i don't follow. if we've mastered getting stuff off earth, which has higher gravity that mars, what's the problem with getting stuff off mars?

The largest issue with putting humans on mars, then bringing them back, is not the travel between Earth and Mars. It is getting the people back off of Mars back into space.

The moon has 16% the gravity of Earth (2.4km/sec escape velocity) and virtually no atmosphere, so it took relatively little thrust to lift the lander module back into orbit.

Mars has 38% earth's gravity (5km/sec escape velocity), and it does have an atmosphere (even if minuscule when compared to Earth).

Unless we can figure out how to land, fuel, and launch a pretty significant rocket ship from Mars, then anyone that goes is going to have a heck-a time getting back off of Mars.

Ok let me simplify this concept for you. Earth. Small ship from Earth rendezvous with big ship in orbit.

And how did you get the big ship into orbit? :)

Our biggest problem isn't getting stuff from planet to planet - if all else fails, we can always strap some nukes on our backs.

Our biggest problem is getting stuff from planets to orbit. 22% extra thrust doesn't sound much, but that's 22% we need to store somewhere, 22% extra fuel in addition to the biggest rocket ever built that has to be not just landed on Mars safely, but also brought from Earth to orbit in the first place - each and every time you want to go there. Last time we did it, we did a couple of trips and then stopped, because it simply wasn't worth the money. If we do this again, we'd be doing it for prestige and a couple of rocks at best - if we're in it for the long haul, we desperately need a system that will efficiently bring stuff into orbit. Solve that and the space colonization may well be on its way.

You send it up first and dock it with the ISS. How hard is this to understand?

The ISS is definitely built for storing rocket fuel in significant quantities, mhm.

I saw one article where it was proposed that the Mars Ascent vehicle be fueled with CO2. It would be heated by an on-board nuclear reactor to power the rocket engine. The CO2 comes from the Martin atmosphere. The article said that it would only take a few hours to compress and liquify sufficient CO2 to fill the tanks of the Mars Ascent vehicle. The method is:

A turbo-compressor compresses the CO2.
Half the compressed gas is cooled to Mars ambient temperatures, sufficient to liquify the high pressure gas.
The other half is run through the reactor and heated.
Its then expanded through a turbine. The turbine power runs the compressor and is used to generate electricity to help run everything.

When its time to take off, liquid CO2 is taken from the storage tank, pumped through the reactor and expelled through a nozzle.

Now another point: They have yet to get a fusion reaction. Their compression method is inherently unstable. So far every time someone tries the method they describe it works fine at compressing gas at low power. The instabilities have not grown big enough to interfere. But as soon as they raise the power sufficiently to get fusion the instabilities grow, the plasma finds a way out, and the needed pressures and temperatures are not achieved.

We should just blow up mars so people can stop wasting money on this crap

i don't follow. if we've mastered getting stuff off earth, which has higher gravity that mars, what's the problem with getting stuff off mars?

can someone explain this part me? i need to work on my space nerd-fu.

NASA Guy wrote:
Several low-mass, magnetically-driven metal liners are inductively driven to converge radially and axially and form a thick blanket surrounding the target plasmoid and compress the plasmoid to fusion conditions. Virtually all of the radiant, neutron and particle energy from the plasma is absorbed by the encapsulating, metal blanket thereby isolating the spacecraft from the fusion process and eliminating the need for large radiator mass. This energy, in addition to the intense Ohmic heating at peak magnetic field compression, is adequate to vaporize and ionize the metal blanket.

The largest issue with putting humans on mars, then bringing them back, is not the travel between Earth and Mars. It is getting the people back off of Mars back into space.

The moon has 16% the gravity of Earth (2.4km/sec escape velocity) and virtually no atmosphere, so it took relatively little thrust to lift the lander module back into orbit.

Mars has 38% earth's gravity (5km/sec escape velocity), and it does have an atmosphere (even if minuscule when compared to Earth).

Unless we can figure out how to land, fuel, and launch a pretty significant rocket ship from Mars, then anyone that goes is going to have a heck-a time getting back off of Mars.

Getting people to Mars is more than just leaving Earth...you have to find a way to a) leave Earth, b) reach Mars, c) land on Mars, d) leave Mars, e) reach Earth, f) land on Earth. Each of those individually is a nightmare of planning, preping, coordinating, and exicuting to say the least.

The largest issue with putting humans on mars, then bringing them back, is not the travel between Earth and Mars. It is getting the people back off of Mars back into space.

The moon has 16% the gravity of Earth (2.4km/sec escape velocity) and virtually no atmosphere, so it took relatively little thrust to lift the lander module back into orbit.

Mars has 38% earth's gravity (5km/sec escape velocity), and it does have an atmosphere (even if minuscule when compared to Earth).

Unless we can figure out how to land, fuel, and launch a pretty significant rocket ship from Mars, then anyone that goes is going to have a heck-a time getting back off of Mars.

The really tricky part is the landing on mars in something big enough, and having enough fuel in it, to get you back into orbit.

Actually, most of that is pretty easy for us given out current technology. we have lots and lots of experience getting stuff off the earth and into orbit.

We have experience assembling things in space. A rocket to Mars would be like the international space station, with a motor and lots and lots of fuel.

Stopping when you get to mars is even pretty easy since you can air brake off it's thin atmosphere and do other tricks with elongated orbits.

Assuming you've brought enough fuel, getting back to earth is pie. And stopping once you get here? again, pie with the earth's atmosphere to orbit through.

The really tricky part is the landing on mars in something big enough, and having enough fuel in it, to get you back into orbit.

My dad is the rocket scientist, but as I recall the numbers, using a chemical rocket to accelerate 1 ton payload to earth escape velocity of 11km.sec, requires 5 tons of propellent. To lift that 5 tons of propellent out of the atmosphere, requires 20 tons of propellent. Add on the weight of the lifting body that hold the propellant, and you're talking 35-40 ton rocket to lift a 1 ton payload.

On Mars, with the lower escape velocity of 5km.sec, lifting that 1 ton payload would require 2.5 tons of propellant, and lifting that 2.5 tons of propellant would require only 6 tons of propellant. However..... landing that... 10 tons of space ship on Mars would require 25 tons of fuel to slow the ship from orbital velocity and overcome the acceleration due to gravity. So, you are back to something the size of the rocket needed to launch the 1 ton from earth.




Again, the moon, with 1/6th the gravity of the earth, an very low escape velocityi, would take less than a ton of fuel to accelerate a ton to orbit, and less than a ton to lift that propellant... then less than that to lower the ship to the moon in the first place.

People care about internettspaceships as much as they care about real space ships :D

Anunzi: That stuff is beyond cool :D

Jacob: Are you refering to the Orion project?

Jacob: Are you refering to the Orion project?