Problems with getting to Mars

1. Flight time - this can be overcome with an increase in escape thrust -
either a large chemical rocket or nuclear/electric as suggested by Tom
Stafford at the President's Commission on Moon, Mars and Beyond conference
(February 11, 2004 - Washington, DC). Nuke/electric has to be developed but
there are even alternatives (using existing systems in new ways rather than
new systems).

2. Communications - Apollo had a ~3 second round-trip for comms. Mars
has nine minutes - 180 times longer. Mars is also going to be on the
opposite side of the Sun for a long time - how do you communicate
through/around the Sun?

3. Systems reliability - because of point 1 and 2 and also for this
reason: With Apollo 13, the crew would only have had to remain in their
pressure suits for 4-5 days - going to Mars, the crew would have to remain
in their suits for 100 or more days if there was no pressurised environment.
Pressure hull integrity will be of paramount importance. Yes, there are
systems that can be used to seal a leak (ISS has something as I recall), but
what if the pressure leak isn't detected (ISS pressure is monitored from the
ground).

Feedback please.

--
Alan Erskine
We can get people to the Moon in five years,
not the fifteen GWB proposes.
Give NASA a real challenge

"Alan Erskine" wrote in
:

1. Flight time - this can be overcome with an increase in escape
thrust - either a large chemical rocket or nuclear/electric as
suggested by Tom Stafford at the President's Commission on Moon, Mars
and Beyond conference (February 11, 2004 - Washington, DC).
Nuke/electric has to be developed but there are even alternatives
(using existing systems in new ways rather than new systems).
Halving the time, needs something like 10 times the delta-v. Not much you
can do here. Of course if you can shrink the transit time by even a month,
it does make the short-stop Mars misison profiles much more attractive.
Using pure Hohmann transfer orbits, your visit to Mars willbe either 1
month, oor about 14 months in duration. Cutting 1 month off transit time
will increase the short-stop stay to 3 months, making it a practical
option.

2. Communications - Apollo had a ~3 second round-trip for comms.
Mars has nine minutes - 180 times longer. Mars is also going to be on
the opposite side of the Sun for a long time - how do you communicate
through/around the Sun?
Comms delay: Live with it. Use message queues rather than query-response-
nextQuery approach. Run the routine actions of the mission *from the ship*
not from the ground. Apollo-style ground micromanagement is totally
impractical at Mars distances.
Solar obstruction: A Relay craft virtually anywhere other than in earth or
mars orbit. Obviously, the mission craft will have a stronger transmitter
than current power-limited mars missions. Any craft capable of carrying
astronauts will have several magnitudes more electrical power at its
disposal than the current Mars satellites.

3. Systems reliability - because of point 1 and 2 and also for this
reason: With Apollo 13, the crew would only have had to remain in
their pressure suits for 4-5 days - going to Mars, the crew would have
to remain in their suits for 100 or more days if there was no
pressurised environment. Pressure hull integrity will be of paramount
importance. Yes, there are systems that can be used to seal a leak
(ISS has something as I recall), but what if the pressure leak isn't
detected (ISS pressure is monitored from the ground).

Leak detection:
Airtight Honeycomb doublehull. Each cell filled with inert gas, at lower
than interior pressure. Seperate pressure sensor inside each cell. A leak
in outer hull will cause cell pressure loss. A leak in inner hull will
trigger cell overpressure. Make cells small enough to localise the leak,
large enough to keep mass overhead of cell dividers & sensor network down.
Capability to seal a localised puncture by flooding a cell with a sealant.
(something similar to polyurethane foam comes to mind)

Other critical system will require a similar approach to failure
management. Excess safety margin if you can afford it, redundancy where
nothing else works, fault tolerance where you can. Minimisation of the
effort needed to localise and correct a problem.

This is the sort of knowledge I *THOUGHT* the ISS was supposed to be for.
The recent difficulty in locating the leak was very, Very dissapointing.

Some suggestions to improve relyability of long-duration spacecraft:
-Keep the count of holes in the pressure hull to a minimum. Rather spend
big bucks on multiple superb cameras+viewscreen set than punch a hole in
your hull to mount a window! Crew in a vessel do *not* need to see outside,
our experience with long-duration subs proves this.

-Dont rely on humans in your routine safety watchdog roles. Thats what
simple sensors and computer checking are for! Humans are not good at
routine-but-critical jobs. They get bored. Computers dont.

-Spend some time on thinking about the ergonomics of your crew's actions.
Again, the recent window-leak on ISS comes to mind. If you put a window
where the crew can get to it, but you fail to provide an easy and solid way
for them to support themselves there, they *will* grasp onto inappropriate
spots. Again, this should be a major focus of research on ISS, rather than
the low-priority thing it is currently considered as.

-Use passive methods wherever possible, rather than active methods. For
example, dont cool your mission-critical circuitry with a fan, instead use
passive heat conduction for cooling.
An air-blowing fan is prone to:
+Make noise & vibration.
+fail if its power fails or even degrades as to voltage.
+fail if ambient air is lost, by puncture or whatever.
+migrates dust into sensitive systems.
+is subject to mechanical wear.
+chokes to death if some floating debris, especially liquids, hit it. This
demands very good filters. Which demands the filters be replaceable on a
long mission. Which demands storage of spare filters. which.... etc !!!
The extra mass for a passive cooling system is likely less than the extra
mass of the active cooling + all its support systems.
Note that I use this as an example only, obviously *all* systems should be
considered in a similar light. And yes, again this is the sort of research
I expected the ISS to be used for, but it seems to not be the case.

On Tue, 30 Mar 2004 18:44:19 GMT, "Alan Erskine"
wrote:

2. Communications - Apollo had a ~3 second round-trip for comms. Mars
has nine minutes - 180 times longer. Mars is also going to be on the
opposite side of the Sun for a long time - how do you communicate
through/around the Sun?

It is actually quite rare that Mars passes directly behind the Sun
from Earth's vantage point, due to angles to the ecliptic at which
both Earth and Mars orbit the Sun. It usually passes a little above or
below the Sun as seen from Earth. Even that causes interference
problems, however, so you'd launch a relay satellite somewhere in
orbit around the Sun either ahead of or behind Earth or Mars.

Brian

Flight time:

Flight time means longer exposure to deadly radiation.
Multiply by two for the return trip.
22 months exposed to space is quite a feat... specially
if you want to go on living afterwards.

But that is not so much of a problem. Much worse are
the conditions when you arrive at Mars:

Hexavalent Chromium is the most cancerigenic
substance known. It is probably present in the
surface of mars.

Very fine hard dust particles provoke asbestosis
(miner's sickness) and cancer.

Water is scarce and, when present, well mixed with
sulfuric acid.

The dust will ruin the electronics, choke the filters, and be
a constant hazard. It is very difficult to keep outside unless
you have a lot of equipment and abundant energy.

Energy is scarce. Solar panels are the only solution since
carrying a nuclear reactor to Mars is a bit heavy for
today's rockets, not to speak about the increased
radiation dose of a crew that lives for 22 months
at a few meters from a nuclear reactor!

That means that huge solar arrays must be established
and kept dust free to ensure the survival of the humans.

No oxygen, no food, everything must be carried
from earth.

And do not forget reliability. Any equipment
failure means death. All system must function
without a flaw for 30 months. We have never
done that, and this will be the most difficult part.

Human space exploration is impossible with today's
technology.

More rational is to do what we can do instead of
dreaming sci-fi stories.

The only solution is to improve the current technology
and in the meantime promote automatic exploration!

Robots do not breathe, nor have any metabolism.
Supplies for all that disappear.

Robots can work on Mars without any cancer fears
and radiation hardened robots like Spirit or
Opportunity perform without flaws in Mars, at
knock-out radiation levels.

Robots do not need a return trip. We can leave
them there, once their useful life is finished. Half
of the supplies (and budget) are gone.

Robots can be sterilized, humans can't. If we
put only one human in Mars we will contaminate
the planet forever.

And I am convinced that life exists over there.

Robots are the best solution: The explorers drive
them surely, safely, without any risk for themselves
nor for the planet they are studying.

To make a vehicle able to cruise in space and
sustain itself for more than two years without
any help from earth is a technology beyond
our reach. We will arrive at that in the middle of
this century, but I would be surprised if it
was before.

Going to the moon is *much* easier. But many
do not realize the difference between a 7 day trip
and a 30 month trip...

We have to build the base technology yet. And
so long that base technology (creating artificial
ecological system self sustained for times more
than 30-40 months) is missing we will go nowhere.

Zubrin speaks of sending robots to put the supplies
over there, so that humans arrive at an easy to
build base.

But then?

Why go to that surface in person?

We will see many planets but surely we will
not go to the surface of each one: Take Venus
for instance. With a cozy 500 C a robot was
able to send a photograph before he died.

A human wouldn't even arrive at that...

Obviously Mars is much easier than Venus.
But still, at least 50-60 years away.

jacob navia wrote:

Water is scarce and, when present, well mixed with
sulfuric acid.

It's very unlikely there's sulfuric acid in any great
quantity on the surface of Mars, since it reacts rapidly
with olivine to form magnesium and/or iron sulfates.

Paul

Can a pulse dentonation jet be used with ions of oxygen?

Mike


Alan Erskine wrote:

1. Flight time - this can be overcome with an increase in escape thrust -
either a large chemical rocket or nuclear/electric as suggested by Tom
Stafford at the President's Commission on Moon, Mars and Beyond conference
(February 11, 2004 - Washington, DC). Nuke/electric has to be developed but
there are even alternatives (using existing systems in new ways rather than
new systems).

2. Communications - Apollo had a ~3 second round-trip for comms. Mars
has nine minutes - 180 times longer. Mars is also going to be on the
opposite side of the Sun for a long time - how do you communicate
through/around the Sun?

3. Systems reliability - because of point 1 and 2 and also for this
reason: With Apollo 13, the crew would only have had to remain in their
pressure suits for 4-5 days - going to Mars, the crew would have to remain
in their suits for 100 or more days if there was no pressurised environment.
Pressure hull integrity will be of paramount importance. Yes, there are
systems that can be used to seal a leak (ISS has something as I recall), but
what if the pressure leak isn't detected (ISS pressure is monitored from the
ground).

Feedback please.

--
Alan Erskine
We can get people to the Moon in five years,
not the fifteen GWB proposes.
Give NASA a real challenge

Another problem that may be extremely difficult to counter will be the
bordom that will occur during the coast period (to Mars and also on return).
How can the psychological problems that may result from this be countered?


--
Alan Erskine
We can get people to the Moon in five years,
not the fifteen GWB proposes.
Give NASA a real challenge

On Wed, 31 Mar 2004 12:55:49 GMT, "Alan Erskine"
wrote, in part:

Another problem that may be extremely difficult to counter will be the
bordom that will occur during the coast period (to Mars and also on return).
How can the psychological problems that may result from this be countered?

I think that Dr. Zubrin is correct when he largely dismisses this
problem. However, because of the expense of a Mars mission, no
possible source of risk should be overlooked.

One thing that would help is to provide the astronauts, on DVD-ROM,
extensive libraries which they can play back on personal computers.

Given that life support is a problem, perhaps just send two astronauts
to Mars, a husband-wife team.

John Savard
http://home.ecn.ab.ca/~jsavard/index.html

Alan Erskine ) wrote:
: 1. Flight time - this can be overcome with an increase in escape thrust -
: either a large chemical rocket or nuclear/electric as suggested by Tom
: Stafford at the President's Commission on Moon, Mars and Beyond conference
: (February 11, 2004 - Washington, DC). Nuke/electric has to be developed but
: there are even alternatives (using existing systems in new ways rather than
: new systems).

: 2. Communications - Apollo had a ~3 second round-trip for comms. Mars
: has nine minutes - 180 times longer. Mars is also going to be on the
: opposite side of the Sun for a long time - how do you communicate
: through/around the Sun?

I have been thinking about this recently. Could we put a comm/relay sat in
"polar" orbit around the sun? Its period would be something that would
have it away from the ecliptic when we are at superior conjunction with
Mars. I think a period of 195 days would do. That is 1/4 the synodic
period of Earth/Mars. That puts the orbit inside Venus' orbit, but going
north and south as opposed to east and west as do the planets for the most
part.

Eric

: 3. Systems reliability - because of point 1 and 2 and also for this
: reason: With Apollo 13, the crew would only have had to remain in their
: pressure suits for 4-5 days - going to Mars, the crew would have to remain
: in their suits for 100 or more days if there was no pressurised environment.
: Pressure hull integrity will be of paramount importance. Yes, there are
: systems that can be used to seal a leak (ISS has something as I recall), but
: what if the pressure leak isn't detected (ISS pressure is monitored from the
: ground).

: Feedback please.

: --
: Alan Erskine
: We can get people to the Moon in five years,
: not the fifteen GWB proposes.
: Give NASA a real challenge
:

Alan Erskine ) wrote:
: Another problem that may be extremely difficult to counter will be the
: bordom that will occur during the coast period (to Mars and also on return).
: How can the psychological problems that may result from this be countered?

Wait, the movie "Red Planet" had the answer. Make sure tha astronuats look
like Val Kilmer and Carrie Ann Moss.

Eric

: --
: Alan Erskine
: We can get people to the Moon in five years,
: not the fifteen GWB proposes.
: Give NASA a real challenge
: