« on: November 05, 2007, 03:22:09 PM »
December 98, Sec 2, 9
The only physical factor preventing a human journey to mars has been weight. Carrying enough fuel to propel a conventional spacecraft to mars and back would make even the lightest craft too heavy to be launched from Earth. A device has recently been invented, however, that allows an otherwise conventional spacecraft to refill the craft's fuel tanks with fuel manufactured from the Martian atmosphere for the return trip. Therefore, it is possible for people to go to Mars in a spacecraft that carries this device and then return.
Which one of the following is an assumption on which the argument depends?
TCR: THe device for manufacturing fuel for the return to Earth weighs less than teh tanks of fuel that a conventional spacecraft would otherwise need to carry from Earth for the return trip.
Unfortunately, this was answer E and I was quick to bubble in an earlier answer before getting to this. Why is this one wrong, however?
The amount of fuel needed for a spacecraft to return from Mars is the same as the amount of fuel needed to travel from Earth to Mars.
What if you needed 10,000 times the amount of fuel to return from Mars to Earth? Then that manufactured fuel wouldn't necessarily fit inside the fuel tank if it was made to fit only for the trip from Earth to Mars, right? I'm confused. Help?