Say we land on mars. And take a walk around. How are we supposed to get off? What are NASAs ideas to launch a rocket off mars? wouldnt we need a whole big rocket with a scaffold?
Remeber the moon landings, to get off the Moon much less powerful rockets were required than to get off Earth. Mars’ gravity is greater than the Moon’s, so getting off Mars is a big consideration for NASA, but it’s still quite a bit less than the Earth’s.
Dr. Bob Zubrin has proposed a ship that would carry its own supply of hydrogen, and then use basic chemistry to mix the hydrogen with Mars’ atmospheric gases (mostly CO[sub]2[/sub]) into CH[sub]4[/sub] (methane) and O[sub]2[/sub] (oxygen gas). This gets you a rocket propellant combination with a specific impulse in the mid-300s, which isn’t bad. As a bonus, you can use the hydrogen several times if you’re careful, producing H[sub]2[/sub]O and O[sub]2[/sub] for use by the crew. You just need to be aggressively careful about reusing and recycling your waste products.
The plan is spelled out in detail in his book The Case For Mars if you’re interested in more details.
Escape velocity
Earth 11.186 km/sec
Mars 5.027 km/sec
Moon 2.38 km/sec
Find a couple (or more) Martian ladies. That should do it!
d&r
Keep in mind that when launching from Earth, the atmosphere is a huge obstacle when trying to get to orbit. If you try to get up to orbital speed quickly, you have to use a lot of fuel pushing your spacecraft through the dense atmosphere at high speed. Think of the enormous amount of fuel used by supersonic jets to maintain a measly Mach 2 or so; then recall that orbital speed of 7 km/s translates to about Mach 24. Or you could try to move through the atmosphere slowly, but then you spend a lot of time - and therefore a lot of fuel - fighting against gravity.
The atmosphere of Mars is about 1/100 as dense as the Earth’s. The rocket needed to launch from Mars to orbit is much smaller than what you’d need on earth.
And of course, the rocket will likely carry a tiny capsule containing only the crew and scientific samples. It can then dock with the spacecraft waiting in orbit. Just like the Apollo missions.
It’s an obstacle, but I don’t believe a huge one - at a guess, it adds 5% to the energy needed to achieve orbit. Various Googling is inconclusive, but seems to indicate that the Shuttle is above 99% of the atmosphere at around 90 seconds after launch.
If you tried to do orbital-type speeds near the earth, fuel consumption would be only one of your big problems.
Dude, haven’t you heard?
Why don’t we ‘just’ build a space elevator on Mars - after all, everyone seems to be agreed it would be a doddle here on Earth - where some of the engineering challenges and design criteria are actually much more severe than they would be on Mars.
Well then, how about an extremely flexible pneumatic tube tethering the two planets?
If only we could get that pesky “sun” out of the middle …
Which says nothing, unless you also have a figure for how much of the Shuttle’s fuel it’s burned at T+90.
The ideal solution would be to build one on Earth first, and use the one on Earth to build and launch another one to Mars. A single functional space elevator makes everything regarding space much easier, including building more space elevators.
Yes, but apparently it got them!
Great. All this money on rovers and stuff, and the Dutch beat us to Mars.
That would be the Danes, no? In the Netherlands we have absolutely nothing to do with mermaids in harbours, I swear!
(unless you sample certain somethings from the coffee shops; then you may end up seeing anything at the harbour. Or in a Mars rover photo).
Just my 2 eurocent!
JoseB
F&ck-a-doodle-doo.
Yes, you’re correct.
Goddamn Danes always tricking me with their confounded not-being-Dutch-ness.
This page describes the dynamic force on the Shuttle as it ascends to orbit. It only has the dynamic pressure listed and I don’t know the exact frontal area and Cd of the Shuttle, but assuming 2000 ft[sup]2[/sup], the force at max-Q is roughly 1.5 million pounds. That means something like 1/4 of the thrust is used to fight air resistance. (These are very rough guesstimates; please post if anyone has better numbers.)
Booooo!
The rocket to lift off the surface of Mars will indeed be smaller than what’s needed to get off the Earth; but I was wondering how come rockets on Earth need the nursemaiding of a multi-billion dollar launch complex, while the Mars ascent stage will be taking off from the middle of a desert on it’s own.