Tell me what you think about this.

[Chris321]

So I’ve been playing this cool space travel game and Out of no where I had a couple ideas pop into my head on the game I was trying to find as many earth-like planets as I could and I found out that other scientists have been trying to find life on other planets as well so I thought maybe instead of searching the universes so aimlessly we could  narrow down our search for other earths by looking at universes that have suns with same temperatures color and sizes as our own sun. I had another Idea as well  constructing a rocket engine that’s capable of releasing all of the rockets fuel at once I thought this could maybe make rockets travel faster than normal what are your thoughts on this ? I’d love to hear opinions.

[Bufofrog]

Welcome.

I think you mean solar systems not universes.  We have found "earth like" planets orbiting stars that are not like our sun.  A rocket that fired all its fuel at once is essentially a cannon.  The g-forces would kill the Astronauts.

I am glad you are thinking about these things.  The thing about science is the more you learn the more fun it is.

Edited May 15, 2019 by Bufofrog

[Strange]

7 hours ago, Chris321 said:

I found out that other scientists have been trying to find life on other planets as well so I thought maybe instead of searching the universes so aimlessly we could  narrow down our search for other earths by looking at universes that have suns with same temperatures color and sizes as our own sun

Stars like our sun are relatively rare. Also, it would limit the search for planets that could have life far too much; Earth-like planets can exist around different types of stars. Also, planets capable of supporting life (even if they are not Earth like) could exist in an even wider range of conditions.

7 hours ago, Chris321 said:

I had another Idea as well  constructing a rocket engine that’s capable of releasing all of the rockets fuel at once I thought this could maybe make rockets travel faster than normal what are your thoughts on this ?

Controlled acceleration is much more efficient than a single explosion. Also, spacecraft need to control where they are going. That requires fuel and so would be impossible f was all used up in one explosion.

[Janus]

When dealing with rockets, its the speed of the exhaust relative to the rocket and the total fuel load that determines the final velocity of the rocket, and not how fast the rocket uses its fuel.   The later, as pointed out just determines the thrust ( and g forces experienced by the occupants) of the rocket) The two generally run counter to each other.

It comes down to the rocket equation:

dV = V_e ln(MR)

where dV is the final velocity change of the rocket.

V_e is the exhaust velocity of the propellant.

ln stands for the natural log

MR is the mass ratio or fully fueled rocket mass divided by the "dry mass" of the rocket.

The rate at which you use up the propellant has no effect on the final velocity, just how long it takes to reach it.

Chemical rockets, such as those we use for launches have very good thrust, but fairly low exhaust velocities. Which means they are good at lifting rockets against the pull of gravity, but have practical limits on final velocity. (you can always increase the final velocity of any rocket by adding more fuel, but at diminishing returns.  Doubling the fuel mass only increases the final velocity by 58%, and even that is assuming you don't have to add dry mass to the rocket in order to hold that extra fuel or more engine mass to lift the extra weight. Increasing your fuel load by a factor of 10 increases the final velocity by a factor of less than 3 1/2.  When it comes to launching a rocket from Earth, you reach limits as how large a rocket you can build.) 

Even in space, where you don't have to worry about "weight", too high a thrust is not a good thing.  The structure of your craft must be able to withstand the g forces that go with that thrust.  Higher thrust requires a more robust superstructure, which, in turn increases the dry mass of the ship, reducing the mass ratio and ultimately, the final velocity. 

You can get higher final velocities by increasing the exhaust velocity, but there is a catch to that also. While doubling the exhaust velocity will double the final velocity, it take 4 times as much energy to double the exhaust velocity.   There are limits to how much energy density you can get with chemical fuels, and thus limits to what kind of exhaust velocities you can achieve. 

Nuclear rockets, like the NERVA design are the next step up and are capable of an exhaust velocity  twice that of a chemical rocket, however, a typical NERVA would have a thrust of only 75,000 lbf, compared to a like-sized chemical rocket with a thrust of over 1,000,000 lbf.

Ion rockets can achieve much higher exhaust velocities, and thus attain much greater velocities for the same fuel cost, but have very low thrust.  The Dawn mission to Ceres was the first deep space probe to make use of this type of propulsion.

VASIMR (VAriable Specific Impulse Magneto-hydrodynamic Rocket) which is still under development, falls somewhere between,  better thrust than Ion, but better exhaust velocity than chemical. 

The trick is finding a energy source-engine combination that provides both a high exhaust velocity, but can also generate a significant thrust.

One possible candidate is nuclear pulse propulsion.    The earliest version of this was project Orion.  The basic idea is that you launch nuclear explosives behind you and use the explosions to propel you forward by absorbing the energy with a "pusher" plate.     Modern versions would involve detonation of small nuclear fuel "pellets" rather than full-sized nuclear bombs.   This type of propulsion is still in the theoretical stages.

It really comes down to having a high energy-density fuel source, and being able deliver that energy at a fast rate to generate significant thrust.