From: Brent Allsop (allsop@swttools.fc.hp.com)
Date: Sun Jul 05 1998 - 18:36:52 MDT
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
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