Nuclear Interstellar Probe?

Why couldnt we use a nuclear engine on a probe and send it to an interstellar earth like planet? I think if it had about 100,000 mph acceleration it would reach light speed in about a year or so. And would get faster and faster as long as it had fuel. Is that possible?
Maybe send all necesary supplies and instructions for return trip so the aliens can send a message back.

Originally posted by earth2
Why couldnt we use a nuclear engine on a probe and send it to an interstellar earth like planet? I think if it had about 100,000 mph acceleration it would reach light speed in about a year or so. And would get faster and faster as long as it had fuel. Is that possible?
Maybe send all necesary supplies and instructions for return trip so the aliens can send a message back.

you have a fascinating idea. the raw energy of nuclear power does sound capable of doing as you suggest, but do we have the propulsion devices neccesary to fulfill such a thought? in other words, we may have the gas for the engine but we don't have the engine to run on the gas.

Something like this?
Or am I way off on your idea?

E=mc² is the limiter with your idea of a nuclear rocket, or any other fuel source that we now have knowledge of...As a craft approaches the speed of light, its mass and thus the amount of fuel it would take to increase its velocity, approaches infinity. Its like closing the distance between you and the other side of the street if you keep halving the distance with each step, the first step you take, you're half way there, then the next, 1/4 way to go...but as you halve the rest of the steps, it approaches infinity to reach the other side.

Originally posted by greatlakes
E=mc² is the limiter with your idea of a nuclear rocket, or any other fuel source that we now have knowledge of...As a craft approaches the speed of light, its mass and thus the amount of fuel it would take to increase its velocity, approaches infinity. Its like closing the distance between you and the other side of the street if you keep halving the distance with each step, the first step you take, you're half way there, then the next, 1/4 way to go...but as you halve the rest of the steps, it approaches infinity to reach the other side.

Calculus has something (limits i think?) that solves this problem. Although i can't remember exactly because i took calc over 4 years ago. People realized that if you keep halving, you must eventually reach the other side of that street, so this function was invented. Maybe a math wiz here can identify the name for this.

Here is a cool article regarding a possible fuel for interstellar travel.
It looks like antimatter is the ticket.

archives.cnn.com...

"The energy you get from the anti-particle particle annihilation is about ten billion times that of chemical combustion,"

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changed quote tags with 'ex' tags

[edit on 7/7/07 by masqua]

Originally posted by earth2
I think if it had about 100,000 mph acceleration it would reach light speed in about a year or so. And would get faster and faster as long as it had fuel. Is that possible?

Just to be picky here 100,000mph is a velocity (speed) to describe acceleration to have to square it - 100,000 miles per hour per hour would be an acceleration.

The acceleration due to gravity on Earth (ie how fast you would accelerate if you fell out of a tree) is 9.8 meters per second per second (9.8 m/s/s), after 1 second your velocity would be 9.8 meters per second, after 2 seconds your velocity would be 19.6 meters per second - not accounting for friction etc.

As for light speed, the theroy of relitivity says no. Thats not to say its right, but you'll have to be very certain of your self to argue with it.

According to Einstein there is not enough energy in the entire universe to propel a craft beyond the speed of light. Its a bit like that puzzle where you tell someone to put one grain of rice on the first square of a chess bord, two on the second and continue doubling for every square. How much rice will you have on the last square?

9,223,372,037,000,000,000!

or: 230,584,200,900 tonnes (based on 25g / 1000 grains)

That is equivilent to one hundred billion, two hundred and fifty four million fourty three thousand nine hundred elephants (based on 2300kg / elephant) *phew*

In short, the faster you go, the more energy it takes to double your speed, the closer you get to light speed (using current thinking) the more power you will need.

nowthen, I have a hard time figuring all that out but the way I think is if you are coasting through space at 100,000 mph and then turn on the rockets again wouldnt you start accelerating again as if you were standing still since space is a vacuum? Wouldnt you gain speed increasingly as long as you had fuel?
I dont understand the einstein theory in that area because using common sense it seems there would be no end to your speed as long as there is fuel.

Originally posted by Now_Then

Originally posted by earth2
I think if it had about 100,000 mph acceleration it would reach light speed in about a year or so. And would get faster and faster as long as it had fuel. Is that possible?

According to Einstein there is not enough energy in the entire universe to propel a craft beyond the speed of light.

Actually, there is not enough "Matter" in the universe to be used as chemical propellant. And, we aren't just talking about attaining the speed of light. But, yes, there is not enough matter in the universe to attain the speed of light through chemical propellant means. That is the problem dealing with "Velocity".

The other problem is "Distance + Time". To make a trip of just 4 or 5 light years, in, say, under 1,000 years, there is not enough matter in the universe, to be used as propellant. And that trip would be at a fraction of light speed.

The fact that we are aware of these other celestial bodies floating out there in space, and how we can actually observe their light and effects on the rest of the universe, has inadvertently created a false notion of "travel" for the layman.

Light is a trickster.

The distances we are dealing with are unbelievably VAST!

I can't track down the exact location of the article where I found the following information. So, if any of you have come across it, let me know so we can give them credit.
Here are some pretty crazy fuel projections for a trip to Alpha Centauri, 4 light years away:

Let us say you have an object about the size of a space shuttle and you want to send it to Alpha Centauri at a rate of speed that it will arrive there in 900 years.

nuclear fission? Well, that might work, but you would need a fuel tank the size of one billion supertankers.

fusion, it provides more energy, right? Yes, it does, but you would still need a thousand supertanker sized fuel tanks to transport you there on time.

Ion engines? Those, too, would work, but you would still need ten railroad cars worth of fuel to get there.

To send a shuttle sized object on a 50 year, one-way trip to Alpha Centauri, it would take more than 7 x 1019 Joules of energy. This is approximately the same amount as if the space shuttle engines were to be run constantly for 50 years.

The main problem with current propulsion is the enormous amounts of energy needed to attain such high speeds, especially for long periods of travel time. If you were to convert energy directly into motion, it would still take tremendous amounts of energy to create the motion necessary for interstellar travel.

Originally posted by earth2
nowthen, I have a hard time figuring all that out but the way I think is if you are coasting through space at 100,000 mph and then turn on the rockets again wouldnt you start accelerating again as if you were standing still since space is a vacuum? Wouldnt you gain speed increasingly as long as you had fuel?
I dont understand the einstein theory in that area because using common sense it seems there would be no end to your speed as long as there is fuel.

You're confusing speed with acceleration.
You're correct in assuming that a spacecraft coasting at 100,000mph that lights off its engines (be they nuclear, chemical, or dilithium) will begin to accelerate (assuming that fuel is available). The question then becomes 'how fast does it accelerate?'. How long did it take your vehicle to get from at rest to 100,000 mph? That's about how long it will take to get from 100,000 to 200,000 mph. You just doubled the amount of fuel you needed, as well (thanks to that second round of acceleration). Of course, you have to accelerate the additional fuel up to 100,000 mph, so you now need more thrust...which requires bigger engines...which requires more fuel. Now, imagine repeating that sequence until you reach 670,615,200 mph....the speed of light. Even without relativistic mass sticking its ugly face into the discussion, the fuel load would be a killer.

Even if (by some miracle) you could reach light speed, the trip to the nearest star would take most of five years....one way.

Given our current (or even our foreseeable future) technology, interstellar travel is going to be a multi-generation affair, I'm afraid