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From: Kelly St <KellySt@aol.com>
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Date: Thu, 11 Dec 1997 23:11:01 EST
Cc: starship-design@lists.uoregon.edu
Subject: Re:  Re: Re: Re: Re: starship-design: One way (again...)
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In a message dated 12/11/97 7:53:47 AM, kuo@bit.csc.lsu.edu wrote:

===>
>>True I was suggesting a service life goal for a 2 way ship at 40 years,
which
>>seems a streach, but probably doable.  But adding a few decades on the end
>>would significantly cut your odds.
>
>40 years?  You mean we're just going to go there and immediately
>come back?  Now _that_ sounds like a sad waste.

12 years to get there, 12 years to get back here, 8 year in systems survey,
resuply, and servicing time, 8 year reserve capacity.


>But then again, you are also assuming twice the delta-v capability,
>which could blow up the fuel costs a thousandfold or more.

It came out to a 400 to 1 fuel ratio.  About $40 billion worth of Lithium-6 at
current market rates.


===>
>>Actually since you need all engines working to brake you into
>>the system, but can take as long as you like to burn you way
>>back up to speed on the way back, the return boost can afford
>>for most of the engines to fail or be dumped.
>
>Huh?  It's symmetric.  You can afford many of your braking engines
>to fail during "storage"--you just need to start your deceleration
>run earlier.  Naturally, you will start the run early enough so
>that you have room to spare in case some engines fail during the
>braking run.

You won't know if they've died on the shelf until you test them and fire them
up.  In any even I was more worried about burn outs during operation.  You
presumably have enough reserve thrust to throatle up the other engines to
compensate.  But if you lose to much thrust you'll over shoot.


>For the return journey, OTOH, you can't just take as long as you
>like.  You need to get back before your supplies run out, and
>losing most of your engines could result in extending your
>acceleration run several decades, assuming you somehow (how?)
>refuel in system.

The accel run is only a year or two even for the fuel/sail.  Loseing half you
engines isn't likely to over run your 8 year mission pad.


>If you're not refueling in system, then you can afford only a
>few rockets remaining for your return acceleration because of
>the greatly reduced mass relaxing thrust requirements.
>
>If you are refueling in system in a fuel/sail like starship,
>then the mass during the deceleration run and the return
>acceleration run are equivalent.  Losses in rockets in either
>leg have the same effect on extending the mission time.
>
>If you are refueling in system in a pure rocket starship, then
>you can ill afford much loss in rockets because of the greatly
>_increased_ mass compared to during the deceleration run.
>
>Engine failures for the deceleration and return acceleration runs
>will both extend the mission time.

Extending the mission time isn't a big problem.  Over shooting the system by
light weeks could be.


>>>2. Oxygen recycling and CO2 scrubbers.  At least with current
>>>   technology, they have a limited expected life span, but
>>>   they are relatively lightwieght so many spares can be
>>>   carried.  I'm not sure about their shelf life.
>
>>Scrubbers wouldn't work, but we could synthasis the ox out of water in the
>>air.  (Odd bit of matabolism I found.  The ox we breathing winds up in the
>>water we excreat, the ox in the CO2 comes from other sources.  weird.)
>
>Not really.  That's the way respiration works.
>
>>>3. Water recycling.  I'm not sure about this part.
>
>>Boil it to steam and condese it out.  Replace burned out reaction chambers
>>every few years(?).  Foutunately stainless steel is plantifull in asteroids.
>
>Stainless steel isn't plentiful anywhere except maybe landfills.  It
>has to be refined.  This is something where spares will have to be
>brought, but these spares should last practically forever in
>storage.

It is plentiful in asteroids.  I.E. nickel iron asteroids.  The metal ores
rich enough to use with little processing.  Not the best grade, but
acceptable.


>>>4. Food storage.  Irradiated canned food will easily last a couple
>>>   hundred years.
>
>>The containers arn't likely to last for centuries!
>
>In low pressure storage hermetically sealed in inert gas?  I don't
>see why not.

Theyll corrode with the chemicals in the food.


===>>
>>>>>Why would the crew be wearing out?  We'd be getting old after a
>>>>>while, but at that point it would be getting less and less
>>>>>important to have the equipment last much longer.
>
>>>>It has to keep working for the crew to keep living.  If it
>>>>needs repair NOW, you can't just hope it woun't fail for
>>>>a decade or two for the last crewman to die.  It almost
>>>>certainly will fail in months to years.
>
>>>Why would it almost certainly fail in months or years?  Exactly
>>>what mission critical components are certain to fail, even with
>>>triple redundancy?  (If there's only one or two crew left,
>>>the life support systems will be well below capacity.)
>
>>How many months with out service would you expect your car to keep runing
>>after the check engine light comes on?
>
>Not too long, but if I have 5 cars I can live with one of them
>breaking down.  Remember, we're talking about the last one or two
>survivors living in a habitat designed for at least a dozen.
>That leaves a lot of room for redundancy.

However a life support system built to supply hudreds might have serious
troubles running only for two or three.


>>Why do you think ship and subs keep
>>such large maintenece crews, and airplaces often need days of support crew
>>time for every hour they fly.  This stuff takes a beating.  And if any of
the
>>parts cut out, the system starts to fail.
>
>Yes, that stuff takes a beating.  They're combat machines that have
>to directly compete with their own kind.  This starship isn't some
>combat machine, and it's going to take things nice and slow.

At .4c?  We obviousl have different ideas of slow.  ;)


===>>


>>>>Your sending people out to to a decade or two of work (at most until the
>>>>exploration gear become unservicable) and then sit in the deralic ship
until
>>>>they die.  
>
>>>Why would the exploration gear become unservicable so quickly?
>>>At the very least, we can expect handheld optical telescopes
>>>to last hundreds of years.  Even that alone, at such a close
>>>range, is enough to do serious scientific observations impossible
>>>from the Solar System.  (Even if we figured out a way to make
>>>astronomically huge optical telescopes able to equal their
>>>resolution, we could not make fine corona observations since
>>>we'd lack the ability to shade out the photosphere.)
>
>>Actually telescopes arn't worth sending, you can see the systems perfectly
>>well from here with a big enough scope.  FAR easier to build a scope here
with
>>a synthetic apiture a few light secounds across, rather then keep a 1 meter
>>scope working a few light years from home.
>
>You won't be able to easily shade the photosphere.

We have as far back as skylab, can't see why we would forget by 2050.

>>Yes you can shade out the photosphere from here, especially from space.
>
>With your "synthetic aperture" telescope, you'd need a shade at least
>the size of your synthetic aperture and it would have to be placed
>in interstellar space between the target star and your telescope
>system (it has to appear the same size as the target star).

Or a separte small shade in each scope.


>>Or, you could use electronic imaging systems that can see the corona
>>without blocking the photosphere.
>
>Doesn't work with LBI.

Why?  

>>No observation studies (assuming you can keep the scopes working without
>>needing to strip their aiming and stabalization systems, or cooling, or the
>>rest), arn't going to cut it.  You have to get direct data from drop probes
or
>>samples, preferable bringing some samples home where the better lab gear is.
>
>Samples?  Samples of what?  Sure, there _might_ be planetoids around
>Alpha Centauri.  But those can be visited directly with the ship,
>if need be.  Big planets with significant gravitational fields would
>present a problem, but there's no reason for us to currently expect
>any such things orbiting there.  Binary star systems don't make for
>too many stable orbits.

Binaries can have stable orbits, thou they have to be much greater, or smaller
then the distence between the stars.  (3 star in the Centauri system as I
remember.)

Besides if theirs isn't any planets to speak of, theirs no reason to go.  You
can study the star nearly as well from here, and the difference isn't worth
sending a ship for.


>>>>Thats effectivly a suicide mission.  I know a few folks in this group
>>>>disagree, or don't care, but it still would meen no government on earth
>>could
>>>>get permision for such a mission.  I.E. your throwing away a crew for no
>>>>critical reason.  Specifically your doing it to save money, which is
really
>>>>not going to sell.
>
>>>By your logic, life is a suicide mission.  No matter what, you're
>>>going to die somewhere.
>
>>>Honestly, if I and others like me were sent on a _2_ way mission, We'd
>>>be more than halfway tempted to disobey orders and simply stay.
>
>>>That aside, the crew isn't thrown away.  They're simply taking the
>>>"retirement plan" of their choice.
>
>>How many ships crew, deside to beach their ship and hope they die before it
>>does?
>
>How is this question relevant?  No oceangoing ship ever built is even
>remotely like the starships we're discussing.

Because that your senerop.  Go to the system.  Do you mission for a few years
until the gear burns out.  Then hole up in the deralict ship for the rest of
your life.


>>Or how many arctic explorers would agree to go knowing they'ld live out
>>their days in those cramped tents or shacks in the ice.  Nothing to do but
try
>>to stay alive a few days longer.
>
>The arctic is frankly a pretty boring place.  Alpha Centauri is pretty
>exciting place.

How?  You don't even expect their to be any planets or much asteroids to look
at?  the Arctic would be comparativly busy and comfortable.

>>>Anyway, doing something to save money has long been a strong selling
>>>point.  That's why Mars pathfinder is this tiny little cart which
>>>can't even send data up to orbit rather than the originally
>>>envisionned self-sufficient rovers bristling with sensors.  It's
>>>why Magellan has only the rather limited radar rather than radar,
>>>IR, and optical, and it's why they trashed it into Venus's
>>>atmosphere when it could have continued operating it for years.
>
>>People don't mind you using expendable equipment and abandoning it when your
>>done, but they get very upset when you do the same to personel.
>
>These people aren't being abandonned.

They are sent to do a mission, then left their to die when the mission is
finished.  That sounds like abandonment by my dictionary.


===>>>
>>Also you might note my Explorer system has over a .3 c cruse speed, and the
>>fuel sail has over a .4c cruse speed.  .1 or .2c speeds would require flight
>>times of 20-50 years each way.  Totally unfeasable.
>
>A 20 year 1-way trip is what we're discussing.  The tacit assumption
>is that a faster cruise speed is unavailable.  Assuming a straight
>fusion rocket like a highly refined MagOrion, a delta-v limit of
>..4c (which implies a cruise speed of .1c) is rather reasonable.
>This assumes the fusion rocket comes within an order of magnitude
>of the theoretical maximum.

Whos we?  I never heard you mentioned this assumption, or specify such a ship,
and I've repeatedly  refured to the fuel ratios and speed capacities of the
fuel sail.


>Honestly, I'd be half tempted to go on a .1c 1-way trip (40 years).
>I picked .2c since it was fast enough so that I would _jump_ at
>the opportunity to go.

Given the slow speed, you'ld push the service life of systems, which would
demand a bigger heavier ship to allow the added service life.  It would be
cheaper to just up your fuel mass ratio, and get their quicker.  Also with a
40 year flight virtually all your crew would be in their 70's and 80's, and be
40 years out of practice and behind the times.


>>>>Past
>>>>that your need to strip those systems for pars to regulate life support,
>>>>medical, etc..
>
>>>Huh?  Keeping the systems alive will be a matter of repairing them
>>>with spares.  There's not much commonality between a CO2 scrubber
>>>and an IR camera.
>
>>The IR cameras cryo cooler, aiming motors, and electronics could be used in
>>everything from food processors to refrigeration systems, the images might
be
>>needed for medical, etc..
>
>It's theoretically possible to share those components, but entirely
>impractical once you look at the differences between the systems.
>A cryogenic cooler designed to cool a small space to 5 degrees K
>isn't going to be much like a refrigerator designed to cool a large
>space to 5 degrees Fahrenheit.  The micrometer stepping motors for
>slowly slewing a camera with minimum vibration are radically
>different from a brushless DC motor designed to run an air pump.
>About the only common electronics components would be assorted
>resistors, capacitors, and microcontrollers, but you're going to
>have thousands of these in storage.  The camera itself is designed
>for focus at infinity, which is very different from anything you'd
>want for medical imaging...

The lens would be different, the imagining chipcould be the same.  In general
to keep the spare parts count don't everything would be designedto use the
same standard parts.  Cryo coolers for long term storage to low thermal
imaging.  Motors for..etc..

>>>Most of the time spent on a manned spaceship, at least currently, is
>>>keeping yourself alive.  That's a given.  But really that's not so
>>>different from life here on Earth (especially if you're a farmer).
>
>>Very little of the time spent in current life is related to survival.
>>Probably less then 1/5-1/20th (depending on how you figure it).
>
>Most people work at least 40 hours a week, and spend maybe 8 hours
>a week just eating.  Not counting 8 hours a day for sleeping (which,
>if anything, counts towards time used up surviving), that's 43% of
>the time.

And if you assume you grocery bill is $80 per week, Rent and utilities $150
per week.  $15- $20 and hour pre tax/benifits ave salery.  You work about 12 -
15 hours a week for survival.

>If you're a farmer, then you probably spend a lot more time working.
>
>>The scientists on the crew would be there to do science and
>>support personel would keep the ship runing.
>
>At least for the cruise leg, everyone on board would be there to
>keep the ship running, but it should be easy going early on.  At
>the target system, everyone on board should be there to "do
>science".  Even someone completely unfamiliar with astronomy
>at the beginning of the mission could learn as much about
>astronomy as any PhD in 20 years.

The ship will need about as much servicing on the cruse as anywhere, the
mission systems (shuttles, probes, minning systems, etc..) will need a lot
more.  So the support crew to do all that would need to grosely outweigh the
scientists or landing survey crews.  The latter would need to be separte folks
or they would never have any time to do research work.

>>But as the ship deteriorated it would require
>>exponential growth in sevicing, and the science gear, crew, and
>>systems would be droped, or canabalized to service the rest.
>
>As I stated before, the ship would be maintained with replacement
>parts, rather than canabalizing components.
>-- 
>    _____     Isaac Kuo

Kelly