once maximum speed is reached in outer space (presumably by firing the rockets) does this mean the rockets/engines can be turned off and the spacecraft will continue at the same speed without power as there is no friction in space. Space being a vacuum? Also how fast do spacecraft go en route to the moon or mars?
2006-07-07 22:03:43 · 9 answers · asked by Anonymous in Science & Mathematics ➔ Astronomy & Space
Thank you: One additional query. It has been suggested in these answers that a rocket needs to escape the earth's atmospher/gravitational pull at 25,000 miles per hour. How long does it take to reach this speed and how do the astronauts withstand the accelaration?
2006-07-08 06:13:41 · update #1
Rocket engines can be switched off as soon as all gravitational forces and friction are absent. In practice, they are switched off as soon as a spacecraft is free of the atmosphere (and its friction) and has reached or exceeded escape velocity for the celestial body from which it is departing. There are other variables, though, so it's hard to give a general answer.
Apollo 10 reached a speed of 39,897 km/h (24,791 mph) on May 26, 1969. This is about 0.0036% of the speed of light.
2006-07-07 22:19:01 · answer #1 · answered by Techwing 7 · 3⤊ 1⤋
They continue to move due to the momentum established when the rockets were firing. It's a little like a boat. It doesn't stop when you turn the engine off. It keeps moving until it is physically stopped. Of course a boat has the drag of the water so it will stop after a short distance, unlike a spaceship which has nothing in space to cause any resistance. "If we imagine that the rocket is in outer space, far from the earth, then there are no drag forces or gravity so there are no external forces on the rocket or the gases it expels."
2016-03-26 21:20:46 · answer #2 · answered by Anonymous · 0⤊ 0⤋
Engines can be switched off only due to the vacuum in space.
But gravity is never zero. That another story.
Engines can remain switched off orbiting a planet or satellite. Then the rocket is 'in free fall' in an elliptic orbit around the planet. Now the gravity is used as necessary centripetal force.
When the rocket wants to escape this orbit, again it needs its engines.
2006-07-07 23:32:51 · answer #3 · answered by Thermo 6 · 0⤊ 0⤋
Yes. The rockets never fire for more than a few minutes, all the rest of any space mission is just coasting. To go to the Moon the rocket leaves Earth at 25,000 miles per hour. The speed does not stay the same, but it is gravity, not air, that slows the the rocket down to only about 3,000 miles per hour by the time it gets to the Moon. Think of it this way. If you throw a rock up, it leaves your hand going fast, but slows down as it gets higher until it stops, and then falls back to the ground. If you throw the rock faster, it goes higher. If you threw it up at 10,000 miles per hour, it would go thousands of miles high before slowing to a stop and falling. If you throw it at 25,000 miles per hour, it goes up and up, slowing down as it goes, but it never slows all the way to zero speed. It just keeps going higher and higher, and slower and slower, for ever. That is why they call the speed of 25,000 miles per hour escape velocity. It is the speed you need to escape Earth's gravity forever.
To go to Mars the speed is a little faster, but not much. Maybe something like 30,000 miles per hour. Again, gravity changes that during the flight. The extra few thousand miles per hour above 25,000 is needed to overcome part of the Sun's gravity.
In Earth orbit, the speed is 17,500 miles per hour, but since the rocket is not trying to go higher, gravity does not slow it down, it just coasts at 17,500 miles per hour while staying at the same altitude with no rocket engines firing, for days and days.
2006-07-08 03:50:42 · answer #4 · answered by campbelp2002 7 · 0⤊ 0⤋
complete Vacuums are rare.. even between planets, there are forces acting upon that space and space junks are littered. So rockets cannot possibly stay at that speed.
2006-07-07 22:29:53 · answer #5 · answered by J.M. 2 · 0⤊ 0⤋
Yes. Once an object starts mooving in space it will continue moving.
2006-07-08 04:17:22 · answer #6 · answered by Eric X 5 · 0⤊ 0⤋
Yes, as there is no friction it won't slow down but stay at the cruising speed.
2006-07-07 22:08:00 · answer #7 · answered by The Great Turtle Speaks 2 · 0⤊ 0⤋
It's not because it is a vacuum, it is because it is a frictionless void; but yes, the engines can be turned off and "coast" indefinitely.
2006-07-07 22:09:27 · answer #8 · answered by xtowgrunt 6 · 0⤊ 0⤋
Unless it's affected by gravity of another object.
2006-07-07 22:09:26 · answer #9 · answered by J_DOG 3 · 0⤊ 0⤋