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Subject: Re: Do we need warp drive and large stable wormholes? (Dr. Quantum)


On Aug 24, 2010, at 4:26 PM, Jonathan Post wrote:

I'm not going on one of these things.

Glad to hear it. ;-)

But we can send practical robotic interstellar probes.

No doubt especially if they are tiny - nano-scale.

I pitched this at the United Nations, during their 50th anniversary week.
I worked backwards to figure out what stars could be reached by
starships at what velocities in order that the 100th anniversary could
be celebrated by signals (images, science data) returned from those
stars. Time dilation?  Big deal.  We correct for that in the signals by
software, as we already do for interplanetary probes (albeit a
different number of digits from the decimal point).

I mean for long trips at high gamma >>1 where (Earth time) = (gamma) (ship time) like in muon cosmic rays. There is also fact that universe is accelerating from positive cosmological constant not included in global special relativity that we have assumed here.


Shielding? The point of my design is the the frozen hydrogen is first a
structural material and shielding, then melts to be fuel, then after
fission or fusion, as reaction mass. There's no need for a whole starship to get to the destination. "Autophage" consumes itself, and leaves little more than payload at destination.


I am not doubting your multi-stage engineering increasing efficiency a bit. No doubt it can be done in this brute force inelegant fashion, but it would take too long for us personally and it would be too expensive and it simply will not happen in the foreseeable future with all the ecological crises and the financial meltdown from our string theorists inventing financial derivatives so some say. ;-)

On Tue, Aug 24, 2010 at 4:19 PM, JACK SARFATTI wrote:
This is not the way to do it
Still have time dilation & shielding issues

On Aug 24, 2010, at 1:13 PM, Jonathan Post wrote:

Dear Jack and Stardrive Forum enthusiasts,

That's exactly the oversimplification that my paper transcends.

Cf. "Feasibility of Interstellar Travel", Joffe and White I think. a
JPL document of around 1968 or 1969.  Maybe #32-225 or something like
that

I'd argued with my later co-author and co-editor Sir Arthur C. Clarke
when he came to the New York Premiere of "2001: A Space Odyssey."

So I gave him my only copy of said document when we next spoke, at
Caltech 1968 or 1969.  I read it, apologized to me, and we became
friends.

The old stupid equation assumes a 1-stage rocket.

Hello!  Ever since Robert Goddard, we've known better.  Von Braun got
it.  remember the 2-stagers we fired in the early 1950s, with V-2 as
first stage?  Or the 2-stage system he'd designed that could launch
from Peenemunde and hit New York or Washington D.C., the A-4?

One needs to Do The Math for a relativistic multi-stage rocket.  My
calculations have been checked and double-checked by others. They are
trivial to a physicist as smart as Jack Sarfatti.

Sure, the mass ratio gets huge, but as I say, the earlier stages
before the payload can carry their own payloads, get to the
destination first, and relay back data for mid-course corrections.

-- Prof. Jonathan Vos Post


On Tue, Aug 24, 2010 at 10:06 AM, JACK SARFATTI wrote:
The standard calculations are easy - too much is energy/work/fuel is needed
to get a large mass up to close to speed of light
E = (rest mass of ship)c^2(1 - (v/c)^2)^-1/2
relative to Earth base
and there will be a large time dilation, which we do not want
"In other words, on board our C-ship, we can go anywhere in the universe in
five years ship's time, though millions or billions of years may have passed
at our port of departure. As absurdly close to the speed of light as the
last few velocities may seem, and however unimaginable the energy it may
take to attain them, they're nowhere close to the speed record for material
objects in the universe. On October 15, 1991, a cosmic ray proton collided
with the Earth's atmosphere, releasing an energy of 3×1020 electron volts—as
much energy as a brick falling on your toe. To pack such energy,
this Oh-My-God particle had to be travelling at 0.9999999999999999999999951
times the speed of light, so much faster than even the maximum velocity on
our 17 billion light-year journey to the edge of the universe that the
particle would make the trip in only 19 days, compared to the 4.9 years it
took our ship."
John Walker

this is not the way it's done by UFOs if the latter are real
also there is the problem of blue shift of cosmic microwave background,
starlight, hydrogen helium atom clouds etc as the ship moves near their
local invariant light cones - requires heavy shielding of the ship - this
won't work.

"Powerplant and Engines

Our C-ship is powered by the annihilation of matter and antimatter, and can
accelerate at a sustained rate of 100 metres per second per second--a little
more than 10 Earth's gravities--to velocities arbitrarily close to the speed
of light. Most C-ship missions are unmanned: probes or lifeseeds. Manned
missions generally accelerate no faster than 1.2 gravities due to the
frailness of their cargo. The C-ship violates no known principle of physics,
but producing the antimatter consumed by a C-ship's drive in a single second
would cost, using current technology, many orders of magnitude more than all
the economies of Earth combined. But by the time our descendents are able to
make use of all the resources of the Solar System, including the entire
energy output of the Sun, they'll be able to build C-ships, albeit with a
maximum speed set by the energy available to power them.


Streamlining

C-ships are streamlined not for style, but by necessity. Space is not a
vacuum but rather a diffuse gas of relict photons left over from the Big
Bang--the cosmic background radiation with a temperature at the current
epoch of about 2.7 degrees above absolute zero. When we travel at velocities
approaching the speed of light, this radiation creates a drag on our
ship which we must minimise through radical streamlining. Interplanetary
ships may look like flying junkyards, but our interstellar and intergalactic
craft must be rapier-like to pierce the tenuous birth-cry of the universe.


Shield

Our ship is icy-white in colour for the very excellent reason that its
exterior is made of water ice, one of the most abundant substances in the
universe. When we travel at extreme velocities, dust particles impact our
ship with the energy of a nuclear bomb, and even hydrogen atoms erode her
hull. Before embarking on a mission, we re-make the surface of the ship with
ice harvested from the abundant comets surrounding the star we're departing.
During the mission, self-reproducing robots built with molecular-scale
engineering repair damage to the ice shield around our ship. The ice
protects us against impacts with interstellar and intergalactic gas and tiny
dust particles. If we hit something of tangible size, like a rock, it'll be
a really bad day; astronomers on distant planets will catalogue yet another
enigmatic gamma ray burst."

http://www.fourmilab.ch/cship/craft.html



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