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In Robert Zubrin's December
lecture the excitement in the large crowd was palpable. He presented the
Mars Direct concept, a way of sending humans directly from the surface
of earth to the surface of Mars for orders of magnitude less cost than
NASA originally envisioned for the Space Exploration initiative. In
addition to the boldness and vitality of the concept, the quip meter
gave a high reading throughout the talk, unusual for an astronautical
engineer.
Zubrin began his talk with a look back in
history to the search for a Northwest Passage to Asia through North
America. Roald Amundsen and a crew of six in the 70 foot, 47 ton Gjva
was the first to succeed. There had been a hundred previous failed
attempts, all involving at least an order of magnitude greater effort
than the success. The British Navy, at the height of its power and
funded by the (at the time) wealthiest nation in the world, tried thirty
times without success. The Franklin expedition, with two specially
adapted steam frigates of 340 and 370 tons displacement and over a
hundred men had one of the deepest penetrations into the passage. They
died to the last man of starvation on or near King William Island.
Amundsen's crew became fat as they wintered in the same place. What was
the difference? Carrying all provisions versus living off the land.
Amundsen hunted caribou for food and had good land transport in the form
of dog sleds to bring the meat back to the ship. Franklin carried an
enormous amount of provisions, including useless items such as fine
china, but this could not save him and his crew when they were stuck in
the ice too long.
While at Martin Marietta, Zubrin and his
coworkers came up with a way to "live off the land" on Mars. It is easy
to compare the Amundsen mission with Mars Direct and the Franklin
mission with the 90 day study developed by NASA for the Space
Exploration Initiative (SEI) proposed by President Bush.
The 90 day study produced a human mission
to Mars costing $450B and taking 30 years to complete. The transport
ship was 1000 tonnes [tonne = 1000 kg = 2246 lb, a little bigger than a
short ton]. This is approximately the cumulative total mass launched
into space by the US since 1975, leading to Zubrin dubbing it the "Death
Star." All of it was to be assembled in space from small pieces in a
"parallel universe "of space stations, hangars, etc. This plan died on
arrival when Congress got a look at it because of the time frame and
price tag.
The people who did the 90 day study were
individually highly competent, maybe even brilliant, but the collective
result was a real turkey. Why?? The study was done with a large group of
people from all NASA centers. In addition to going to Mars, the
participants also had to (consciously or not) come up with ways to
justify work from their center, or possibly even groups within a center.
The 90 day study ended up with every possible technology becoming
mission critical, so each center's work would be necessary. This is the
opposite of good engineering practice, where as few things as possible
are mission critical.
We can't go to Mars in 30 years. We can't
go to Mars in 20 years. The longest we can take is ten years, or people
will get bored, political coalitions will fall, etc. If JFK had said we
must go to the moon before 1990, we would not have been there yet. He
said before the decade is out --- and we did it.
So, Mars Direct was designed to use off
the shelf, or nearly so, hardware. Advanced technologies -- electric
propulsion, nuclear propulsion, pixie dust, or whatever, would be great.
We just don't have time to develop them in a ten year time frame. They
can be used in follow up missions and for colonization.
Another difference between the 90 day
study and Mars Direct is the use of a conjunction trajectory rather than
opposition. The opposition trajectory minimizes total mission time, but
also minimizes time on Mars, has greater propulsion requirements, and
puts the crew in zero gravity and the interplanetary radiation
environment for a longer time. It's only common sense to spend more than
a couple of weeks after all the effort of getting there. The Mars Direct
plan puts people on the surface for one and a half years.
But, the main difference for Mars Direct
is "living off the land, "the manufacture of rocket propellant from the
Martian atmosphere. This is what allows a mission to go directly from
the surface of Earth to Mars and back with a Saturn 5 class vehicle. The
technology to manufacture methane and oxygen from the carbon dioxide
atmosphere of Mars dates back a century. Martin Marietta built a
demonstration converter for $47,000 in a short period of time.
The Mars Direct program uses an average of
one Saturn 5 class launch per year. Two types of payloads are used. The
first launch is a combined fuel manufacture plant and crew return
vehicle (unmanned). Enough hydrogen is carried to manufacture the
required methane for the return launch, but this is a small mass,
allowing launch from Earth by a single heavy lift vehicle. It lands on
Mars and manufactures the fuel for the return. At the next launch window
in two years, an identical payload is launched along with a manned crew
habitation module. The crew spends a year and a half on the surface and
returns to Earth with the first return vehicle. This cycle can then
repeat as often as desired. Another key item is a rover running on the
fuel from Mars, corresponding to Amundsen's dog sleds and greatly
increasing the exploration area. Mars Direct may cost $20B compared to
the $450B of the 90 day plan, making it fiscally possible. It is also a
far more effective mission in terms of time on Mars and area
covered.
Zubrin concluded with a quote from William
Bradford of Plimoth Plantation, 1621, "... all great & honourable
actions are accompanied with great difficulties, and must be both
enterprised and overcome with answerable courages." Going to Mars is
difficult and dangerous, but the rewards are great. We need a new
frontier to maintain the vitality of our civilization.
After the lecture Zubrin autographed
copies of his recent book, The Case for Mars, which spells out the Mars
Direct plan in more detail.
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