Starship Asterisk*

starnut wrote: Remember what happened to the space shuttles Challenger and Columbia? Using chemical rockets to leave the Earth and atmospheric braking to return is too dangerous and inefficient. It also takes far too long to get the shuttle ready for the next flight. Better to be able to control gravity to take off and land gently. We can also use gravity control for air travels.

Still, we go to and from space regularly. It's not the problem, and waiting for anti gravity is not the way, since there is nothing to indicate that it is anywhere close to happening.

starnut wrote: Accelerating to near light speed is not the only problem. Decelerating when reaching your destination is another problem that also requires a lot of energy. Then there is the time dilation problem.

Acceleration and deceleration is the same thing.

starnut wrote: Rotating a spaceship to create artificial gravity also creates all kinds of engineering problems, such as maintaining balance when internal loads shift from one side to another and stopping and restarting the rotation in order to do exterior maintenance during spacewalks. Then you need a non-rotating section for navigation, ingress and egress purposes.

Gary

Those are minor issues.

You don't really need a non-rotating section.

You can let the the whole ship rotate, once it's done accelerating, and doesn't need much navigation for the rest of the trip, until accelerating to a stop again.

The shop would likely be accelerating for a very long time, maybe close to half the way, before "decelerating". During acceleration, you have gravity, due to the acceleration, so in that case, you don't need any rotation at all.

The best solution, in my book, is to create an engine that produces a constant 1G thrust. Susatined 1G supplies the gravity and constant thrust supplies the speed. You would simply need to shut down the engines at the 1/2 way point, thruster turn the ship 180deg and then fire up the engines again. The constant 1G breaking thrust would again provide the gravity while slowly breaking to your destination. The trick is that the engines would need to be electrical as opposed to chemical.

BMAONE23 wrote:The best solution, in my book, is to create an engine that produces a constant 1G thrust. Susatined 1G supplies the gravity and constant thrust supplies the speed. You would simply need to shut down the engines at the 1/2 way point, thruster turn the ship 180deg and then fire up the engines again. The constant 1G breaking thrust would again provide the gravity while slowly breaking to your destination. The trick is that the engines would need to be electrical as opposed to chemical.

right, that is a good solution for traveling within our solar system.

But to other stars, 1 g is too little

http://www.daviddarling.info/encycloped ... craft.html
It could also work outside the solar system thanks to time dialation

soupphysics wrote:
Still, we go to and from space regularly. It's not the problem, and waiting for anti gravity is not the way, since there is nothing to indicate that it is anywhere close to happening.

I don't think that you would be so dismissive of the risk of continually using chemical rockets if we have more accidents like the Challenger and Columbia tragedies. Each time, those accidents resulted in the complete shutdown of the manned space flights by the U.S. for several years while NASA worked to prevent their re-occurrences. We had to depend on the Russians for resupplying the ISS after the Columbia disaster. That is why I am hoping the the LHC or any other particle accelerator would enable us to understand the nature of the gravitational force and a way to control it, like we are able to control electromagnetism.

soupphysics wrote: Acceleration and deceleration is the same thing.

Yes, and each requires corresponding amount of fuel/energy to perform. And you will also need to carry additional fuel for the return trip.

starnut wrote: Rotating a spaceship to create artificial gravity also creates all kinds of engineering problems, such as maintaining balance when internal loads shift from one side to another and stopping and restarting the rotation in order to do exterior maintenance during spacewalks. Then you need a non-rotating section for navigation, ingress and egress purposes.

soupphysics wrote: Those are minor issues.

You don't really need a non-rotating section.

You can let the the whole ship rotate, once it's done accelerating, and doesn't need much navigation for the rest of the trip, until accelerating to a stop again.

The shop would likely be accelerating for a very long time, maybe close to half the way, before "decelerating". During acceleration, you have gravity, due to the acceleration, so in that case, you don't need any rotation at all.

I don't think they would be consider "minor" from engineering point of view. And you do need a non-rotating section if you are orbiting a planet and wanting to send out a shuttle craft without stopping the rotating section. Of course, we could put the docking port at the front end like the space station in "2001: A Space Odyssey."

Gary

While in college (decades ago), I once wrote a computer program using the Special Theory of Relativity, to compute and list the changes (to an outside observer) in a spacecraft's physical attributes as it accelerated constantly at 1g until it reached 99.9% of the speed of light. It would take the spacecraft almost one year to reach that speed. I don't remember how the distance it would travel to reach that speed. During the voyage, its relativistic length would contract and its relativistic mass would increase. One thing I was not sure about when writing the program is whether the steady increase in relativistic mass would require even greater amount of energy to maintain the constant 1g acceleration. The mass of the spacecraft with its fuel does not increase in its proper frame.

Gary

starnut wrote: I don't think that you would be so dismissive of the risk of continually using chemical rockets if we have more accidents like the Challenger and Columbia tragedies. Each time, those accidents resulted in the complete shutdown of the manned space flights by the U.S. for several years while NASA worked to prevent their re-occurrences. We had to depend on the Russians for resupplying the ISS after the Columbia disaster. That is why I am hoping the the LHC or any other particle accelerator would enable us to understand the nature of the gravitational force and a way to control it, like we are able to control electromagnetism.

Irrelevant! This is not what is preventing long space trips and anti gravity isn't either.

starnut wrote: Yes, and each requires corresponding amount of fuel/energy to perform. And you will also need to carry additional fuel for the return trip.

I don't know why you are telling me this, which I obviosly already know. I am the one who told you that this is what you need energy for, and that antigravity doesn't help you.

starnut wrote: I don't think they would be consider "minor" from engineering point of view. And you do need a non-rotating section if you are orbiting a planet and wanting to send out a shuttle craft without stopping the rotating section. Of course, we could put the docking port at the front end like the space station in "2001: A Space Odyssey."

Gary

No, there is no need for rotation while orbiting. Orbiting is the least part of the problem. You can also easily enough dock while rotating if you want to.

starnut wrote:While in college (decades ago), I once wrote a computer program using the Special Theory of Relativity, to compute and list the changes (to an outside observer) in a spacecraft's physical attributes as it accelerated constantly at 1g until it reached 99.9% of the speed of light. It would take the spacecraft almost one year to reach that speed. I don't remember how the distance it would travel to reach that speed. During the voyage, its relativistic length would contract and its relativistic mass would increase. One thing I was not sure about when writing the program is whether the steady increase in relativistic mass would require even greater amount of energy to maintain the constant 1g acceleration. The mass of the spacecraft with its fuel does not increase in its proper frame.

Gary

Seen from the ship itself, no energy increase is needed to keep the acc of 1g.

Seen from a stationary (relative to the ship), the acc. would be less and less if the energy was no increased

If the Mass of the ship increases as speed reaches C wouldn't also the mass of the fuel increase although it is being used? and couldn't the proportional thrust increase as a result?

The energy in the fuel would not increase, so neither would the thrust.