Most likely candidate for future spaceship propulsion

[Gardamorg]

Originally Posted by Moontanman

Friction with the air is what slows down a missile,

That and it's weight pulling it down.

once in space an object free of the earths gravity or the suns gravity will continue to move until it is acted on by another force.

It won't be free of it's own mass though. Only particles are free of their own mass.

No matter how massive it is. Speed only increases mass or weight when you are close to the speed of light.

Correction, mass decreases the speed of an object as it approaches the speed of light.

[Moontanman]

Gardamorg are you trying to be a troll? I was trying my best to help you, being a troll is not nice

[Gardamorg]

Originally Posted by Moontanman

Gardamorg are you trying to be a troll? I was trying my best to help you, being a troll is not nice

When did I troll?

[Moontanman]

Originally Posted by Gardamorg

When did I troll?

By claiming things to be true when you know they are patently false. I've read enough of your threads to know you have been shown that objects get more massive not less massive as they get near the speed of light, I know you know an object does not slow down by its self, I know you know an object's mass doesn't have anything to do with it's ability to keep moving when in free fall. I know you know a magnetic field doesn't affect neutral particles. I gave you link to Newtons Laws but you ignored it. If you don't want me to point out your mistakes then just say so and I'll not post in this thread anymore.

[Gardamorg]

Originally Posted by Moontanman

By claiming things to be true when you know they are patently false. I've read enough of your threads to know you have been shown that objects get more massive not less massive as they get near the speed of light,

Which is what my whole argument is about, it gets so massive that it's speed decreases because it's thrust can't push it anymore.

I think you know an object does not slow down by its self, I think you know an object's mass doesn't have anything to do with it's ability to keep moving when in free fall.

Corrected.

I know you know a magnetic field doesn't affect neutral particles. I gave you link to Newtons Laws but you ignored it. If you don't want me to point out your mistakes then just say so and I'll not post in this thread anymore.

If you think you know all this about me, your gravely mistaken.

I've ALWAYS known an object's mass increases as it moves faster, which is why an object is constantly trying to stay still.

[Moontanman]

Originally Posted by Gardamorg

Which is what my whole argument is about, it gets so massive that it's speed decreases because it's thrust can't push it anymore.

This is only true very near the speed of light and it doesn't make the object slow down just makes it harder to go faster.

Corrected.

Thank you

If you think you know all this about me, your gravely mistaken.

I've ALWAYS known an object's mass increases as it moves faster, which is why an object is constantly trying to stay still.

No, an objects mass only increases very near the speed of light, at much slower speeds this is not true and even close to the speed of light an object is only difficult to accelerate , it does not naturally slow down. Even an object very close to the speed of light will continue on at that speed until an outside force acts on it. In theory it could coast at 99.999999999% of the speed of light forever.

[CraigD]

My vote is for beam-powered propulsion.

There are many possible versions of this approach. My favorite is the Robert Forward type laser-pushed lightsail, but others may well prove more feasible, including the charged particle-pushed magnetic sail Moontanman voted for. Other versions (not mentioned in the wikipedia article, but described in various other sources), commonly referred to as “fountains”, transfer momentum via bullet-like, uncharged, non-light particles.

All of these approaches, with the exception of very low-mass vehicles like Forward’s Starwisp, require the construction and operation of solar-system space based solar energy and beam generating facilities not only many times more massive than the vehicle they propel, but many times more massive than all of the vehicles launched into space in the history of mankind. Such large, in depth programs are, IMHO, the best long-term approaches to spaceflight.

PS: Gardamorg, Moontanman’s efforts to instruct you in the fundamental laws of motion are correct. I fear you’ve gotten too much of your thinking about spaceflight from popular science fiction, such as Star Trek, Star Wars, and Battlestar Galactica, in which spacecraft are depicted as behaving similarly to water surface ships, which make no headway when not under power. Real spacecraft, including all those launched to date, such as the Voyager spacecraft, the most distant manmade objects to date, are powered only briefly, when lifted from Earth, making course corrections, and inserting into orbit around, or landing, or impact with their target bodies.

[Gardamorg]

Originally Posted by CraigD

My vote is for beam-powered propulsion.

There are many possible versions of this approach. My favorite is the Robert Forward type laser-pushed lightsail, but others may well prove more feasible, including the charged particle-pushed magnetic sail Moontanman voted for. Other versions (not mentioned in the wikipedia article, but described in various other sources), commonly referred to as “fountains”, transfer momentum via bullet-like, uncharged, non-light particles.

All of these approaches, with the exception of very low-mass vehicles like Forward’s Starwisp, require the construction and operation of solar-system space based solar energy and beam generating facilities not only many times more massive than the vehicle they propel, but many times more massive than all of the vehicles launched into space in the history of mankind. Such large, in depth programs are, IMHO, the best long-term approaches to spaceflight.

PS: Gardamorg, Moontanman’s efforts to instruct you in the fundamental laws of motion are correct. I fear you’ve gotten too much of your thinking about spaceflight from popular science fiction, such as Star Trek, Star Wars, and Battlestar Galactica, in which spacecraft are depicted as behaving similarly to water surface ships, which make no headway when not under power. Real spacecraft, including all those launched to date, such as the Voyager spacecraft, the most distant manmade objects to date, are powered only briefly, when lifted from Earth, making course corrections, and inserting into orbit around, or landing, or impact with their target bodies.

Oh...

[CraigD]

Originally Posted by Moontanman

No, an objects mass only increases very near the speed of light, at much slower speeds this is not true and even close to the speed of light an object is only difficult to accelerate , it does not naturally slow down.

This is nearly, but not exactly correct. Bodies traveling even at very low speeds relative to an observer. For example, a 100 kg man walking at a typical speed of 1 m/s actually masses

That is, he gains about 625 nanograms - about the mass of a single human egg cell, or a small grain of sand.

Originally Posted by Moontanman

Even an object very close to the speed of light will continue on at that speed until an outside force acts on it. In theory it could coast at 99.999999999% of the speed of light forever.

This is true only if the object is traveling in a perfect vacuum.

Interstellar space contains has a density of about 1 hydrogen atom per 1 to 10 cubic centimeters, or about to From this, you can calculate the power per unit area of friction for a spacecraft traveling in it as
.
Calculating this for the lower density for craft traveling at 0.1 c (As Janus did in post #32 of “Quickest way to get to The Super Earth”) gives a small, but troubling from a practical engineering perspective, . Calculating it for 0.99999999999 c gives about 500 million!

To put this into some kind of perspective, if the spacecraft used a plug of water ice near absolute zero as frontal shielding, this shield would be vaporized at a rate of about 3.2 meters of thickness per second!

In terms of conservation of momentum, ignoring the practical engineering problem of shielding and cooling, the density of interstellar space would produce an acceleration of

Even for a tiny spacecraft massing only 1000 kg with an frontal area of , traveling 0.99999999999 c, this calculates to about . In about 1 year, it would slow by about 3 m/s, to a speed of about .99999999 c. Friction would never completely stop it relative to the interstellar medium, but over the decades and centuries, would keep knocking 9s off of its speed as a fraction of c. Using numeric approximation methods, we can calculate its speed in about 1 year as 0.99999999 c, 0.9999999 c in about 100 years, 0.999999 c in about 10,000 years, and about 0,999 c in about 10 billion years, roughly the current age of the universe.

[Moontanman]

Originally Posted by CraigD

This is nearly, but not exactly correct. Bodies traveling even at very low speeds relative to an observer. For example, a 100 kg man walking at a typical speed of 1 m/s actually masses

That is, he gains about 625 nanograms - about the mass of a single human egg cell, or a small grain of sand.This is true only if the object is traveling in a perfect vacuum.

Interstellar space contains has a density of about 1 hydrogen atom per 1 to 10 cubic centimeters, or about to From this, you can calculate the power per unit area of friction for a spacecraft traveling in it as
.
Calculating this for the lower density for craft traveling at 0.1 c (As Janus did in post #32 of “Quickest way to get to The Super Earth”) gives a small, but troubling from a practical engineering perspective, . Calculating it for 0.99999999999 c gives about 500 million!

To put this into some kind of perspective, if the spacecraft used a plug of water ice near absolute zero as frontal shielding, this shield would be vaporized at a rate of about 3.2 meters of thickness per second!

In terms of conservation of momentum, ignoring the practical engineering problem of shielding and cooling, the density of interstellar space would produce an acceleration of

Even for a tiny spacecraft massing only 1000 kg with an frontal area of , traveling 0.99999999999 c, this calculates to about . In about 1 year, it would slow by about 3 m/s, to a speed of about .99999999 c. Friction would never completely stop it relative to the interstellar medium, but over the decades and centuries, would keep knocking 9s off of its speed as a fraction of c. Using numeric approximation methods, we can calculate its speed in about 1 year as 0.99999999 c, 0.9999999 c in about 100 years, 0.999999 c in about 10,000 years, and about 0,999 c in about 10 billion years, roughly the current age of the universe.

Thanks Craig, notice I did say theoretically, the interstellar medium is as much a barrier to near speed of light travel as the problem of accelerating to near light speed. Arthur C. Clark took this into consideration in the book Songs Of Distant Earth, the space craft used zero point energy to travel very close to the speed of light but it had to have a huge shield of ice to keep from being destroyed by the interstellar gas turned into cosmic rays by the ships speed. Even grains of dust caused huge craters on the shield. I'm not sure how to figure it but I'm sure there is a point of trade off where speed becomes deadly and it is probably considerably less than .99999 c