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Re: Fwd: LIT e-mail discussion group
Ok, here my first cut of a summary of all the options we've come up with.
(or at least all I can remember.) I figure this is the next step up from
Zenons proposed table of contents. We might want to work this up to a
summary or central reference page for the LIT server. (More detailed
secoundary pages could brach off it.) I'll do more as I get some time. (I
working to finish the first draft of my secound novel! So I'll be
preoccupeid)
Please review and comment.
Kelly
============================================================
Mission flight type
---------------------------------
One-way
* Suicide (explore and die before your time when supplies end)
* One-way (Enough supplies are shipped to stay in target system until
natural death)
(For some inexplicable reason this option has one or two strong advocates
within L.I.T.. I want it absolutely known that I neither approve or in
anyway support such an option. Nor would I in any credible situation
expect it to generate anything but revulsion among the general tax paying
public. Kelly Starks - The Author.)
>Pros
The ship need only be designed for a one time, one way flight. This limits
the technical mission risk and requires less resources.
Least likelihood of back contaminating Earth.
Establishes temporary outpost in starsystem.
Allows investigation of the starsystem to continue until al exploration
resources are exhausted or worn out. Presumably for a decade or so,
depending on the service life of the shuttles or their support facilities,
or the service life of the remotes.
>Cons
To put it mildly the public acceptance of sending explorers out to die the
mission and die on the frontier is low. Risking dying maybe, but
assigned/left to die by superiors -- no way. Every politician within ear
shot will run in front of the closest camera to announce that he or she
will personally lead the witch-hunt to track down everyone connected with
suggesting this idea.
It has been suggested (adamantly) by some members of the group, that this
might be justifiable under some situation, or that this would be acceptable
as a colonization mission, especially if the colony could be made
completely self sufficient from the start. Aside from the technical
impossibility of doing the latter. Its unlikely in the extreme, that such
risks would be acceptable in an initial mission. At the very least the
mission would have to be designed as a two way flight with the option of
founding a colony or outpost. Also their would be considerable debate as
to why we would want to set up a permanent outpost in a place we don't know
anything about, and have no idea if we'd want to stay at. This debate
would get louder when the continuing cost of supply flights was discussed.
Other problems would be:
The potential supply of skilled personnel would obviously drop, if they
knew they were to be abandoned in the system when they finished the
mission. Especially given that their project life expectancy (due to the
lack of 'modern' medical facilities) would drop by a few decades, all but a
few years of which they'd spend trapped in a traveling, or derelict ship.
Lower information return to Earth due to limited baud rates of interstellar
communication.
Projected types of crew termination
- Voluntary suicide at end of exploration phase of mission.
This is likely as some crewmen decide to avoid living out the rest of their
years imprisoned in a derelict ship.
- Death due to catastrophic failure of vital ship systems as the ship
wears out.
Obviously the ships systems won't last forever, and can't be rebuilt or
replaced completely. At some point it will simply wear out and fail. This
could be a single failure, like a major structural breach of the habitation
or support systems due to metal fatigue. Or a accumulation of lesser
failure as sub-systems begin to unravel.
- Death due to medical limitations.
Given the limited medical facilities and personnel available on the ship.
Crew life expectancies would be far less than those who stayed at home with
access to modern medical care. Given the mid 21st century high-tech
population would conservatively have a projected life expectancy of 100-130
years, with elongated vigorous years. (Some estimates are far higher.)
The crews limited medical life expectancy may still be nearly current US
norms.
- Death due to chronic crew failure.
At some point the crew will simply be to old to maintain and operate the
ship, or provide their own medical care. At this point, without a follow
on generation to rescue or care for them, they will slowly or quickly die
off due to a combination of the above listed causes.
---------------------------------
Round trip (Crew returns to Earth with ship at mission end.)
>Pros
Simplest option, and one with little likely hood of public objection.
More likely to get more volunteers and better qualified volunteers for flight.
This option implies that the mission is fairly short. I.E. within the
professional life of the crew. This would imply its short enough to return
information in a useful amount of time. (I.E. it would get there and back,
before a later faster flight could do it.)
It would return far more information than an interstellar communications
link could manage.
It obviously avoids the grisly public relations and crew morale problems of
a one way mission.
>cons
Technically more challenging. Getting a ship to the target starsystem is
hard enough. Getting it back would make it harder. But this must be
traded off against the added complexity of a ship capable of supporting its
crew for the rest of their lives.
It has to be a fast enough ship to get back in an acceptable amount of
time. To slow and theirs no practical reason to send it.
---------------------------------
Pick up and return by follow on flight
>Pros
Most of the advantages of the round trip model, and would allow the first
ship to be a mobile research station or other specialized ship, with faster
courier ships providing round trip flights.
>cons
High risk and more complicated. Multiple ship types, and concerns that the
first ship might be left stranded.
---------------------------------
Crew constructs equipment for return flight
This option come up with light/microwave sail craft, beamed power craft,
and fuel launcher craft. The crew would construct automated duplicates of
the systems that launched the ship from Sol space.
>Pros
Would establish launcher facilities in both star systems. Which could
allowing faster two way flights with specialized fast light ships.
The crew might get back faster with their ship using the constructed
launcher systems for assistance.
cons
If they can't build the equipment, they don't get home.
The construction phase may require so many resources that the first flight
is devoted just to infrastructure construction. With little or no
exploration being done in the first mission. This obviously would cool
public interest and slow down the return of productive information.
---------------------------------
Multi-step. (Ship proceeds to other target star after completion of first
mission, in first starsystem.)
>Pros
One mission explores multiple star systems.
>cons
Technical feasibility is low since wear and tear on the ship would
accumulate, dramatically increasing the likelihood of a catastrophic
failure.
Because of the extremely long flight times with likely technology, the
mission would take so long as to be undesirable. At some point the ship
would be superseded by newer faster ships sent straight out from earth,
decades after its launch.
---------------------------------
Multi-generation Succeeding generations of crew continue the mission
>Pros
This is the one of the standard concepts suggested to get around the
extremely long flight times.
Could allow extremely long flight times.
cons
The ship would have to be huge to support the active crew,
retired/incapacitated crew, children, and all the extra support facilities
and personnel they would require.
The crew, ship, and equipment would need to be even larger than that to
allow them to be able to completely rebuild the ship from the inside out as
it, and its systems, exceeded their service lives.
Any ship that takes that long to get to where it wants to go, will probably
find it gets there after newer faster ships from earth. So their is little
reason to launch it.
The flight would take so long few people would be enthusiastic in launching
it, even if they didn't consider the likelihood of faster follow on craft.
I.E. why spend money on something you'll never see the results of, nor even
ever know if they made it.
The follow on generation(s) in the ship will have no allegiance or
commitment to the mission or its originators (they, never agreed to
anything).
The follow on generations would have no hands-on experience with the
exploration systems they would be expected to use. Or for that matter, any
experience with planets and starsystems.
Its harder to get qualified people to go on such a flight. People who want
to explore wouldn't want to spend the rest of their life stuck in a ship,
knowing they will never contribute anything but their genes.
---------------------------------
Hibernation flight
>Pros
This is the other one of the standard concepts suggested to get around the
extremely long flight times.
The ship would not need to support the inactive crew.
The crew wouldn't need to spend years of their lives waiting around in the
ship with nothing to do until they get to the star system.
The crew will still be fresh and familiar with their jobs when then are
waken up in the star system.
>cons
The ship systems will still exceeded their service lives, but their may not
be enough people around to service them. The sleepers could wind up dying
on route as the ship died around them.
The sleepers would have to be extremely well shielded from radiation, since
their cell repair mechanisms would be as dead as they are.
Any ship that takes that long to get to where it wants to go, will probably
find it gets there after newer faster ships from earth.
The flight would take so long few people would be enthusiastic in launching it.
technical political Desirability
Risk Feasibility risk Feasibility
-------------------------------------------------------------
One-way med-low Medium Ex-high Nil Low
Round trip medium medium low High high
Pick-up Med-high medium medium medium medium
Construct ret high med-high medium medium medium
Multi-step Ex-High. med-low low Medium medium
Multi-gen Ex-high Low high medium low
Hibernation high Low medium medium low
-------------------------------
============================================================
Alternatives
---------------------------------
robotic fly by's
>Pro
Could use a smaller lighter ship and could tolerate longer flight times.
>Con
requires extremely good A.I. systems and reliability (which may or may not
be likely by 2050), and would generate far less public interest.
Why bother, you could do nearly as well with huge telescope systems in the
Sol star systems
---------------------------------
Robotic exploration
>Pro
Could use a far smaller lighter ship and could tolerate longer flight times.
>Con
Again requires extremely good A.I. systems and reliability, and would
generate less public interest.
Would be less capable than a manned mission.
============================================================
Mission purpose
---------------------------------
Colonization of planets or moons
>Pro
Very popular idea with public.
Excellent staging area for direct examination of that planet or moon.
>Con
Expensive. Either the colony would need to be the size of a major city to
support all of the specialists needed to support a self sustaining society,
or regular (extremely expensive) supply flights from earth would be
necessary.
On a planet with a Earth-like ecology it would be a biological death trap.
Alien microbes, allergens, and other unknowns life forms would easily
defeat unprepared Earth mammalian immune systems.
On a planet with a non-Earth-like ecology it still could be a biological
death trap, and in addition have basic climate and biosphere
incompatibilities (Wrong temperatures, air pressures, gravity).
Isolation from resources. Ores, energy and raw materials are far harder to
access on a planet than in space.
Isolation from other planets.
Their doesn't seem to be enough practical justification for such a massive
undertaking.
---------------------------------
Colonization of constructed space platforms
>Pro
Still may be a very popular idea with public.
Excellent staging area for examination of the solar system.
Much lower biological threat than on a planet with biosphere.
The internal gravity, radiation, and environment can be precisely tailored
to humans.
Far easier to construct and service than a planet bound colony.
Easy access to plentiful resources. (Space is considered so much richer in
cheap, easy to access resources and power. That it is expected that
Earth's heavy industry will migrate into space in the next century.)
Could act as a servicing center and supply port for the starship, or
subsequent starships.
>Con
Expensive. Either the colony would need to be the size of a major city to
support all of the specialists needed to support a self sustaining society,
or regular (extremely expensive) supply flights from earth would be
necessary.
Their doesn't seem to be enough practical justification for such a massive
undertaking.
---------------------------------
Infrastructure construction
>Pro
This could establish facilities necessary for routine, lower cost, flights
between home and this starsystem.
>Con
Construction could take so many resources that little or no exploration
will be done.
Less interesting to public than an exploration or colony program.
Could be very expensive.
--------------------------------------------------
============================================================
propulsion systems
---------------------------------
Fusion feed from internal fuel sources.
A fusion powered rocket could cross interstellar distances, and is a near
term enough technology to be considered likely for the mid 21st century.
Unfortunately the amount of fuel it takes to get such a ship up to a usable
speed (at least 1/5th of light speed is necessary. More than a 1/3rd is
highly desirable.) is not carryable by such a ship. Since the fuel would
weigh hundreds to thousands of times as much as the rest of the ship.
For example for a fusion rocket with a specific impulse of 1,000,000. If
you wanted to use such an engine to accelerate a ship up to 1/6th the speed
of light. The ship would need to carry 147 times its dry weight in fuel.
If you want to get to 1/3rd the speed of light, it would need to carry
22,000 times its weight in fuel! Obviously no realistic ship could do
this.
(Note: a specific impulse of 1,000,000 (A exhaust velocity of
10,000,000m/s) means that the engine gives 1,000,000 pounds of thrust, for
one second, for every pound of fuel consumed. This has long been
considered a very do-able fusion performance number. For comparison the
best chemical engines have a specific impulse of 455.)
---------------------------------
Staged fusion ship
You start with a 1 billion ton fueled ship cluster driven by a 10 million
ton engine and support structure (yeah right.). That engine is powerful
enough to push the whole mess with an acceleration rate of 10m/s.
When you burn off 95% of your weight in fuel. The ship cluster weighs 50
million tons, 20% of which is a first stage engine/structure that's WAY too
powerful. You throw the first stage away and start a smaller second stage.
It weighs about 400,000 tons (about as much as 4 aircraft carriers) and
can push the 40,000,000 ton ship cluster. When you burn that down to
2,000,000 tons of cluster you throw that away that stage for a 70,000 ton
ship with 5-10,000 tons of drive systems. Which can use the remaining
390,000 tons of fuel to get itself into the system.
stage total weight (tons) thruster pack and stage structure
1 1,000,000,000 10,000,000
2 40,000,000 400,000
3 2,000,000 70,000 ton ship
with 5-10,000 tons of
drive systems.
This assumes a 100 to 1 thrust to weight ration for a fusion drive systems
(which is questionable), and once you get where your going, coming back is
out (unless of course you scale the craft up accordingly). But it would
give us huge fuel ratios for relativistic flight. So, in theory, a Multi
stage fusion craft could get to the star. Assuming of course you can find
a billion tons of fusion fuel, and a ship yard in space that can construct
a ship the size of an asteroid! Which means in practice the ship is
unbuildable.
These numbers of course assume the ship has to carry the weight of its
fuel. Obviously craft normally have to carry their fuel, but their are
some ways around it.
---------------------------------
Fusion with externally feed fuel sources
A fuel launcher is a linear accelerator mounted somewhere in our solar
system. It throws the fuel out in front of where the ship is going to fly.
The ship scoops up the fuel as its going along. This has several
advantages. The ships engines only need to accelerate the ship itself.
(They don't even have to adjust for changing ship weights.) The fuel is
accelerated up by the launcher. This means the launcher system (who's
power comes from unaccelerated fuel) takes up a large fraction of the load,
and the ship saves a lot of energy.
Problems are that unless the ship is flying to a starsystem with a
operating fuel launcher. It can't fly any faster then a speed it can
decelerate from using its onboard fuel reserves. Also, this only works
when your close enough to the launcher that it can accurately launch the
fuel to you. Once your out of range, your stuck with fuel your caring.
Fuel launchers (or beamed power) have the advantage of eliminating the need
for the ship to carry the heavy fuel (and power systems). That improves
the ships power to weight ratio significantly. But the systems are
difficult to do, limit range, and don't seem to help us to slow down.
Beamed power
Beamed power (or fuel launchers) have the advantage of eliminating the need
for the ship to carry the heavy fuel (and power systems). That improves
the ships power to weight ratio significantly. But the systems are
difficult to do, limit range, and don't seem to help us to slow down.
Beamed power systems are most effective as microwave sail craft. But
powered electromagnetic drives are possible also.
Anti-matter
Can be destroyed to create tremendous amounts of energy. Releases over a
hundred times as much power per pound of fuel as a fusion reaction.
Unfortunately, though it releases more power, this power is harder to
directly use to power the ship. It is however far more dangerous to
handle. If we could synthesize the thousands of tons of antimatter this
would take. It would have the potential of exploding with a force of
hundreds of millions of H-bombs.
We do not have the technology needed to synthesis, store, or ship
anti-matter on this scale, and are not likely to get it by 2050.
Ramscoop
This idea would allow a ship to scoop up interstellar hydrogen and use it
for fuel. Like a fuel launcher system it could accelerate to high speeds
without concern for high fuel to weight ratio's.
Unfortunately we don't really know what's in interstellar space, but we do
know we are in a very thin part of it due to a recent supernova in the
area. We might need a scoop thousands of kilometers across for a decent
sized ship.
We also know that straight hydrogen is very hard to fuse, and doesn't fuse
as quickly as we might need.
All in all we have no real idea on how to make such a ship work.
Future tech
The engineering and science we have now and assume we will have in the
future will change. Fusion, fission, relativity, quantum mechanics, and a
host of other basics of current physics; all were discovered within the
last hundred years. We can conservatively expect physics to have changed
far more in the next hundred years, then it did in the last hundred years.
What technologies that age will have on hand are impossible to guess. They
could have matter conversion, hyperlight drives, new understandings of
inertia and kinetic energy, or all those and far more. Any of these would
dramatically effect our ability to travel between the stars. So even
though we can't come up with any practical ideas for exploring the stars
now, we can be sure our descendants will find it far easier than we
imagine.
Kelly Starks
----------------------------------------------------------------------
Kelly Starks Internet: kgstar@most.fw.hac.com
Sr. Systems Engineer
Magnavox Electronic Systems Company
(Magnavox URL: http://www.fw.hac.com/external.html)
----------------------------------------------------------------------