"Why Haven't We Gone To Mars Yet?" Asks Robert Zubrin

[Sturgeon]

OK, maybe this is unfair to Robert Zubrin, but here's my drunken, late-night ranting on WHY HAVEN'T WE GONE TO MARS? WAAAAAH.

Ready for the short answer? OK: It takes a fucking long time to get to Mars.

(hopefully not too) Long answer:

Many people thought the Mars landings would be the natural follow-on to the epic Lunar landings of the late '60s and early '70s, and they weren't necessarily wrong. I still feel the Mars landings are a natural follow on, but there are some reasons besides shinking budgets, a loss of romance, and ennui that I feel are worth examining. I am not an expert, and I welcome anyone who is stepping in and telling my I am wrong, but I will nonetheless do my best to get this stuff right.

 

So, it might feel like a Mars mission would be just like a Moon mission, but with a bigger rocket and maybe a habitat and stuff, right? Well, that's accurate, but it's not everything. I don't claim to know everything about a Mars mission, but here's some stuff to think about. 

First, we have to understand that a hypothetical Mars mission is not like a hypothetical Lunar mission, and the most important differences have nothing to do with Mars itself! A trip to the Moon takes about three days. Coincidentally, a human can survive about that long with no resources whatsoever except air. This means that a Lunar mission needs to take along on-board supplies lasting for six days, and oxygen for six, and that's enough for the mission plus contingency. Now, the important part here is that the Lunar mission doesn't need to develop any living techniques to complete its mission. Simply, they can easily bring along what they need to survive.
 

For a Mars mission, it's several orders of magnitude more complicated. The mission takes a minimum of 130 days one way, if you have awesome high speed rockets. More realistically, 260 days is your one-way trip. That's close to 9 months of travel there, then 9 months back. Asking "how much weight of supplies would you need to supply one human on that trip?" is so complex as to be almost meaningless. Let's look at just water. A human needs several quarts of water per day to survive, just to drink. So for 260 days, one person would need about a metric ton and a half of water. That's for hydration alone, and more would probably be needed. It would be difficult to calculate exactly the delta-v needed to move a steadily-venting metric ton point five of water to Mars and back, but this alone represents a problem.

Can you do a Mars mission via supply alone? Clearly you can theoretically-speaking, but consider that the weight of daily supplies needed for a Mars mission would be 87 times that needed for a Moon mission, and then recall the size of the Saturn V rocket that took us to the Moon. Then add in the weight of ancillary supplies like medicine, etc, that would be needed because a Mars mission can't just abort. Being on a spaceship halfway to Mars is the remotest man has ever been by well over three orders of magnitude; a doctor in Antarctica by comparison has instantly available help. 

 

This is all to say a Mars mission has to be a self-sustaining ecosystem, barring mind-boggling available delta-v and awesomely huge launch vehicles with which to launch a tremendous amount of supplies. One hundred and twenty man-months' worth of MREs and water doesn't seem like such a big deal until you see how big the rocket(s) needed to take it to Mars and back have to be.

So we've recharacterized the problem. Clearly, getting to Mars isn't so hard. We've visited it by proxy loads of times. But now we realize that those probe missions weren't NASA just dicking around, they were actually dramatically lower intensity than a supplied Mars mission. To bring humans to Mars, we need to replicate the human ecosystem, and stick it on top of a rocket, or more likely in pieces atop multiple rockets. Replicating the human ecosystem sounds straightforward... Until you actually try it. This is Biosphere 2 (Biosphere 1 is Earth, yes, I know, nerds ruin everything):

 

Biosphere 2 was one of the first major projects in trying to replicate Earth's ecosystem apart from itself. I am not going to say that we learned nothing from Biosphere 2, but in the context of preparing for a Mars mission, Biosphere 2 did not result in a viable system for space exploration, so far as I can tell. For a start, Biosphere 2 is much, much too large to launch atop a rocket!

It sounds like I'm getting down on Biosphere 2, but I actually respect the effort quite a bit. It just isn't the result we need to get to Mars by 1995. However, there is another human habitation that has given us a much greater head-start towards a Mars mission than Biosphere 2:

 

 

Good ol' Alpha. I feel as though the public perception of ISS has been a little harder on it than it should be. A space station feels unglamorous. It doesn't feel daring, like stepping on the Moon was, and it doesn't feel dangerous or brave. ISS has gotten more popular in recent years, as its competition for the spotlight (particularly Shuttle) has faded, but it still never captured people's hearts like Apollo or even Shuttle did.

But really, ISS is kind of the Apollo 9 of the Mars effort. OK, that analogy doesn't go very far, but ISS is a crucial experiment - a long term one - in the process to going to Mars. We're putting people in space for very long periods of time, and seeing what exactly it is they need to survive up there. We now know exactly what technologies we need to perfect to supply and keep alive people during the twenty-month Mars mission, because we've already kept people alive in ISS for that and longer. And, we're making very significant strides:

To avoid getting into too much detail, and recognizing that I think I've made my point, I'll leave it there, adding one final thought. NASA is staffed by people who want to go to Mars. Every single person at NASA, from Charlie to the janitorial staff, probably hold as mankind's finest achievement the Apollo Moon landings, and they want to see that achievement topped by landing human beings on Mars. I would be willing to bet that NASA could get a direct order from Congress to in no way pursue a mission to Mars, and we would still make progress in deliberate, calculated, secret ways towards that goal. The perception (which I have been guilty of, too) that NASA is sitting on their ass and needs to get on with it, is probably less justified than we want to believe. Going to Mars will be hard, and there's no guarantee that we'll make it the first time. There are a lot of problems that need solved, a fuck ton of engineering to realize those solutions, and industrial quantities of bravery needed to execute them.

Putting people on Mars will be the greatest achievement in the history of mankind, until the next. Not because it is easy.
 

[Belesarius]

We're gonna need a big fucking ship. And it's gonna cost a shitton of money and be hard to do.  I think, realistically we need viable cargo SSTO before we'll get there.

[Toxn]

From a habitation perspective; it's interesting that we don't even know if the radiation flux received on the trip out (let alone once you land) will cause problems:

http://www.space.com/24731-mars-radiation-curiosity-rover.html

http://news.uci.edu/health/long-term-galactic-cosmic-ray-exposure-leads-to-dementia-like-cognitive-impairments/

 

The worst case scenario here is that your astronauts don't even make it to the red planet before becoming permanently brain-damaged by cosmic ray exposure and the like.

 

Also: Earth-2 needs more love simply for demonstrating that we have no working theoretical foundation for designing contained ecosystems. We know effectively nothing here.

[SuperComrade]

Just need to get that EM drive working

[LostCosmonaut]

Personally, I think before going to Mars, we should establish a long duration (>3 months) colony on the moon for several reasons;

 

• It would allow us to practice operating in a closed biosphere on a planetary(ish) surface.
• It would give data on the effects of low levels (but greater than zero) gravity on the human body for extended periods.
• The lunar regolith contains water and other valuable resources (especially in the polar craters), so in situ resource utilization techniques can be refined.
• It's only three days away, so the astronauts/cosmonauts won't be completely boned if something goes wrong, as they might be if help was nine months away.

[LostCosmonaut]

Don't worry, guys, Robert Zubrin has the transit time issue covered; this will totally work.

[Sturgeon]

<p>

Personally, I think before going to Mars, we should establish a long duration (>3 months) colony on the moon for several reasons;

• It would allow us to practice operating in a closed biosphere on a planetary(ish) surface.
• It would give data on the effects of low levels (but greater than zero) gravity on the human body for extended periods.
• The lunar regolith contains water and other valuable resources (especially in the polar craters), so in situ resource utilization techniques can be refined.
• It's only three days away, so the astronauts/cosmonauts won't be completely boned if something goes wrong, as they might be if help was nine months away.

Bob scoffs at your silly, meaningless "flags and footprints" plan.

Unfortunately, yes, he actually does.

[Donward]

Short answer?

Hippies.

In the 1970s there were complaints about the cost of the lunar missions with the usual bullshit about for the price of an astronaut hitting a golf ball on the moon, we could buy an arbitrary number of school books. You even had pop culture complaining with "Meathead" in the TV show "All In The Family" making a similar complaint.

[Sturgeon]

Wow, I really drunk farmed upboats with that one, didn't I?

[Sturgeon]

We're gonna need a big fucking ship. And it's gonna cost a shitton of money and be hard to do.  I think, realistically we need viable cargo SSTO before we'll get there.

 

I'm gonna shit on your parade here, because SSTOs are really dumb.

 

Cheaper heavy lift is coming, that being the primary effort of launch vehicle developers, but single stage to orbit is just on the wrong side of the rocket equation, and I think the only reason people keep hammering at that nail is because they want SPACESHIPZ FWOOOOM ZOOOOOOM NWRAAAAAAAAW PEW PEW PEW. I'm not mocking you, Bele, mind, but I think that's the primary reason developers keep looking at SSTOs. They're not cheaper or better in any way, and any technology that makes an SSTO feasible makes a multistage rocket AMAZING.

[Sturgeon]

Don't worry, guys, Robert Zubrin has the transit time issue covered; this will totally work.

 

This is that engine design that you presented to your nuke prof and he was all GET OUT OF MY SIGHT!

[Zinegata]

Bob scoffs at your silly, meaningless "flags and footprints" plan.

Unfortunately, yes, he actually does.

 

The main problem with the Moon Base people is that they keep touting it as a literal stepping stone to Mars - as in build a moon base and then use that to launch a mission to Mars.

 

The Delta V just doesn't work that way, at least based on Ecklund's game-ified system (which I assume is pretty accurate since Ecklund consulted Zubrin for the Delta V map). It is much more efficient to have something from Earth orbit go to Mars rather than from the Moon.

 

As a test bed for out-of-Earth colonies, the Moon is fine. It might even be a possible resource extraction point to send stuff to Earth orbit to make the Mars mission rocket with (although it's probably more efficient to mine Phobos/Deimos and sling the resources back to Earth). But as a literal launch pad? That's what drives Zubrin nuts.

[Sturgeon]

...What gaggle of drooling idiots wants to use the Moon as an airstrip for a Mars mission?

Not doubting they exist, but that one is new to me!

[LostCosmonaut]

I'm guessing most people just assume that Moon->Mars deltaV = Earth->Mars - Earth->Moon. Although, tbh, I've not yet encountered anyone seriously proposing it (though I haven't really looked very hard).

[Sturgeon]

I assume such stupidity comes by way of analogy to the UK being a staging ground for invading Europe in WW2, or something like that, but the problem is that this makes no sense to anyone with two brain cells to rub together who isn't also a member of the press. Here's why.

First, even if what you said was true, if dv(Moon;Mars) = dv(Earth;Mars) - dv(Earth;Moon), then why the fuck would you stop on the Moon anyway? Your delta-V requirements are identical whether you go from Earth;Mars or Moon;Mars. After all, you have to send all the stuff Earth;Moon in the first place! This even assumes that this hypothetical idiot doesn't know that going up and down on the Moon actually costs delta-V.

Further, what is there on the Moon? It's not like stopping in Atlanta on a flight from Baltimore to Dallas, the Moon doesn't have food, fuel, etc, unless you put it there on the first place. Sure, if Luna City were already well and constructed on the Lunar surface, then yeah, maybe in the hypothetical This Is Not How Plantetary Physics Works idiot brain-model, you might stop off there for gas or whatever, but it doesn't.

Finally, any idiot who's seen Apollo 13 should know that folks in Lunar orbit or on the Lunar surface are at a great risk, being days away from help. Why bother with all that when you can just build the damn spaceship in LEO?

[Collimatrix]

If you could harvest resources off the moon it might be sensible.

 

Not sure what you'd use there for propellant.

[LostCosmonaut]

I suppose you could make LH2/LOX from any ice deposits of water in the regolith. I think Atomic Rockets also mentions that you can make some kind of aluminum based propellant using lunar materials, but that would probably be very low isp.

[Sturgeon]

If you could harvest resources off the moon it might be sensible.

 

Not sure what you'd use there for propellant.

 

 

I suppose you could make LH2/LOX from any ice deposits of water in the regolith. I think Atomic Rockets also mentions that you can make some kind of aluminum based propellant using lunar materials, but that would probably be very low isp.

 

Yes, if you already had a Moon base capable of harvesting resources. We do not.

[Collimatrix]

Yes, if you already had a Moon base capable of harvesting resources. We do not.

 

And whose fault is that now?

[Khand-e]

And whose fault is that now?

 

I thought it was well established Dick Cheney and his cabal of cronies that hate good military ideas already have one?

[Sturgeon]

And whose fault is that now?

 

Earth's gravitational pull?

[Zinegata]

...What gaggle of drooling idiots wants to use the Moon as an airstrip for a Mars mission?

Not doubting they exist, but that one is new to me!

 

 

The Internet. Do note that most folks aren't even aware what Delta V is.

[Zinegata]

If you could harvest resources off the moon it might be sensible.

 

Not sure what you'd use there for propellant.

 

The most efficient harvesting site may in fact be Deimos, rather than the moon, since it costs less Delta V to get water from Deimos to LEO in specific windows than resources from the Moon to LEO. Really someone ought to try an automated water-mining mission there to send water ice to LEO; as this would greatly reduce the amount of water that needs to be lifted from Earth and may allow for more extensive industrial experiments be done in space stations.

 

Well, that is unless of course we install a space elevator in the moon... but that really implies a pretty extensive moon base at this point.

[Donward]

And whose fault is that now?

Hippies. I've already said this. Does no one remember the 1970s and the absolute shithole that was Washington DC politics at the time?

[LostCosmonaut]

And whose fault is that now?