Re: An opportunity for VMS

In article <44CE391B.42389F10@xxxxxxxxxxxx>, JF Mezei <jfmezei.spamnot@xxxxxxxxxxxx> writes:
david20@xxxxxxxxxxxxxxxx wrote:
The ISS is expected to be 453.6 metric tons in weight, bigger than a 5 bedroom
house and measure 110 meters end-to-end.

The specifications of the habitat module for the Mars direct mission are
available at http://en.wikipedia.org/wiki/Mars_Habitat_Unit
Adding the figures up the total weight including crew is
45.49 Tonnes

ie about a tenth that of the ISS.


The space station is the currently at bare minimum to support 3 persons
for 6 months. In fact, it gets resupplies every 2 to 3 months.

If you really think that you can encase a crew for 6 months in a
telephone booth for a voyage to mars, you are crazy. And by the way,
where is the weight or engines, attitude control, solar panels, fuel
tanks, O2 and N2 tanks ? Water ?


I must apologise I misread the specification at wikipedia as the full habitat
module whereas closer reading shows it is only the specification of prototype
Mars Habitat units being tested on Earth by the Mars society.
So you are correct that it is probably missing components such as engines.
(other components such as Solar panels though are explicitly listed and I would
expect that water would be included in the "consumables for the crew" item).

However the missing components would not add enough mass to be anything like
the mass of the ISS.

(The use of consumables is listed on

http://www.geocities.com/marsterraforming/mannedmissions.html

)


The habitat unit is definitely big enough to support a crew for 6 months since
the Mars society has already tested this on earth.


Just because you can use a computer to create neat images of a concept
doesn't make that concept workable.


Mars direct is not my idea it has had scrutiny by a large number of experts.
There are a number of different variants including Nasa's Design Reference
Mission
(fuller detailsd of which are available from
http://exploration.jsc.nasa.gov/marsref/contents.html
)



And remember that you need to have enough supplies to return to earth.
One can argue that you'll send those supplies ahead of time and meet in
mars orbit. But even with that, the main ship will require barebones
supplies to keep the crew alive to earth should that rendez-vous fail in mars.


Water, Oxygen and fuel (both for exploration etc on Mars and for the return
journey) will be manufactured on Mars.
Food supplies will obviously need to be transported - but see
http://exploration.jsc.nasa.gov/marsref/contents.html
consumables list for the requirements for a 600 day stay on the surface.



Furthermore, right now, when something breaks on the ISS, generally the
russians can send a replacement part within roughly 2 months. But some
of the bigger parts require the shuttle (such as the failed control
moment gyros) and those took years to ship up. On a mission to mars,
they won,t have that luxury. They either need full inventory of spare
parts, or ability to repair faulty ones. And this experience is being
gained on the ISS right now (especially on the russian side who are less
affraid to thinker with stuff, while on the USA side, they prefer to
just shut the unit down and not let the crews thinker with it).


Which is why you send unmanned vehicles to Mars before hand.


Right now, when station crews return to earth, they need to have only
enough strength to push a few buttons and make a phone call on an
irridium phone to provide their lat/long, and then wait for the recovery
crews to get there and pull them out of the soyuz and lay them up on
lounge chairs. When they land on mars, they will be required to be
more or less fully functional. And that means a far more rigorous
exercise regime while on transit to mars, and thus more exercise
equipment. (and also less time to do any work to maintain the ship).


The ISS crew are in weightless conditions. Mars direct tethers the habitat
module to the booster rocket used for launch and spins the assembly providing
Mars level gravity.


While one would not expect the whole ship to land on mars and the
artists' concept of the "mars direct" ship may seem to be workable for
the mars landing, it isn't for the whole trip to/from mars.

The NASA variant has some changes from the original Mars cdirect but is based on
the same fundamental ideas - hence it appears experts including Nasa disagree
with your assessment.


David Webb
Security team leader
CCSS
Middlesex University

.

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