2013 marked the first time that
women made up 50% of the NASA
astronaut candidate class.
But looking forward, should
NASA try to go even higher?
Should the first human
Mars mission be all women?
Look, it's no secret that
we here at "Space Time"
love the idea of
cloud cities on Venus.
But unless our #OccupyVenus
Twitter campaign
works miracles,
humans will probably
end up going to Mars first.
The question is, which humans?
See, several articles in
journals or in the press
have asked whether it might
make sense for a Mars crew
to consist mostly or
even entirely of women.
It's an interesting proposal
that warrants discussion,
but we need to get some
facts straight first.
Today, I'm going to review
some of the data underlying
the various arguments.
You guys ready?
All right.
Let's start with the
physiological arguments
for all-female missions
beyond Earth's moon.
A lot of us want to become
astronauts, but let me tell
you, becoming one is not easy.
Lots of factors
disqualify you from NASA
before you even begin including,
currently, height restrictions.
You've got to be 4'11 to 6'3.
That's it.
In all likelihood, scrutiny
will be even greater
for the first
manned trip to Mars,
because we can't have these
pioneers falling apart
200 million miles from Earth.
So physiologically, what's
the biggest health concern
for astronauts right now?
Well, according to
a 2014 NASA study
that we link in the
description, it's not bone loss.
Instead, it's an
issue where women
appear to have a big
advantage-- vision impairment.
Several male astronauts
have experienced
confirmed vision problems,
often accompanied
by anatomical
changes to the eye,
both during and
after space flight.
All of them were in
orbit six months or less,
which is a lot less
time than the eight
months of zero G
in each direction
that you'd have
on a Mars mission.
Now, countermeasures
are being studied,
but it's tough, because the
exact cause of the phenomenon
isn't entirely understood yet.
What we do know is that so
far no women have experienced
lasting vision issues.
And since vision is a pretty
critical faculty on a Mars
mission, and given the
uncertainty about underlying
causes, this might be a major
checkmark in the pro-all women
column.
So are there physiological areas
where women do worse than men?
Sure.
Let's look at the
same NASA study.
Women are more prone to space
motion sickness when they first
hit zero G, but that goes away.
Women get more urinary
tract infections,
but that can be treated
with antibiotics.
And women faint more easily
from standing up too fast
once they get back
to Earth, which
may not be as big a deal
in Martian gravity-- still
unclear.
Now, none of these rise
to the same mission
critical level as
impaired vision.
However, women do have
another physiological minus
that does have to be
considered-- radiation.
Women have about twice
the risk of radiation
induced cancer that men do.
It's why NASA allows
women only half
as much lifetime space
flight as it allows men.
Radiation would be a
big issue for a Mars
mission, no question.
However, given current
shielding technology,
even men might exceed the
allowed radiation safety
levels.
So while it's a
negative for women,
radiation risk might
be one of those things
that you have to solve
for everyone in order
to send anyone.
Anyway, absent to test
for or countermeasures
for the vision
problems, women may
have a physiological advantage
just because of that.
OK.
What about psychological
suitability?
Well, the same NASA study
reports no sex-based difference
in psychology or behavior
during spaceflight.
They attribute this to the
robust screening and training
that NASA astronauts undergo.
However, other sources
and space programs
tend to give women the
edge in this category.
For example, the British
newspaper "The Guardian"
reported Chinese space
officials as saying
that their female astronaut
candidates exhibit better
communication skills and
adapt better to isolation
than the male counterparts.
Similar results were found
during testing of the Mercury
13.
That's a group of
women who were put
through the same tests as
the male Mercury astronauts
back in 1960.
Incidentally, the
story of those women
and the subsequent
political battle
to try to have women admitted
to the US astronaut corps
is fascinating.
It's covered in an episode of
the PBS "Makers" series, which
I highly recommend.
There's a link to the
video in the description.
Anyway, it looks
like women might
have a slight psychological edge
on longer duration missions.
But let's suppose that nothing
we've said so far were true.
No physiological or
psychological edges for women.
There's still another
argument for preferring women
to men on longer
space missions--
namely that it costs less to
send them to other planets.
How come?
It's about food.
While you can recycle
air and water,
you need to take all
the food mass with you
on a trip to Mars.
And that's true even if
you manage to grow plants.
Now, it turns out that
women need less food
to do the same activity
as men, so that
means less mass to transport,
less propellant, and thus
lower cost.
Now, this argument has been
made many times over the years,
including by some
NASA employees.
But it got a lot more
attention in late 2014
when writer Kate Greene wrote
an article to this effect
in "Slate."
Greene was one of
six volunteers--
three men and three women--
in the first four months
study at High Seas, a
NASA-funded, enclosed, isolated
habitat on Mauna
Loa in Hawaii that
simulates aspects of
conditions on a Mars mission.
Greene noticed that the women in
her cohort consumed about half
as many calories as the men,
despite comparable activity
and exercise.
This was consistent
with what had
been seen earlier by current
and former NASA analysts
that she cites in her article.
But what Greene doesn't give us
is an actual numerical estimate
of the savings, so I
did some rough math.
Let's consider the long
version of a NASA Mars mission.
It would be 910 days round trip
with over a year on the Martian
surface.
For whatever reason,
the calorie requirements
in space and on Earth
are basically the same.
So taking into account the water
you need to rehydrate the food,
each person would eat about
a kilogram of food per day.
That's about 1,000
kilos, or one metric ton,
per person for the round trip.
So how much food mass could
you save if you used all women?
Well, the crew would
probably be four people,
but let's say six
just to high-ball it.
That's six metric tons of food.
I'm assuming our
comparison baseline
is three men and
three women, replacing
all the men with women.
Since my one kilo a day is
an average of both genders
and since we're only replacing
the three men with women--
that's half the crew-- you
can knock out about a third
of your total food mass.
So our savings would
be two metric tons.
So how does that mass savings
translate into dollar savings?
To ballpark that you need to
work out how much fuel it would
take to get that food from Earth
orbit to Mars orbit and back,
and then estimate
the cost of getting
the food plus all that
fuel off of Earth's surface
to begin with.
Now, I worked out that you need
about 50 tons of propellant
to move those two
tons of food there
and to bring back the
half ton or so you'd
need for the return trip.
Why so much?
Because as you add fuel
to move your payload,
you then need to add
fuel to move that fuel
and so on and so on--
this is why space flight
costs so much money.
Now, my number is conservative.
I assume that we wouldn't
need any fuel for the descent
to Mars, that you'd leave
all the food for the return
trip in orbit around Mars, and
that you'd leave all your waste
down on the Martian surface.
So what's the dollar savings?
At today's launch prices, it'd
be between $0.5 billion and $5
billion.
Our 50 metric tons of
food plus food fuel
would thus represent around
5% to 7% of the mission mass
and 5% to 7% of the launch
cost, which might be 0.5% to 1%
of the estimated
total mission budget.
That's not crazy, but it's not
entirely negligible either.
Now, granted, launch costs are
dropping so these projections
could change.
But even if SpaceX manages to
get those launch costs to 1/10
of what I've quoted,
we're still talking
a savings of hundreds of
millions of US dollars
if we sent only women.
So I guess my bottom line
question to all of you is this.
Suppose it turns out that by the
time we're ready for the Mars
mission we can manage radiation
but cannot manage the vision
issues.
And suppose that
further testing shows
that four to six women locked
in a tiny can in a black void
for two to three years
would work as a team
with lower risk of flipping
out as well as or better
than a mixed sex crew would.
If all that turns out to be
true, and taking into account
the cost issues we discussed,
should an all-female crew
be given preference for
the first Mars mission?
Because remember, the
first Mars mission
really needs to succeed.
So it seems, to me at least,
prudent to eliminate every risk
that you know about
and are able to manage.
But let's see what
you guys have to say.
Have at it in the comments, and
feel free to point out anything
that I missed or got wrong.
I'll report on the evolving
discussion on the next episode
of "Space Time."
Last week we asked what the most
realistic artificial gravity
in sci-fi is.
You guys had a lot of
really great comments.
If I don't get to yours
individually, don't feel bad.
We have limited time.
A lot of you brought
up sci-fi series
that I did not mention
in the episode.
Let me run through these things
in order. "Ender's Game."
I agree that the novel
seems pretty realistic,
the movie less so.
But since I don't
have any numbers,
I have no way to confirm
this. "Interstellar"--
guess what, I haven't
seen the movie yet
because I have no life.
But I looked at the
specs, and the ship
rotates at five to six RPMs.
You would definitely
notice a Coriolis force.
"Rendezvous With Rama,"
which is another novel
by Arthur C. Clarke.
I agree it has slow RPMs
and low Coriolis effects,
but it only has 0.7 earth Gs,
which might be intentional.
I don't know.
The "Gundam" anime series-- yet
something else I've never seen.
However Scina Bocere
pointed out that its design
is based on something called
an O'Neill Cylinder that you
can look up on Wikipedia.
And Watchit1337 supplied numbers
for the "Gundam" ships, which
if right, I agree would produce
minimal Coriolis effects.
Thumbs up.
Finally, some people
brought up using
an accelerating ship in order
to get artificial gravity.
So go 9.8 meters per second
per second acceleration in one
direction.
This is done apparently in "Mass
Effect," the "Expanse" series,
another Niven work called
"The Mote in God's Eye."
The problem is, where
do you get the fuel
to keep that acceleration going?
There's lots of reasons
that's not realistic, which
is why I didn't bring it up.
The remaining comments
are about things that
happened in the episode itself.
Greg Peden points out that
around three minutes, 47
seconds, where we had the
ball sort of being thrown away
in the carousel, it
shouldn't go as straight
as we had it in the video.
It should tilt slightly to the
right because of the already
tangential momentum that it had.
You're absolutely right.
I'm glad you guys
picked that up.
Davide Conte asked why we
didn't bring up gravity gradient
effects, namely that in a small
ring-- this is not as a big
a problem in large
rings-- there would
be a gravity differential
between what you'd feel
at your feet and your head.
I didn't bring this up
because we don't entirely
know the effects of that.
There might be fluid
redistribution in the body,
and you might get more
bone leeching in your neck
because there's less gravity
there compressing your spine.
But in the short term,
the Coriolis effects
are a lot more significant.
Fortstorm asks, wouldn't
a rotating stations
have trouble turning because its
angular momentum vector would
have trouble being shifted?
He's hearkening back to our
barrel roll episode there,
and the answer is yes.
That's why O'Neill Cylinder,
which I've already referenced
in the comments, would have two
counter-rotating sections, so
that there would be gravity
here and gravity here
but no net angular momentum, and
thus no net gyroscope effects.
Excellent question
Thomas Archuleta points out
another scene from "Babylon 5"
that I remember in which Michael
Garibaldi drives a motorcycle
at a pretty fast clip
but doesn't seem to have
any weird Coriolis effects.
The reason is that
if he's driving
along the axis of
the space station,
there would be no
Coriolis effects.
The Coriolis effects
would only be there
if you move along the
rim, not along the axis.
CGIAgent asks, in a rotating
ship like "Babylon 5," assuming
that you had atmospheric
pressure at the rim
and that atmospheric pressure
dropped with altitude,
would there be some point
near the center of the rim
where the atmosphere got so
thin that you'd suffocate
and there'd be a
suffocation zone?
I think that would
depend on the specs
and how air was being
blasted in there.
You might be able to have
something on the axis
to sort of inject more air
out and artificially increase
the air pressure there.
But I don't actually know.
I'd be really interested
if you worked it out.
Finally, John Nielson,
who really likes the show,
says he doesn't know
what to do with himself.
May I offer the following
humble suggestion?
Spread the show.
Tell your friends.
The more people we get
watching, the better
we can make "Space Time."
