
The Physics of Building a Black Hole Powered Starship [pdf] - awwx
http://arxiv.org/pdf/0908.1803v1
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nicara
"It is now known that any prolonged human presence deeper in space would need
to be behind a shield of the effective strength of two feet of lead, which
would weigh 400 tonnes for a small capsule."

Uhm, the first thing that comes to my mind - regardless of whether this black
hole propulsion might actually work - is the amount of lead we have available.
Just building the spaceship seems to be just as much a problem as accelerating
it..

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hegemonicon
The world is a big place - annual lead production is approximately 7 million
metric tons.

Source: [http://www.financialexpress.com/news/lead-uses-that-go-
back-...](http://www.financialexpress.com/news/lead-uses-that-go-back-
over-5-000-years/179609/)

~~~
nicara
Sure, and I admit I have no idea how much lead building such a spaceship might
take, but keep in mind 2 things:

1) "More than half of the lead currently used comes from recycling." (from
your article) - Once the spaceship is built and has left Earth, the lead is
essentially gone (for the time being), so the more of those we build, the
fewer lead we will have to recycle, and it will get even more difficult to
build additional ones.

2) 400 tons for a small capsule, and consider they're proposing a spaceship in
which multiple people could live in _autonomously_ , i.e. they need places to
live in, but also room to grow food, process their waste, etc. So I'd guess
it's much higher than you seem to have assumed.

Oh and btw, I'm fairly certain we also need much of that lead on earth - hence
why we're producing so much of it in the first place, so it's not like we have
some spare lead in the order of magnitude of, say, 10000s (I'm really just
guessing here, though) of tons lying around collecting dust.

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pyre
I assume that we'll somehow solve this one with a 'force' field of some sort
in the future. Think about it. The Earth isn't surrounded by lead, but we are
still protected from the radiation. I imagine that if we can harness a black
hole for propulsion we can somehow use it for power too??? Then we just use
some of the power to create a magnetic field that blocks/reflects/deflects the
radiation.

~~~
science4sail
> The Earth isn't surrounded by lead, but we are still protected from the
> radiation.

A thick atmosphere accomplishes roughly the same effect as a few feet of lead.
A magnetic field could deflect incoming charged particles, but I'm not sure if
a "shield" is feasible, due to any side effects that such a magnet might have.

~~~
pyre
I was under the impression that the Earth's magnetic field was doing the
majority of the work. IIRC, the reason that Mars has no atmosphere is probably
due to lack of a (or just a weakened) magnetic field, causing solar winds to
strip away the atmosphere.

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bioweek
They don't seem to mention how to contain the black hole. What holds its
position steady within the spaceship?

If we made a large enough one say 1/2 earth mass, we'd get free "artificial"
gravity on the spaceship.

~~~
bioweek
I meant, how do you stop the black hole from hitting the spaceship, moving
around, falling out the back, etc?

~~~
awwx
They touch on this briefly at the top of page 11: "The most optimistic
approach is to solve requirements 2 [accelerate the black hole to keep it with
the ship] and 3 [feeding the black hole with matter so that it doesn't
evaporate] together by attaching particle beams to the body of the ship behind
the BH and beaming in matter. This would both accelerate the SBH, since BHs
“move when you push them” (see [3] p270), and add mass to the SBH, extending
the lifetime."

The engineering details are left as an exercise for the reader :-)

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bitwize
I saw this headline and flashed back to the Gunbuster Science Lessons.

"Dimensional Wave Super String Excitation Degenerated Radius Jump
Gravitational Field Super-light Speed Navigation. WARP for short."

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caffeine
This is really, really cool. And this is obviously how they powered Rama.

