Can we get men to mars?

Do we currently have the technology to land men on Mars?

I wanted to open this up on the great debates thread, because we have
been discussing this at great length in the General Discussions thread, and
there are vastly differnt opinions being stated.

My answer is emphatically, NO. 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 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 ratio 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. Most of the above was explained in detail in a great book by Lawrence M. Krauss. I plagerize his work often - but only on discussion threads.

The above scenario more or less covers why NASA first considered a manned mission to Mars in '89, and then quickly decided against it. The price tag back then was $450 billion!! 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.

I don’t want to get too deep into this but we get probes to Mars much quicker than 10 years. If you do some rudimentary research (Buzz Aldrin’s book is a good start), I think you’ll find it’s feasible to get people there in 5 months.

Try googling Buzz Aldrin Mars mission and read the Popular Mechanics article.

Try reading my post again. “If we use Earth’s velocity to slingshot our spacecraft, a one-way trip would take only six months to a year.”

I’m confused, mr_wired; you mention slingshots briefly, then go on to dismiss methods that use raw propulsion; what was the problem with slingshots again?

Also, you appear to have assumed that everything needed for the return journey needs to be packed in a single outbound craft. Why should it? Why not send a bunch of unmanned craft containing big fuel reserves (perhaps also supplying materials and equipment for the Martian sojourn); send them there first, using a trajectory that is cheap on fuel at the expense of journey time. When these are established in orbit around Mars, send the manned craft.

Certainly, though the radiation the folks on the ship would take is still a worry. Disreguarding that however, we certainly have the technology to put humans on Mars…and have for some time now.

Here is one plan I’ve seen before called Mars Direct (you can get more info on it if you google Mars Direct btw…this is just a thumbnail view):

There are, of course, many other plans. This one is quite risky (and would probably cost more than the $20 or $30-35 billion listed)…others are safer. And of course there are new, nuclear continuous thrust rocket engines that are on the horizon and should be ready for use by the time we actually get around to doing a trip to Mars…but you asked about off the shelf stuff.

What technology are you thinking we need? As long as we were willing to risk the safety of the crew wrt the radiation (you didn’t specify we had to SAFELY get the crew to Mars after all), I don’t see any show stoppers myself.

Um…huh? I have no idea what the hell you are getting at here. No plan I know of (using technology currently available) doesn’t use a slingshot trajectory to get to Mars. There are several viable flight paths…and all of them get the crew to Mars between 6-8 months after they leave. Its a long ass trip, no doubt…but what exactly are your objections?

No, I don’t exactly see where you are going to be honest. Your objection seems to stem from a fundamental misunderstanding of how physics and rotary motion works wrt interplanetary travel. Afaik (granted its been decades since I took those aero-space classes in college) there is no real show stopper wrt GETTING a craft large enough to hold a good sized crew to Mars in a timely fashion. The biggest show stoppers is crew safety due to the high levels of radiation they would take on the trip (though there is a lot of research going on in methods to either shield the crew or perhaps use medical methods to alleviate the effects of the radiation).

Um…I ask this tentatively, but, do you actually understand how a slingshot trajectory works in planetary travel? Because it doesn’t seem to me that you actually do. Once the leaves Earth orbit on a specific vector it doesn’t NEED to do more than perhaps a few course corrections…gravity takes care of the rest. Are you saying that you don’t believe that we can make a craft that can break Earth orbit??

On the off chance you don’t understand gravitational slingshots, here is an article from the ever useful Wiki :

Well, thats certainly a valid objection…the price tag. And if you want to put it in those terms, then you have a valid point. If the price tag to go to Mars is too high, then we won’t go. It won’t be for technical or physics reasons though, which seemed to be the direction of the majority of your OP…but simply because we can’t afford it.

Realize though that that price tag of $450 Billion was completely bloated and had stuff like a space station (to act as some kind of funky transfer point)…even NASA conceeds this. The actual price of going to Mars would be significantly less than that…depending on the level of risk that would be acceptable. I’ve seen ball park price ranges from $80 billion to $200 billion…my guess is it would fall somewhere in that range. About the price of our Iraqi adventure…




Affording it is a different issue entirely.


What?? Return trip? You want to know what our problem is today? We’re out of Chuck Yeagers. Sometimes you have to just damn the torpedoes and go full speed ahead. Innovation and discovery go hand-in-hand with risk. Do you think NASA of Geminii and Apollo days had all the answers worked out before sending men into space? No. They worked some of it out as obstacles presented themselves. Sometimes they were met with disaster, but there was no shortage of adventurous souls out there willing to literally put their lives on the line for glory.

We can get men to Mars …and we can figure out how to get them back. Necessity is truly the mother of invention.

I don’t mean to discount your physics dissertation, but if all we do is look at the math and resign ourselves to perceived insurmountabilities we’ll never get anywhere.

According to a Discovery magazine I was leafing through in a store recently, a more serious problem may be that of cosmic rays. It’s not definitely established that we can even live outside the Van Allen belts for the time it would take to reach Mars.

To think we can’t even get to Mars, and yet we’re only 11 years away from the fictional discovery of Warp Drive in the Star Trek canon. A bit depressing, that, if you grew up in the go-go era of space travel in the 1960s.

Yeah, but two years after that, the Replicants’ll kill everybody.

You mean that in 11 years, we will discover a fictional warp drive? Oh, I get it, warp drive was discovered in 2017 in the fictional Star Trek universe. Your post confused me for about 15 minutes, I need more coffee.

As far as going to Mars, just north of Pittsburgh on the 228 I believe.

It came up in this GQ thread that radiation in interplanetary space might be a much, much bigger problem than previously believed. The Apollo astronauts had no problem with it on short-duration trip, but a Mars mission crew would be traveling through space at least a year (6 months there, 6 months back). They would require very heavy shielding and that would change all the calculations and parameters.

Ahhh, they’re 2010’s style “Warp Drives”.

No, we’ve got plenty of them. If NASA honchos were to approach astronauts, scientists, and military pilots and say “We want to send a man to Mars. But there’s a better than even chance that he’d die horribly. Any volunteers?” They’d have no trouble getting them. They’d have to set up a complex program to weed out the less qualified candidates.

The problem is that we as a society have decided that pushing forward the frontiers of science and technology isn’t worth the life of Chuck Yeager, even if he’s ready and willing. During the space race we had something to prove. We had to beat the Commies to the moon, or they’d paint a hammer and sickle on it. Now? It’s just science. Not even science immediately and directly applicable to everyday life. Yeah, we’d like to see an American flag on Mars, but if someone died putting it there, we’d feel awfully bad about it.

The more I read about it, the less likely it seems that we can get people to Mars and back with current technology. We might be able to get someone there, but they probably would be exposed to eventually-fatal levels of radiation en-route, and I don’t see how we could get them back. It might still be worth it to get some volunteers for a one-way trip to Mars and get some useful information out of the expedition before the volunteers expire.

The most probable way of working around this issue is to create or modify humans beings with immunity to radiation, kind of like this.

You are right…the problem is, we can get SO much from robotic exploration, and spend so much less, that a manned mission just isn’t worth it. Now, if we had heavy-lift Nuclear rockets, we could get there and back in much less time. But I am not convinced it is worth it. the next generation of martain Rovers will be fully autonomous , and will be able to gather tons of information. And they don’t have to eat, drink, and breath.

Now that is a ‘real’ “Scientific Journal,” NOT.
I’ve been reading PM and PS off and on 75 years and they have more BS than ever comes to fruitation.
It’s pie in the sky stuff from cover to cover.
Whatever eventually comes to market or realization is barely recogonizable as the published article.
OK. So I’m a little skeptical. :wink: