The first human mars mission?

Tom Merkle wrote:

Dick Morris wrote in message ...
John Schilling wrote:

Dick Morris writes:


The biggest question is whether it will work with Mars dust in the air
it's pulling in. That's a little more difficult to simulate, since we
don't *know* the exact composition and characteristics of the dust.

Zubrin addressed the dust issue in TCFM, as I recall. His approach was
to liquify the CO2 under pressure and then purify it by distillation, so
that any dust in the air would remain in the solution.

But there's still that pesky "liquify the CO2 under pressure" bit, which
requires refrigerators and compressors, with the moving parts and the
sliding seals, *before* you get rid of the dust. That machinery can
still get torn up if we underestimate the dust problem.

There is also the option of filtering the air before it gets to the
compressors. The engine in my car seems quite happy with that sort of
arrangement, since it's been running for almost 15 years with no obvious
signs of wear. Filtering can probably handle the vast majority of any
dust problem.
--
*John Schilling

Agree. Filtering technology is well understood. HEPA filters in most
earthbound vacuums are capable of removing dust greater than .01
microns in size. I don't think this is a serious barrier. The real
question is how much it will cost to develop a storage and fueling
method,

The propellants will be stored in the return vehicle propellant tanks as
they are made, so there will be no additional storage and fueling
requirements as such. There will just be some relatively small dia.
tubing to connect the propellant tanks with the chemical plant. The
tanks will have to be designed to store the liquid hydrogen during the
trans-Mars coast, so storing the LOX/methane propellants on Mars will
not be a great challenge. The development cost for the propellant plant
and plumbing will be a small part of the total development cost.

as well as a reliable LOX-methane engine capable of sitting
around for two years prior to launching.

This is an issue for every Mars proposal. If we can't design reliable
engines that can withstand the space (or Mars) environment for periods
measured in years then we won't go. The Russians know how to design
reliable rocket engines, and the RL-10 is also extremely reliable.
Rocket engines can be designed to be reliable if high reliabiity is a
requirement. They can also be designed for long-term storage, like the
engines on a Titan ICBM, though storage in space, or on Mars, is
admittedly a more difficult problem.

As usual with most gargantuan
engineering projects, the devil is not in the concepts but in the
details. How do you counter blow-back from a LOX-methane rocket big
enough to launch from the surface of mars to earth? It's not like you
can land a full launch pad and support facility.

The Apollo astronauts made it back from the Moon without a full launch
pad and support facility. ;-)

"Blow-back" is certainly an issue that needs to be investigated, but it
will probably turn out to be no more of a problem on Mars than it was on
the Moon. The LM Descent Engine generated about as much thrust during
the final braking maneuver as the Ascent Engine did during liftoff, and
there was very little evidence of cratering even directly under the
engine. The exhaust simply spread out horizontally in all directions.
A vehicle returning to Earth from Mars will have a much greater thrust
level, but the total exit area of the propulsion system will also be
much greater, so the pressure of the exhaust on the surface may be about
the same. Like the LM, the ERV propulsion system will be designed to
operate efficiently in a vacuum, or very low pressure (~1% Earth
sea-level) environment, so the exit pressure will be quite low.

And the reduced
gravity's gonna have even more fun with all the machinery required,
especially if you need to include a reactor to provide the required
electrical power.

All of the required machinery could be designed to operate even in 0-g
if necessary.

Typically rockets that require long-term on station time and
reliability have been hypergolic. Obviously this is not possible on an
ISRU rocket. Liquid rockets are notoriously finicky when it comes to
launch preparations. Can it all be managed from 30 light-seconds away?

The Apollo astronauts managed to fire four large liquid rocket engines
during each lunar landing flight. The J-2 engine on the SIV-B had
previously been fired during the orbital injection burn only a few hours
previously. The SPS engine was fired twice behind the Moon, approx.
half an hour after LOS, over a period of up to several days. RL-10
engines have been fired as many as seven times in a single mission.
Large liquid rocket engines can be fired without large ground support
crews fussing over them for days or weeks.

Can you get congressional support for a nuclear reactor on Mars?
That's the hard stuff, not trivial obstacles like dust in the martian
air or hydrogen storage problems.


Politics has always been the hard part. We still haven't got it right.

Tom Merkle

Henry Spencer wrote:

In article ,
McLean1382 wrote:
Even with LEO transit costs a couple of orders of magnitude less, you are still
going to have strong incentives to minimize mass. Getting from LEO to Mars and
back still requires a lot of delta v, even with aerobraking.

So? Fuel is cheap, especially if you don't insist on using liquid
hydrogen. Looked at carefully, almost always the way you minimize cost is
to throw mass at problems, rather than throwing engineering man-years at
them.

For example, it is almost certainly cheaper to use LOX/methane than to
solve the problems of long-term LH2 storage in space. (Slightly modified
RL10s have been run on LOX/methane.)

Could you define "slightly"? A reference detailing the changes would be
appreciated.

So what if it makes the vehicle
heavier? Almost all of the mass is either methane, which is cheap, or
LOX, which is almost free. If the cost of getting them into LEO is
reasonable, using them is better than inventing new LH2 technology.

And the need for
extreme reliability will drive up development costs in any case.

Not if you send along tools and spare parts (and guys who know how to use
them) instead, and provide enough redundancy and backups to give time for
them to be used. In highly-lethal Earth environments, like Antarctica, we
don't see anywhere near the same development costs. If you're going to
the trouble of sending people as part of the mission, you should exploit
their capabilities to the fullest to make the engineering easier.

Yes, this implies a somewhat larger expedition -- multiple ships,
substantial crews. That is actually cheaper than a cut-to-the-bone
minimal expedition where everything *has* to work perfectly because
there's no safety margin and no repair option.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

(Henry Spencer) wrote:

In article ,
McLean1382 wrote:

And the need for
extreme reliability will drive up development costs in any case.

Not if you send along tools and spare parts (and guys who know how to use
them) instead, and provide enough redundancy and backups to give time for
them to be used.

The problem here is that it takes a little time to make sure your
pre-calculated MTBF and MTTR are in the ballpark, and that your spares
store has the proper width and depth. There's the issue of your tool
locker and ensuring that cal requirements can be met. There's the
issue of ensuring that the sell-by dates on spares and tools will
cover the life of the mission. There's the issue of ensuring adequate
training and documentation to support preventative and corrective
maintenance. There's the *big* issue of ensuring that the equipment
is designed to be serviced and maintained. There the issue of setting
up maintenance schedules and procedures...

No show stoppers, but a lot of engineering man-hours, a lot of
seemingly trivial details, and a fair amount of money. The Navy has
been wrestling with these problems for decades now, and is just now
getting the general philosophy down, yet each new class of ship has to
climb up a pretty steep learning curve getting all the details right.

In highly-lethal Earth environments, like Antarctica, we
don't see anywhere near the same development costs.

Partially because Antarctica isn't nearly as lethal as Mars, by a long
shot. Partially because a great deal of Antarctic equipment is either
COTS or near enough to it as the same environment is found in parts of
Alaska as well as in the Scandinavian countries and Artic expeditions.

If you're going to the trouble of sending people as part of the mission, you
should exploit their capabilities to the fullest to make the engineering easier.

You don't make the engineering easier by incorporating repair options
and spares, you just move the engineering problems into different
areas. The military and companies like the telco frequently choose
locally repairable equipment over depot level maintenance not to
reduce costs, but to increase availability at some cost in reliability
(mostly due to errors in maintenance).

Yes, this implies a somewhat larger expedition -- multiple ships,
substantial crews. That is actually cheaper than a cut-to-the-bone
minimal expedition where everything *has* to work perfectly because
there's no safety margin and no repair option.

No, Larger expeditions like this transform development costs into
operational costs. They explicitly don't reduce the costs of launch.

D.
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(Christopher) writes:

On Thu, 2 Oct 2003 20:41:12 GMT, Dick Morris
wrote:


(Above all, we should never, never, EVER design a mission based on
technology advances that are ASSUMED will be available by the time
development is complete. If the technology advances do not materialize
on time, then virtually the entire development team will be sitting
around playing computer solitair or surfing the net while technology
catches up, or the program will require a very expensive redesign.
NEVER use an operational program as a device to "push the technology".
NASA has shot itself in the head doing exactly that for the last 30
years: Shuttle, ISS, NASP, SEI, X-33, SLI.)

Going by that assumption then the VASIMR rocket won't be used for a
human Mars shot, as several concepts propose using it for a fast trip
to Mars i.e. using a plasma rocket to lessen the effects of micro g on
the crew, and cosmic and solar radiation that a more longer journey
time would have.


It is almost certainly correct that the VASIMR rocket won't be used for
a human Mars shot, and the fact that it is advertised as The One True
Technology We Need to Develop to Do Human Mars Shots Right is, as Mr.
Morris notes, precisely why not.

This is not to say that we won't use a "plasma rocket". We'll just
use a plasma rocket that isn't named VASIMR, or maybe an ion drive
that also isn't named VASIMR. Say, a descendant of one of the various
systems along those lines that has been quietly developed over the past
few decades, have over the past few years become standard on commercial
spacecraft, have gone interplanetary on technology testbed spacecraft,
and have *not* been tied to the holy grail of the Manned Mars Mission.

You want your new technologies to cut their teeth in application where
the only thing required is that they work, where no great tragedy will
befall if they fail, and where as a consequence there will never be a
flock of reporters extolling The Technology That Will Take Us to Mars.
Because a manned Mars mission, if that is your goal, requires that
*all* the new technologies work at cost of enormous tragedy if any
fail.


--
*John Schilling * "Anything worth doing, *
*Member:AIAA,NRA,ACLU,SAS,LP * is worth doing for money" *
*Chief Scientist & General Partner * -13th Rule of Acquisition *
*White Elephant Research, LLC * "There is no substitute *
* for success" *
*661-951-9107 or 661-275-6795 * -58th Rule of Acquisition *

John Penta writes:

On 1 Oct 2003 14:44:00 -0700, (John Schilling)
wrote:

John Penta writes:

Why do I say that?

1. This...fixation with the private sector: Folks, there is NO PROFIT
IN A MARS FLIGHT.

???

James Cameron could bring in a gigabuck in gross revenues from the first
manned Mars mission with one lobe tied behind his brain.

Making a *net* profit is tricky. It's going to depend on both cost
reduction and cost sharing, and it's not going to happen tomorrow.

But making "NO PROFIT!" a capitalized absolute, is silly.

I was trying to rattle cages; I see I have done so. (Oh, I wouldn't
DOUBT we could get plenty of gross revenue. Would it, however, break
even? Not likely.)


You do understand that about every other month someone shows up here
to "rattle our cage" with the profound observation that there is NO
PROFIT! to be had in space exploration, etc?

First person to do so can plausibly claim to have been trying to
introduce a new idea into the discussion. After that, it's the mark
of an asshole or an ignoramus.


My personal opinion is that, at the present time, a Mars mission would
be skipping a step, namely a moonbase. And I mean a FULL moonbase,
where we can get used to living for really, really long times off of
the Earth and where we can learn the kind of construction techniques
that would be required for a Mars mission.

See, this is why NASA wanted four hundred billion dollars to go to Mars.
Well, one of the reasons.

And it simply does not hold up to examination. There is nothing of any
great importance that could be learned on the Moon that cannot be learned
just as well in LEO and/or on Earth. In particular, the Moon is not Mars,
and its environment in most relevant parameters is as far from that of
Mars as Mars is from Earth. The Moon is *not* the stepping-stone to
Mars, it is just a different place we can go.

You can actually make a pretty good argument that a permanent, substantial
Moon base would be a *better* mid-term goal than manned Mars exploration.
But not that the one is a prerequisite to the other.


--
*John Schilling * "Anything worth doing, *
*Member:AIAA,NRA,ACLU,SAS,LP * is worth doing for money" *
*Chief Scientist & General Partner * -13th Rule of Acquisition *
*White Elephant Research, LLC * "There is no substitute *
* for success" *
*661-951-9107 or 661-275-6795 * -58th Rule of Acquisition *

In article ,
Dick Morris wrote:
For example, it is almost certainly cheaper to use LOX/methane than to
solve the problems of long-term LH2 storage in space. (Slightly modified
RL10s have been run on LOX/methane.)

Could you define "slightly"? A reference detailing the changes would be
appreciated.

The RL10 paper in "History of liquid rocket engine development in the US
1955-1980", AAS History series #13, 1992, alludes to pump and turbine
modifications, plus passage restrictions to increase coolant velocity,
according to my notes. I don't recall it going into much detail, though.

There's also mention of it in the RL10 paper in NASA CP-3112, "Space
Transportation Propulsion Technology Symposium", 1970, and in NASA
CR-54445 and CR-72147 on unorthodox hydrocarbon fuels.

If there's ever been a survey paper going into detail about all the wild
and wonderful things P&W has tried with the RL10, I'm not aware of it.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

On Mon, 6 Oct 2003 18:56:24 GMT, (Henry Spencer)
wrote:

In article ,
Christopher wrote:
There's lots of unexplored potential left in chemical rockets, actually.
Very little serious R&D has been done on them in the last forty years,
other than (basically) incremental refinements of early-1960s designs.

The SSME uses hydrogen and oxygen, and that's a pretty good
combination for fuel.

Actually it's not a terribly good combination, except for some specialized
purposes. Hydrogen is a lousy fuel; people are mesmerized by its high
Isp, and forget the heavy tanks and plumbing and the poor engine T/W.
What we care about is delta-V, not Isp, and the former is often actually
easier to get with fuels like kerosene.

Could the shuttle go up just as well using paraffin/kero and lox the
same as with it's current hydrogen fuel?

Even setting that aside, note that the SSME is an incremental refinement
of Pratt&Whitney's 1960s RL20/XLR129 high-pressure-engine work. Nothing
very new there.

Didn't know that.

The improvements to be had are (with possible minor exceptions) not in new
fuels, but in better engines -- higher expansion ratios with altitude
compensation, lighter weight, longer operating life, lower costs.

So, what your saying is rocket engines could be developed like the
internal combustion engine has been, in that the car engine of 1963 is
a totally primative engine compaired to the 2003 car engine as we have
seen 40 years of development take place?


Christopher
+++++++++++++++++++++++++
"Kites rise highest against
the wind - not with it."
Winston Churchill

Henry Spencer writes:

So? Fuel is cheap, especially if you don't insist on using liquid
hydrogen.

Right, but twice as much fuel requires twice as much engine to push it, and
engines *aren't* cheap.

Will McLean

In article ,
Christopher wrote:
...Hydrogen is a lousy fuel; people are mesmerized by its high
Isp, and forget the heavy tanks and plumbing and the poor engine T/W.
What we care about is delta-V, not Isp, and the former is often actually
easier to get with fuels like kerosene.

Could the shuttle go up just as well using paraffin/kero and lox the
same as with it's current hydrogen fuel?

The SRBs might have to get somewhat larger, because the gross liftoff mass
of the orbiter plus ET would be higher. On the other hand, the ET itself
would get smaller and lighter (heavier when filled, but lighter when
empty) -- it's currently mostly LH2 tank.

Even setting that aside, note that the SSME is an incremental refinement
of Pratt&Whitney's 1960s RL20/XLR129 high-pressure-engine work. Nothing
very new there.

Didn't know that.

P&W was intensely ****ed off about it too -- from their viewpoint, NASA
led them on and had them do all the pioneering development of a somewhat
difficult technology, and then when it came time for a big production
contract, handed it to their arch-competitor and told them to get lost.

The improvements to be had are (with possible minor exceptions) not in new
fuels, but in better engines -- higher expansion ratios with altitude
compensation, lighter weight, longer operating life, lower costs.

So, what your saying is rocket engines could be developed like the
internal combustion engine has been, in that the car engine of 1963 is
a totally primative engine compaired to the 2003 car engine as we have
seen 40 years of development take place?

Right general idea, except that I would compare today's rocket engines to
the car engines of 1903, or maybe 1893, not 1963.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

In article ,
McLean1382 wrote:
So? Fuel is cheap, especially if you don't insist on using liquid
hydrogen.

Right, but twice as much fuel requires twice as much engine to push it...

Not in space it doesn't, not necessarily. Quite modest accelerations
often suffice. (For example, Cassini's Saturn Orbit Insertion burn lasts
an hour and a half for a total delta-V slightly above 600m/s.)

...and engines *aren't* cheap.

Off-the-shelf engines are not that expensive, unless you insist on using
SSMEs. As of about 15 years ago, RL10s cost $2M each, and P&W thought
that price could be roughly cut in half if you bought several dozen at a
time with minimum paperwork.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |