked at L1/L2 would essentially be a gateway station.

True but we would still want to make trips to the Moon whilst the MTV was at Mars.

I suspect that the initial EML Gateway Station can be smaller than the ISS.

[MATTBLAK]

What's cool about it? I'm surprised I have to point it out to you: the ability to - theoretically - take a crew to Mars in about 40 days.

It's not free - that's Zubrin's point. Even if you could take a crew to Mars in about 40 days, you have to pay for it with decreased crew safety. If your reason for wanting to go faster is better crew safety then you've just negated your goal.

(I've explained it three times now).

With this post, you've selectively ignored what I wrote immediately afterwards! This is not the Monty Python argument sketch you know!!

[mmeijeri]

True but we would still want to make trips to the Moon whilst the MTV was at Mars.

You could keep a spare at L1/L2. Call that a gateway station if you will, but my point was that you don't need to design a separate station or even build a spare if you can't afford it. Similarly, a lander could be its own makeshift gateway station.

[go4mars]

I know Bob prefers nuclear power on the surface of Mars, and chemical for  propulsion...   Are there major show-stoppers for designing a fission power generator that would be pretty good for both?

[go4mars]

Asking me?  No I don't mean a Mars transfer vehicle / cycler.  I mean a reactor you would use for inter-space propulsion on the way there, and also on the surface of Mars.  Same unit.  It's use on the way there would probably need to be merely an auxillary to the chemical prolusion.

It's been a number of years since I've read "The Case for Mars".  But I know he didn't want to waste time developing an in-space advanced propulsion system.  But he wanted nuclear for the surface.  Presumably, he considered the power to weight ratio as not worthwhile or maybe had safety reservations. 

Now that I'm thinking about it: using his Mars Direct architecture, if it arrives on the preceding conjunction with the earth return vehicle anyways, and the manned lander is the heavier chunk, then I guess it becomes more easy to see that the incorporating it to help on the journey doesn't make a lot of sense.  Added comlexity and risk. 

Edit add: just noticed to context I hadn't paid attention to up the thread.
Was assuming power use could be made to be similar.  Will need to consider further.  And revisit that book of his.

[savuporo]

MGB should have been flown and supported much better, and something along its lines should be done for radiation as well, outside the van Allen belts of course. Maybe now that we actually have a working microfinancing platform, it should be tried again.
All these discussions around mars architectures would be far less theoretical if such basic ( and incredibly cheap ) data acquisition missions were flown.

[MATTBLAK]

True but we would still want to make trips to the Moon whilst the MTV was at Mars.

You could keep a spare at L1/L2. Call that a gateway station if you will, but my point was that you don't need to design a separate station or even build a spare if you can't afford it. Similarly, a lander could be its own makeshift gateway station.

Re-usable MTV? With storables, it takes the crew to Mars for either propulsive braking into High Mars orbit (DEIMOS!!) or aerocapture. Then it waits for the crew to return and head back to Earth for propulsive braking into L-2. To do all that would take a heck of a lot of propellant, but at least between TMI windows there would be lots of time to fill it back up with a 'Propellant Railroad' from Earth. Maybe its propulsion/propellant module could be detachable; dock a new one to it between each Mars mission or when its design life is expired, whichever comes first. Engines? I suggest a quartet of AJ-110 derived motors.

How big would an empty tank/engine module for a mission like this be if you had to launch it on an existing EELV? Or would it have to be launched in two separate engine & tank packages?

[MATTBLAK]

Asking me?  No I don't mean a Mars transfer vehicle / cycler.
Edit add: just noticed to context I hadn't paid attention to up the thread.
Was assuming power requirements would be similar.  Will need to consider further.  And revisit that book of his.

Sorry: was replying to mmeijeri! Have changed previous post to clarify that.

[Kaputnik]

And ISRU? Damned nice to have - maybe even a mission success deal-breaker. But NOT essential in terms of actually going there. Though without ISRU, shortcuts in crew size and mission duration/capability would have to be made, reducing the value of even doing it in the first place. And as for L-2 Gateway Station? I'd say it was almost essential.

I would put those the other way around.
Show me how you put together a non-ISRU Mars Ascent Vehicle without needing some Sea-Dragon sized LV to get it there.

My 'wish list' for technology developments the enable a Mars mission goes:
ISRU
Large scale EDLS
Surface power, EVA ops, and hab systems
In-space hab systems

Those are the real breakthrough developments that we need. Everything else, from aerocapture to L2 stations to super-LVs, are just 'nice to haves'.

[MATTBLAK]

"Show me how you put together a non-ISRU Mars Ascent Vehicle without needing some Sea-Dragon sized LV to get it there."

Well, you are overstating things a tad:a non-ISRU Ascent Vehicle need not be a 'Battlestar Galactica' sent there on a rocket twice as powerful as Ares V!! First of all, I only said that a non-ISRU Ascent Vehicle was an option, and not the preferred one at that.

Following figures approximate; since Mars mission mass numbers are still debated - The dry mass of the Mars Ascent Vehicle (MAV)  according to the NASA Mars DRM-3 study - is 20 tons, give or take consisting of both the Descent and Ascent portions, plus 20 tons of cargo sent as down mass:

http://ares.jsc.nasa.gov/HumanExplore/Exploration/EXLibrary/docs/MarsRef/addendum/index.htm

This down mass includes the ISRU 'feedstock', a Rover, scientific equipment, tools, spares, the nuclear reactor for ISRU etcetera. If this vehicle is landed with 6 tons of LH2 feedstock for ISRU creation of LOX/Methane, this is leveraged to produce more than 30 tons of propellants to launch the ascent vehicle to a Mars Transfer Vehicle or a dedicated Earth Return Vehicle in Martian orbit. We're assuming that the MAV would use this approx 30 tons of propellant to liftoff only the crew cabin, the Ascent stage motor, the crew and their Martian regolith & rocks, all massing about 15 tonnes at Martian liftoff - leaving the legs, descent motors and cargo pallet behind.

Since hypergolic propellants are between 10 and 15% percent less efficient than LOX/CH4, if we halved the vehicle's cargo downmass load - including deleting the nuclear reactor - we could more than make up for the loss in efficiency.

But if the Ascent Vehicle is made as basic and bare-bones as possible: a small cabin derived from Dragon or another, all-composite capsule, bolted to an Ascent engine, RCS sets and fuel tanks. Think of it as a "Apollo Lunar Module Ascent Stage on Steroids".

Apart from the hypergolic propellant load, all this craft would be lifting to Martian orbit would be a crew (2 or 3?) and their load of Martian rocks and regolith and maybe some data storage blocks. So it doesn't have to be as big or complex as the 44 ton (landed), 15 ton (ascending) NASA DRM-3 design for 6 crew.

Or if you wanted to meet ISRU halfway and only produce LOX oxidizer to supplement some landed kerosene or ethanol - this could use a 5 metric ton combined solar and RTG package to slowly produce the LOX only. And you could trade some of that 5 tonne increase in mass for cargo down mass; as you'd be using more powerful LOX/Kerosene/Ethanol for descent propulsion, not less efficient storables, to compensate for the mass of the ISRU package in the first place.

But let me state for the record: I am in favour of ISRU for Mars.

But an all-hypergolic Ascent Vehicle doesn't have to weigh 60 or 70 tonnes at Trans-Mars Injection. Launched on an uprated EELV or Falcon Heavy, the Hypergolic 'basic' MAV with Empty propellant tanks would mass about 16 metric tons, Descent/Ascent stages all up with little or no cargo. I say make a separate, dedicated Cargo Lander by deleting the weight of the 4 ton composite crew cabin. Before Earth Departure, load it with fuel from a Prop. Depot or Propellant Delivery Modules until it contains enough hypergolics to descend to the Martian Surface. For a bare-bones 2 or 3 person Ascent vehicle weighing half that of the 6 person DRM-3 design, total hypergolic propellant loading would be about 35 tons - 15 tons for a descent assisted by frictional slowing and parachutes, plus 20 tons to later get the craft into orbit to meet the ERV or MTV.

As I said, by making the MAV basic with no 'bells & whistles' and keeping bulk cargo for another lander, you don't need a 'Sea Dragon' to send it to Mars!! A couple Phase 1 EELVs, Falcon Heavies or one SLS Block 1B could do it. But yes, if you wanted a 6x person version with lots of cargo down mass, expect a much heavier vehicle. If you wanted to lift a hypergolically propelled big, 6 person MAV then yes, get a bigger rocket than even Ares V would have been.

[A_M_Swallow]

{snip}
But if the Ascent Vehicle is made as basic and bare-bones as possible: a small cabin derived from Dragon or another, all-composite capsule, bolted to an Ascent engine, RCS sets and fuel tanks. Think of it as a "Apollo Lunar Module Ascent Stage on Steroids".

The SEV weights about 3 tonnes and supports 2 men.  It can be used as the lander's cabin, to move around on Mars and the Ascent stage's cabin.
http://www.nasa.gov/pdf/464826main_SEV_FactSheet_508.pdf

If your stores are landed separately the Space Exploration Vehicle (SEV) is the idea vehicle to go and get them.  Possible using the MMSEV version.

Apart from the hypergolic propellant load, all this craft would be lifting to Martian orbit would be a crew (2 or 3?) and their load of Martian rocks and regolith and maybe some data storage blocks. So it doesn't have to be as big or complex as the 44 ton (landed), 15 ton (ascending) NASA DRM-3 design for 6 crew.

Or if you wanted to meet ISRU halfway and only produce LOX oxidizer to supplement some landed kerosene or ethanol - this could use a 5 metric ton combined solar and RTG package to slowly produce the LOX only. And you could trade some of that 5 tonne increase in mass for cargo down mass; as you'd be using more powerful LOX/Kerosene/Ethanol for descent propulsion, not less efficient storables, to compensate for the mass of the ISRU package in the first place.
{snip}

The waste product from electrolysing CO₂ is carbon monoxide, a medium power fuel in its own right.  Lowish Isp means that bigger but empty pair of fuel tanks are needed.