
Confronting the Credibility Gap for Crewed Exploration of Mars - apsec112
http://caseyexaustralia.blogspot.com/2016/09/mars-society-talk-confronting.html
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Animats
Landing is really hard. Not enough atmosphere for aerobraking, and too far
from home to have enough fuel for a powered landing. It's a fuel problem.

There's the expensive approach. Send multiple unmanned tanker ships into Mars
orbit and have them rendezvous into an orbital supply depot. Send landing
tanker ship to rendezvous with them and refuel with enough fuel for a powered
landing. Landing ship descends. Repeat to build up fuel reserve on Mars
surface. Manned ship then docks with orbital supply depot and crew switches to
lander. Lander descends, lands near fuel reserve, and refuels for ascent.

Ascent is to Mars orbit and docking with the orbital supply depot. Crew
switches back to long-haul ship, refuels it, and goes back to Earth.

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jcoffland
How about we harpoon Mars and pull down one end of a space elevator?

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pilom
The biggest problem with a space elevator on Mars is that the orbit of one of
its moons is closer than the minimum height of a space elevator to be stable.
Eventually the elevator cable will get hit.

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dTal
Hang the cable from the moon and let the end trail?

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Daneel_
If you'd prefer to watch it, Casey's talk is available on Youtube:
[https://www.youtube.com/watch?v=c0a7eR8Wi4Y](https://www.youtube.com/watch?v=c0a7eR8Wi4Y)

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nickparker
There's a very enjoyable discussion in the comment section with my (brilliant)
former colleague Max Fagin. He points out that Casey's first draft of this
post neglects the curvature of Mars, and when you account for it Casey's model
predicts the craft punching out the other side of the atmosphere.

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aedron
Can't see those comments. Were they deleted?

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chandmer
They're on the ITS post.

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jcoffland
Radiation is a huge problem. Both en route and on Mars.

A lot of these problems beg the question. Is Mars really the best target? Sure
it's close but there are moons around Saturn that are interesting as well.
Titan for example. Sure it's cold but it has a lot of atmosphere. Presumably
landing would be easier. If we could learn to live underwater we could
possibly visit Ganymede or Europa.

~~~
semi-extrinsic
Radiation, as you mention, is a very big problem which is independent of
destination.

Human psychology is another, perhaps even bigger problem, also independent of
destination. We've had various experiments with prolonged isolation, but none
where the subjects _know_ that they're never coming back to Earth. I'd say
psychology has a >50% chance of wrecking the first manned missions to other
planets/moons, unless we send huge ships with hundreds of people.

In the Red Mars trilogy by Kim Stanley Robinson, the author has come to the
very astute observation that

a) no perfectly rational, mentally healthy human would volunteer for such a
mission

b) there will necessarily be extensive psychological screening to ensure we
only send rational people

thus c) the people who will be selected are likely to be non-rational actors
very good at concealing their non-rationality from psychologists. Also known
as people with psychopathic tendencies.

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coldtea
> _Human psychology is another, perhaps even bigger problem, also independent
> of destination. We 've had various experiments with prolonged isolation, but
> none where the subjects know that they're never coming back to Earth._

Who said they're never coming back to Earth?

> _no perfectly rational, mentally healthy human would volunteer for such a
> mission_

That's an easy problem to solve, as there are no "perfectly rational" and/or
absolutely "mentally healthy humans", and have never been anyway.

And people can still be quite rational and mentally healthy and yet cherish
the possibility to take such a mission, even if there's a possibility to die,
etc.

In fact, it's needs no more troubled people than those that go to the army and
are OK to be sent to war, or people that dive and explore the oceans, etc etc.

~~~
semi-extrinsic
How are they going to come back? All realistic plans I've seen are for one-way
trips.

The thought of dying isn't the inherently problematic part, but rather the
extreme isolation. People who go to war are there for only some months and
have plans for going home, back to friends and family. People who dive and
explore the oceans are isolated for a few days at worst; perhaps months in a
nuclear sub, but there you have already a pretty large crew around you.
Compared to decades spent isolated with a handful of people, and no return
ticket to the rest of humanity, those are nothing.

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coldtea
> _How are they going to come back? All realistic plans I 've seen are for
> one-way trips._

Huh?

" _The first crewed Mars mission would be expected to have approximately 12
people, with the primary goal to "build out and troubleshoot the propellant
plant and Mars Base Alpha power system" as well as a" rudimentary base." In
the event of an emergency, the spaceship would be able to return to Earth
without having to wait a full 26 months for the next synodic period._"

[https://en.wikipedia.org/wiki/Interplanetary_Transport_Syste...](https://en.wikipedia.org/wiki/Interplanetary_Transport_System#Mars_early_missions)

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chandmer
Yep. The spaceship has to come back at the very least.

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robbiep
I had the pleasure of attending high school with Casey. He (and his brother as
well, who i worked under as a doctor) are both capital G geniuses. Anyone
wanting to be highly informed on interesting topics like the hyperloop (with
his potential biases due to involvement with Hyperloop one), terraforming,
space travel or other similar things would do well to follow him on quora.

~~~
chandmer
That's too kind! Say hi on fb some day.

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kirrent
ITS is conspicuously absent in this post but has been discussed by the same
author in another post.

[http://caseyexaustralia.blogspot.com.au/2016/09/spacex-
mars-...](http://caseyexaustralia.blogspot.com.au/2016/09/spacex-mars-plan-
analysis.html)

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james-watson
What gets forgotten here, and something that I keep bringing up, is the lack
of a Martian magnetosphere. This means long term human settlements have to be
artificially shielded.

This means living underground, which defeats the point of going to Mars in my
opinion. Elon mentioned using a local magnetosphere generator, which is one of
those ideas that is theoretically possible but whose practicality seems
questionable. How powerful a magnetosphere generator is required to deflect
ionizing radiation? How much power generation capacity will a Martian colony
have to spare? Will this require a Fusion reactor?

The only hope I have for Martian settlement is that Musk and his engineers are
some of the most audacious and brilliant people on the planet. I will never
bet against their success, and I wish them the best of luck.

I have been a space exploration fan since as long as I can remember, I just
worry that humans have a tendency to focus on the wrong goals when ideals and
emotion cloud our judgement (e.g. the Space Shuttle).

~~~
LeoDox
Mars has an iron core; it's just not molten which prevents it from being
ferromagnetic.

I have three questions:

1\. Is it merely a question of mass? That is, if Mars were larger would the
increased gravity increase pressure at the core and keep it molten?

2\. If it IS merely a question of mass, is there any way to add mass to Mars
which doesn't disturb its orbit? Because if you could, then you simultaneously
solve both the problem of low gravity AND lack of magnetosphere, which
together solve the problem of maintaining atmosphere. Basically the whole
planet becomes extremely Earth-like

3\. If increased mass wouldn't necessarily wreck its orbit, could something be
done to "steer" asteroids from the Main Belt into collision courses with Mars?

I really don't know anything about orbital mechanics so maybe there's an
obvious flaw in this (aside from the energy required to reroute that many
asteroids).

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nine_k
The amount of energy required to lower the orbits of enough asteroids (e.g.
20% of Mars total mass) is probably enough to melt a significant portion of
Mars. Unfortunately, collisions would mostly heat up the surface, not the
core. Even if you could precisely deorbit enough asteroids to hit Mars, the
results of the bombardment would probably take a long time to settle.

Planetary-scale engineering is not only hard, it's inevitably slow.

I think cleaning up the atmosphere of Venus by spreading CO2-eating anaerobic
air-suspended algae is more realistic, and the results would likely be nicer.

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avmich
The document linked at the end of the talk currently contains summary
regarding the radiation problem on the way to Mars.

I've heard of the following approach. The spacecraft generates a magnetic
field which spreads around it in flight, having some substantial size (order
of kilometers). Relatively small amounts of matter (some gas) are constantly
emitted from spacecraft, get ionized and trapped in the magnetic field. Such a
low density thick "cushion" of ions makes the radiation shielding.

I'd like to learn more about effectiveness of such an approach.

~~~
Symmetry
You really want to be piling some dirt on top of your shelters for pressure
containment reasons anyways.

~~~
avmich
That idea was for travel time, not when the spacecraft is already landed on
Mars and the crew want protection on the surface. There, dirt will help, but
in flight there is nowhere to get it from.

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brilliantcode
Why Mars though? Why not build a lunar base on the moon? Maybe even a hotel on
the moon, I'm sure people will enjoy watching earth from the moon.

I just fail to see this obsession with Mars. We don't even have manned landing
on Mars and we are already having questionable stuff like "Mars One"

And finally (one for the conspiracists): nearly 50 years ago we landed on the
moon without any of the technology we have today. Why hasn't there been any
strides? Shouldn't it be cheaper to go to the Moon vs Mars? Shouldn't it be
possible to colonize Moon more easily and faster than Mars?

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woah
I think part of it is that mars has an atmosphere

~~~
dTal
An atmosphere that provides none of the benefits of appropriate pressure,
temperature and gas mix but all of the challenges of weather and airborne
dust.

~~~
namlem
The martian atmosphere does have the benefit of having created much less
abrasive dust over the years. Moon dust causes much more wear to moving parts.
Mars also has accessible carbon, which the moon does not. The martian
atmosphere can supply plants with the CO2 they need, enabling agriculture.

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sjbase
Is a no-return mission something worth considering, on a purely technical &
logistical level? Has anyone seen a really good analysis of this?

My sense is that the social, political, and psychological barriers could be
overcome for such a thing.

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gurneyHaleck

      "Do you realise the astronauts 
       will run out of nitrogen on day 
       59 and die?" 
    
      So Mars One isn't really funny, it 
      has probably set back the credibility 
      of the movement by a decade. 
    

I realize it's not meant to be a truly quantifiable statement, but I'm always
curious why people regard incidents like this as producing serious damage to
progress.

There are definitely crucial moments in political science, when an absurd gaff
completely botches a carefully crafted image, completely imploding the efforts
of hundreds of people, and sinking an entire team permanently. Cringey things
that seem to matter to the echo chamber of a 24 hour news cycle.

But I don't feel like hard science works that way. When it comes to real
engineering feats, if one company tries to trade on faulty calculations, and
their charade is laid bare, the smoke and mirrors disappear only to reveal the
same bald truth that had always been there from the start: hard problems defy
shenanigans.

A political failure doesn't deflate an engineering problem. Not in the same
way it deflates a PR campaign. If the hard science was not respected, then
there was no investment in a decade of progress to begin with.

So, these swindlers then maybe blew a decade of real funding, only to burn
their investors with bogus project plans and proposals, ripping off charity
and fomenting skepticism and suspicion? I think skepticism in this sphere is
actually healthy, and separates the children from the adults.

Waste is a bad thing, and maybe real money disappears, but maybe that kind
money came from the kinds of people who might have just as soon blown their
cash on personal assistants, vacations and clothes. Clearly such investors
were not "buying science," or they'd have known better.

So, then the only thing left is that maybe there's the premise that admirers
of the charade would not have loitered on the sidelines, simply yearning to
lend their support to the parlour trick they were true believers in. That they
would have stepped up to the task, had they known progress was stalled. I
don't buy that.

No matter what, I don't think there has even been a decade of effort spent on
crewing a mission to Mars. It's all been so much conjecture. It's never seemed
to be an easier idea than an underground moon base, and no one seems to be
giving lunar round-trips or installations much more consideration than mars.

Space shuttle accidents and launchpad explosions cast the true hazards in a
much more severe relief, but knowing that people are even trying and failing
feels like much more significant progress than a lot of talk and faulty plans.

So was there really any "damage" done by some of these PR goof ups?

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fapjacks
"And then you have the EM/reactionless drive, which is less efficient than a
Hall effect thruster, and also impossible."

I could sense this was coming, and I stopped reading here.

~~~
chandmer
Sorry to come across as grumpy. It wasn't really the venue or topic to argue
about exotic propulsion. There are many excellent resources online explaining
why EM cavities are reactionless. You can write down the Poynting vector and
then use Green's theorem, it's a neat result. With dire consequences for wish-
powered spacecraft. -C

~~~
james-watson
Don't be sorry. We need scientists to be skeptics when it comes to absurd
assertions which violate the most fundamental principles of physics.

Extraordinary claims require extraordinary evidence.

~~~
fapjacks
There's actually a difference between being skeptical and calling this thing
-- with peer-reviewed research[0] -- "wish-powered".

[0]
[http://arc.aiaa.org/doi/10.2514/1.B36120](http://arc.aiaa.org/doi/10.2514/1.B36120)

