1 g acceleration?

Brent Allsop (allsop@swttools.fc.hp.com)
Sun, 5 Jul 1998 18:36:52 -0600

Michael Lorrey <retroman@together.net>,

Thanks for the continued discussion on this exciting topic!

> Well, it all depends on what your propulsion system is. If you are
> using a reaction fuel based system, and are relying on internal fuel
> stores, he is right, you won't last very long.

Won't last very long? As in you'll be crushed or something?

> However, it is theoretically possible to build the interstellar
> equivalent of a ramjet that uses large magnetic fields to funnel
> interstellar hydrogen into fusion reaction chambers, the energy
> gained from which is used to propel the vehicle. Such a vehicle is
> capable of traveling across and around the entire universe at barely
> sublight speeds, and it does not rely on 'exotic' technology at all
> (exotic is a term used by physicist for classifying physical
> processes not present in the local, macro universe. Since hydrogen
> fusion is a local, macro phenomenon, it cannot be classified as an
> 'exotic' power source).

Cool! So if you can harvest or collect the fuel and mass to use for acceleration as you go this makes a difference from if you start with your fuel and mass on board?

> 1 g is 32 feet per second per second, or 9.8 meters per second per
> second

I guess I should have looked that number up instead of just pulling the incorrect constant 13 out of my head. But at least you knew what I was getting at.

> > If you were orbiting, at near the speed of light, just above the
> > event horizon, wouldn't you feel weightless?
> No, you would feel rather strained, to say the least....

This can't be right can it? It is possible to orbit around a black hole isn't it, if you are far enough away? And if you are at an orbital velocity, then you'll be weightless right? Or as if you are not accelerating since the centrifugal force precisely counteracts the gravity, at least outside the event horizon. As you approach the event horizon, the speed required to maintain enough centrifugal force to counteract the gravity increases. But, as long as one is above the event horizon, the right sub light speed is all that is required for this unless I'm mistaken. It's my understanding that the definition of the event horizon is the point at which the speed of light is required to achieve enough centrifugal force to balance the pull of gravity at that point. I know you must at least be wrong with this statement if you define "near the speed of light" as say a typical speed for the space shuttle in low earth orbit and "just above the event horizon" to be far enough away so as there is the same amount of gravity pull as the shuttle would experience in this same low earth orbit right?

Or perhaps the "strained" you are talking about is that from the force of the engines accelerating you to the speeds near light required to keep you in orbit close to the event horizon? But this doesn't seem right either. Doesn't something in a higher orbit contain more potential energy than something in a lower orbit? Mustn't one find some way to shed this potential energy in order to move from a higher orbit into a lower orbit? As in de-accelerate? Which I guess causes a sensation of gravity just like acceleration. But couldn't you maintain your descent, and shedding of this potential energy at or under 1g all the way tell you get close to the event horizon? I sense I'm loosing my grasp on physics at this point, where am I going wrong? If this were all true it would be easy for someone to get to the speed of light, at least in orbit around a black hole. Or would it just take you forever to bleed off that much potential energy at a constant 1 g deceleration and you would never reach the event horizon before running out of deceleration propellant or something? I love the way friction causes a coin to stay in an ever decreasing yet speeding up orbit in one of those charity thingies. Couldn't you catch infalling interstellar hydrogen in you're "interstellar equivalent of a ramjet"?

Brent Allsop