On Wed, Sep 27, 2017 at 05:51:27AM +0000, Thomas Jones-Low wrote:
> On 9/27/2017 1:41 AM, Richard Aiken wrote:
> > On Wed, Sep 27, 2017 at 1:33 AM, Richard Aiken <xxxxxx@gmail.com> wrote:
> >
> > > I know that the force of gravity drops with distance from the center of
> > > mass. If a 1-G streamlined ship aerodynamically flies up to maximum
> > > altitude (e.g. as high as winged lift can take it), would the force of
> > > gravity become low enough for it to boost into orbit from there?
> > >
> > >

IIRC, gravity at R_earth + 250km is about 9.4 m/s^2 but that's me
looking at the output of computer program who's primary purpose isn't
to measure that at all.

> >
> > Google tells me that most military aircraft have service ceilings in excess
> > of 50,000 feet.
> > It also tells me that a mass of 150 pounds actually weighs ~149.92 pounds
> > at 10,000 feet elevation.
> > So . . . maybe the ship can just barely make it?
> >

I'm fairly certain that the reduction in gravity isn't a factor that
low. Even wih those numbers you are looking at a 0.06% reduction.

> 	An aircraft with much less that 1G of thrust can get to 50,000 feet. But
> the problem isn't height, it's velocity. At lower altitudes the air
> resistance will prevent the ship from getting enough velocity. At higher
> altitudes there may not be enough air to provide more lift. Oxygen for the
> engines isn't a problem for a space ship.
>
> 	I think the answer is yes, but for a different reason.

Also, aircraft attain altitude mainly from the lift that their wings
generate. Fighter aircraft can generally tailstand but even an F-15
couldn't tailstand from surface to the Karman line.

This does bring up another possiblity though. On a size 8 planet,
there could be a ferry service that took you above the thick part of
the atmosphere and to a pretty high velocity via either grav, or aero
and then released you such that you could get to orbit. Sounds like it
comes with a bigger risk thank a Vilani would take though.

--
Chris

      __o          "All I was trying to do was get home from work."
    _`\<,_           -Rosa Parks
___(*)/_(*)____.___o____..___..o...________ooO..._____________________
Christopher Sean Hilton                    [chris/at/vindaloo/dot/com]