[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: starship-design: BOUNCE starship-design@lists.uoregon.edu: Admin reques

I got a bounce message on this, so incase it never made it...

In a message dated 12/13/97 1:11:59 PM, you wrote:

>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,
>>>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
>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
>>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
>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
>>>>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
>>>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
>>>>>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
>>>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.
>>>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
>>>samples, preferable bringing some samples home where the better lab gear
>>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
>then the distence between the stars.  (3 star in the Centauri system as I
>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
>>>>>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
>>>>>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
>>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
>>>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
>>>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
>>>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
>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
>40 years out of practice and behind the times.
>>>>>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
>>>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
>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