And this is why I think that a manned Mars mission is not in the cards until we can get some serious non-chemical propulsion working, and possibly a space elevator.
Although “Orion” is a four-letter word in many places, there has got to be a better way than what we have now.
Why would the radiation between here and Mars be any worse than the radiation between here and the Moon? Or is it just a length-of-exposure problem?
A 1920s style death ray is incapable of emitting sub-lethal radiation. DUH!
The Earth’s magnetic field acts as a shield against cosmic radiation.
-Kris
Out to what distance?
I don’t remember…
Unfortunately, I don’t have the SciAm issue where I read about this anymore.
-Kris
It’s mostly a length-of-exposure problem. Although NASA was really lucky there wasn’t a major solar storm during any of the Apollo missions. The astronauts would have been toast.
The Earth’s magnetic field only shields astronauts in Earth orbit and even there, there’s an area over the southern Atlantic Ocean where the shielding isn’t so great (called the South Atlantic Anomaly, I believe). So the ISS inhabitants are mostly shielded, although no where near as well as someone on the surface of the Earth, since the atmosphere also shields us.
Now the Chinese are thinking of going to Mars. Just what we need to get off the dime: a good, old-fashioned, Cold War-era space race! 
http://www.cnn.com/2006/TECH/space/07/19/china.space.reut/index.html
I’m surprised that no one has mentioned Voyage by Stephen Baxter, an account of a trip to Mars in an Apollo capsule in an alternate universe where Kennedy survived.
Pretty much all the events are analogous to things that happened in the Apollo program. I can’t testify to the feasibility of his mission profile, but I used to read a space science newsgroup, and lots of people there, who were qualified, thought he did a pretty good job.
In Titan he has a space shuttle going to Titan - but that is a lot more far fetched.
Triskadecamus is the closest to addressing the two main issues - and they are - available money and how it relates to our current methods of propulsion.
We can’t afford a Mars mission, with our current technology, so we really haven’t yet developed the technology needed for a Mars mission.
Let me explain in detail. 3 decades ago today, we sent a command module, complete with LEM, to the moon and back. Although our rocket engines may be
more powerful now and more efficient, than those used on the Saturn V rockets, Mars is 1000 times farther from the earth than the Moon. This means that to
go to Mars at the same speed would take 1000 times longer. So with our current methods of propulsion, it would take almost ten years - one way. Way too long for a manned mission to mars. But we do have a savior in this case. The earth is traveling around the sun at approximately 20 times the speed at which we first
journeyed to the moon. If we use Earth’s velocity to slingshot our spacecraft, a one-way trip would take only six months to a year.
So, what’s the problem? The law of physics called the Conservation of Motion. Because of the length of our voyage to Mars, we are going to have to utilize a much heavier spacecraft. While the increase in speed mentioned above, doesn’t seem like much, when we can slingshot our craft towards Mars, the weight of the spacecraft means that the small increase comes at very high cost. The speed at which a rocket is propelled forward depends on three things: the speed at which the propellant leaves the rocket, the mass of the expelled propellant, and the combined mass of the rocket and the remaining fuel. So… if we want our rocket to move faster, we have to expel more propellant out the back: but if we have to expel more propellant, we must start out with more propellant. But if we start out with more propellant, we must expel a little more the we would have to get the spacecraft (plus propellant) moving in the first place. But that means we have to bring along more propellant, which means we need a bigger ship, which
means… you see where this is going.
As our final velocity begins to exceed the speed of the propellant that is expelled, things change quickly. Increasing the velocity of our spacecraft form 1 to 2 times the speed of the propellant shooting out the back, requires 4 times as much fuel. Increasing final velocity to 4 times that with which our propellant leaves the spacecraft requires us to increase the required amount of propellant by a factor of more than 30. In this particular example, the initial mass of the ship plus propellant would be about 55 times the mass of the ship without fuel.
Now we must consider, that since a ship designed to carry such a large amount of propellant will have to be sturdier than it would otherwise have to be, it will weigh more than the type of spacecraft designed for the Apollo missions, or our current shuttle program. So this in turn limits our final velocity. With our current methods of propulsion, it is generally impossible to move a spacecraft faster than 3 or 4 times the velocity of the propellant. Remember, since this round trip to Mars may take a year or more, during which we have to adequately feed and house our astronauts, our spacecraft will weigh substantially more than an Apollo capsule. Since the total amount of propellant is a fixed multiple of the spacecraft weight, our net fuel requirement will be many times that associated with a trip to the moon, even if faster speeds were not required.
And, it just keeps getting worse… there is this matter of getting back. Mars has a stronger gravitational field than the moon. To achieve a trajectory back to Earth you have to carry a comparable amount of propellant for the return trip. This means the ratio of propellant needed for trip back, relative to mass of the now lighter spacecraft, is almost what would be needed for the initial journey to Mars. But, then this fuel must be added to the initial mass of the spacecraft, before we can calculate the initial propellant requirements. This becomes our main problem.
So, basically the Conservation of Motion laws, and our voyage duration limitations, dictate that the propellant required to achieve a sufficient velocity for a trip to Mars is 5 times the mass of the spacecraft with an empty storage tank. If you need a comparable ration for the return trip, then you would need to land on Mars with a spacecraft that weighed 6 times the mass of an empty spacecraft - that is, the mass of the empty spacecraft plus 5 times the mass of the spacecraft in fuel required for the return trip. Here’s the rub. This would mean that the mass our spacecraft plus propellant at the time of takeoff from Earth would have to be 36 times the mass of the empty spacecraft. We basically end up with a Star Wars battle cruiser.
The above scenario more or less covers why NASA first officially considered a manned mission to Mars in '89, and then just as quickly, decided against it.
The price tag back then was $450 billion - just for the spacecraft. Mars in our life time is a pipe dream. Show’s how little research the Bush administration did,
before once again bringing up the prospect of going to Mars.
The question was if money was NOT an issue, could off-the-shelf or similar components be used to construct a viable manned Mars mission. For the answer, see the above posts.
Mars Direct might be closest to what you’re thinking of, though Zubrin does seem to gloss over the radiation issue. Get the book The Case for Mars from the library and have a read.
Sorry. Scientits, engineers, and accountants (and everyone else) tend to deal with the everyday reality of budgets . Although I don’t agree with it, budgets will always be a stark reality during our lifetimes - when it comes to space travel (and evrything else).
:dubious:
Depending on the positions of the planets, it takes a probe from seven to 11 MONTHS to get to Mars, with our “current methods of propulsion”. Your ten years figure doesn’t make any sense at all.
He’s taking the Apollo spacecraft velocity and dividing the Mars/Earth distance by it.
According to this site, a Saturn V could deliver 63,000 pounds to Mars in .7087 years using a Hohmann transfer orbit. Granted, that’s a lot less than any manned craft would weigh, but it could have still delivered a payolad to Mars in a lot less than ten years.
Right but the command module et. al. traveled at 1.5 km/s. Pushing to Mars orbit you add on the relative velocity of the earth/moon system (~30 km/s), which reduces the time to 150 days.
We most certainly can afford it. We have just chosen to spend that money in other ways.
And the only reason a Mars mission would use any more fuel than a Moon mission is the fact that you’d probably want a larger payload (more life support, more living space to keep the astronauts from going insane, etc.). The distance itself is irrelevant.
Radiation vaccines are in the works.
Current estimates for the cost of a manned mission to Mars are $200 billion, the current tab for the war in Iraq is about $300 billion and expenditures for it are running at $3 billion a week.
I have seen proposals for making the mission to Mars a one way trip for the astronauts, which would probably be difficult to staff (though I’d be willing to go), but would save the hassles of transporting fuel for the return trip (though the fuel could be made on Mars).
It’s not a four letter word to me. I’m all for an Orion style launch program, get really large amounts of useful mass into orbit AND use up alot of dangerous weapons in the process. Just the thing we need to put what we need up there for a space elevator.