How is the fuel used on a trip to mars ?

Question

Is it mostly on acceleration to speed and then back to zero?
Also why is the speed of choice always seem to be around 25,000 MPH

Answer 1

u can probably find that out, but i think it has to do w/ ppls wieght also they gotta have enough fuel to go there and bring all that weight back w/ them.

Answer 2

Mostly acceleration up to speed in the first 10 minutes after launch. And 25,000 MPH is the minimum speed you need to leave Earth at so that you can shut down the rocket engine and never be pulled back to Earth. It is called escape velocity. They don't go much faster because they can't carry enough fuel.

Answer 3

The escape velocity from Earth is about 25,000 MPH. Slower than that, and you'll have a VERY high orbit, but it will still be an orbit. Anything above that speed will eject you out of Earth's orbit.

Generally, most spacecraft boost their speed as quickly as possible, and exhaust their fuel, leaving them to coast most the way to their destination. Speed and course is calculated as precisely as possible, so that an orbiting craft (around Mars, say) will arrive at Mars with just about the right amount of speed to 'fall' into orbit.

If you can carry a good amount of fuel, you don't have to be so careful about speed, but it's a trade off... The weight of fuel prevents you from carrying more science equipment with you.

When Cassini went to Saturn, it had a long burn to place it into the desired orbit about Saturn - if the engine didn't burn for the full time, it would've skipped by the planet altogether.

When we sent astronauts to the moon, we placed them on a "free return" trajectory - They left Earth's orbit at a certain speed & direction, such that if the engine failed at the moon to place them into lunar orbit, they'd swing around and come back to Earth.

Answer 4

The speed of choice is 25,000mph because that is the speed needed to escape Earth's gravity, or at least to resist it enough to be caught by the gravity of something else. Travelling at less than 25,000mph the ship would never get to Mars. It would slowly loop round and come back to Earth.

On a trip to Mars the fuel will be used accelerating the ship away from Earth. Once the speed reaches or exceeds 25,000mph the engines will only be needed for course corrections on the way out. Most of the time will be spent coasting. Course corrections will be short burns of probably smaller engines, just to nudge the ship onto the precise trajectory needed. Once at Mars there may be some fuel used for braking in order to slow the ship sufficiently to be captured my the gravity if Mars rather than simply swung round it and catapulted away somewhere else. There may also, to save on fuel, be some aerobraking involved, skimming the craft off the atmosphere of mars in order to slow it down (Mars has a very thin atmosphere, but at re-entry speeds even that is enough to produce huge amounts of friction and heat).

Contrary to popular sci-fi shows, most of a journey through space is coasting. With no air to produce drag you'll get where you want to go just by pushing yourself to a high enough speed and turning your engines off.

Answer 5

#1
Assumption 1: Start from Earth orbit
Assumption 2: No Mars landing
Assumption 3: Propulsion fuel only; Exclude vehicle attitude and environment control fuel

Fuel required
A: To transfer out of Earth orbit onto interplanetary trajectory towards Mars must attain escape speed from Earth's gravity plus speed to Mars; more fuel + shorter trip & less fuel longer trip.
B: Mid course correction to insure Mars orbit insertion
C: Repeat A & B to return

#2 Must attain escape speed

Answer 6

Since there is almost no friction in space, there is no need to burn extra fuel overcoming it. With the exception of minor heading adjustments, almost all of the fuel would be used in liftoff and landing.

Answer 7

hedlogen