Why can’t we go faster in space?

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Okay, I’m an idiot. Just to preface this. But let’s say I’m in space. There’s no wind resistance right? If I accelerate, I’ll maintain that speed. Why can’t I just burn more fuel and go faster?

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13 Answers

Anonymous 0 Comments

Assuming unlimited fuel, we can still only go so fast based on the engine design and the speed at which the exhaust leaves the rocket engine. The exhaust coming out of the rocket can only go so fast. At some point, the mass of the rocket and the thrust of the engine are going to balance each other out.

To use an example, imagine we are talking about a hose.

If the water is coming out at a slow speed, the hose doesn’t zip around the yard, it just sits there. But if you turn up the water pressure, suddenly the water leaving the hose can push the hose around. That is basically thrust. The amount of thrust is based on the water leaving the hose. The water leaving the hose cannot push the hose backwards faster than the water itself is leaving. To increase the speed of the hose, we have to increase the speed at which the water leaves the hose. If the water leaving the hose is traveling at 10 mph, the hose cannot move faster than that. If we get it up to 20 mph, now the hose can start to whip around.

To use some real world examples, a shuttle engine exhaust is about 4500 m/s. the boosters were 2500 m/s. That is solid rockets vs liquid fuel.

Anonymous 0 Comments

Going fast is easy. Burn fuel, exhaust one way, acceleration the other way.

But going even faster is harder. The faster you go, the harder it is to go even faster, since it takes more energy to go faster than fast.

Eventually, you will reach a point at which you cannot go faster because going any faster would take more energy than you can have, so you eventually stabilize at some high speed.

It takes 4 times as much energy to go 2 times as fast.

Eventually, you will simply run out of energy to go faster – let alone going any faster relative to your current speed to notice any change in speed.

Anonymous 0 Comments

The Tsiolkovsky rocket equation.

You can go faster by burning more fuel, but you have to bring more fuel to accelerate the fuel you are going to use to go faster.

Beyond a certain point going a little bit faster means you need to carry exponentially more fuel.

Anonymous 0 Comments

When you accelerate in space you decelerate in time. So asking how you can go faster than the speed of light is like asking which direction you can point a meter stick to make it longer than a meter.

Now here’s the real kicker. As you transfer from time velocity to spatial velocity, the energy required increases exponentially. Eventually you reach a point where it requires more energy than the entire universe to accelerate.

Anonymous 0 Comments

Anyone that asks this question should play Kerbal Space Program. If you manage to land on the mun (the programs equivalent of the moon) you’ve answered this question and about 20 other questions you might have about orbital mechanics and accelerating through space.

The short answer is that since there is nothing to brace yourself against, every meter of speed you accelerate is basically your ship going that way because it’s shooting reaction mass out the other direction. The faster and more efficiently you can shoot mass out your rocket the faster you can go before running out of fuel.

Which is basically why an Apollo rocket is the closest humanity has gotten to “not quite a slowly exploding nuclear bomb” (because the fuel used is EXTREMELY explosive). Scientists even talked about using nuclear bombs to go fast into space (Orion Project).

Anonymous 0 Comments

If you really want to learn about rocket science, Kerbal Space Program is a great way to do it. It’s a game, but you will learn the basics and they will answer your question and a good bit more.

Anonymous 0 Comments

Motion of such large vessels is… difficult… logistically speaking in space.

Lets say, you’re in orbit over Earth, completely writing off the effort already undergone to get there in the first place, and you want to fly to Uranus as you’ve heard it’s particularly phat this time of year.

Well, you get there by burning fuel. Your thrusters overcome the weight of your vessel + the gravity well of Earth and your orbit expands ever outwards until you break free of Earths gravity and you’re sling-shot toward your destination… But, wait. Fuel is a heavy as shit. More fuel means more weight. So Earths gravity is stronger than ever, pulling on your heavy ass fuel tank. So now you need more fuel to overcome the weight of your fuel. *ah…*

That is the major problem. Mass in space is more fundamental than it probably first appears. Anything heavy needs a proportionate amount of energy to propel it. You need to precisely ration fuel, as you’re fighting against the various gravity wells you encounter on your journey, so the weight of said fuel needs to be the perfect ratio for the distance it will actually get you. You need to know when to burn to speed up, and to slow down to take advantage of gravity slingshots. It’s complicated stuff, and not just a “bee-line” to your destination.

So let’s say you figure that out. And you see Uranus on the… erm… “horizon”, and it is indeed as phat as they said. Say you wanted to orbit it. Well, uh oh… How do you do that? As you said, there is no wind resistance, no friction.

Your thrusters have gotten you up to the speed of a few thousand, maybe tens of thousands of meters per second. And it’s gotten you to Uranus… But what now? There are no brakes in space. To slow down, The only option is to burn the opposite direction to cancel out your momentum, which (you guessed it) requires more fuel. Which again increases your mass.

So in short, you need to make sure you have just enough fuel to get you to where you’re going, enough fuel to slow down enough to get captured in the gravity well of Uranus to circularize your orbit. And presumably enough fuel to escape orbit, and return home. Assuming no mistakes of course.

Anonymous 0 Comments

we do go faster in space then we used to.

Apollo 11 moved at a snails pace typing out at a 2.7 kilometer per second, voyager 2 is currently on cruise control at 12.4 kmps, New horizons,the Pluto mission hit 16.26 kmps that’s 16,260 meters in a second..

Anonymous 0 Comments

To add,

Regarding the whole rocket fuel thing, that’s called the [Tyranny of the Rocket Equation](https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation). The equation mostly describes the situation of overcoming gravity and lifting a payload off the ground. There are limits to how heavy a rocket can be given our material science today. As a thought experiment, if there were a rocky planet containing life elsewhere, with a civilization of comparable technology to us – if the planet were a bit bigger than Earth, then they could not build a rocket capable of escaping their planet’s gravity. They’d have to invent something more energetic, something stronger and lighter than what we can do today.

Once you’re in space, things are different. We could build a space ship in orbit of any size and load it up with all sorts of fuel and whatever. Technically, we could mine asteroids and other small bodies and potentially make the materials out there rather than down here. You’d have to play a game of time and orbital mechanics, perhaps several lifetimes to get the work done, but hey. It’s not necessarily practical or efficient.

But it would be nifty to accelerate like crazy. Not necessarily press you into the seat crazy, but, constantly crazy. A [1g](https://en.wikipedia.org/wiki/Space_travel_using_constant_acceleration) rocket would accelerate at a constant rate that would put it’s payload under 1g of force. It’s a dandy way to simulate gravity! But it’s also fast. You’re not just getting to your destination, but you’re getting there faster and faster. All you have to do is half way through the trip, turn the ship around, and accelerate in the opposite direction – so you don’t overshoot where you’re trying to go. This could cut down trips across the solar system to just a few days to get as far out as Pluto. A trip across the galaxy would take 12 years – I’m quoting a figure, I don’t know if they factored in slowing down.

Anonymous 0 Comments

You can, what you are looking for is specific impulse, ion engines are the ones with the highest impulse and over long periods of time they can get to massive speeds, but that is relative to earth.

When going somewhere in space you have to think not only where is your target but how its moving.

Also how are you going to brake. I f you wanted to go to the moon the fastest way possible you dont only have to think about how you accelerate but how you brake. Braking in space is more limiting than accelerating.