Author Topic: Jim's "Mythbusters" thread: ISS Lesson Learned - Modules should Skylab Sized  (Read 19059 times)

Offline manboy

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All design work at the time that had been done on ST Freedom would have had to been scrapped

Big problem: ESA and JAXA had been "locked" into the program from the mid-80's. With their Colombus and Kibo modules.
That's also the reason why Freedom / Alpha / ISS was never cancelled: don't anger the international partners !
That doesn't mean that other modules wouldn't have been worked into the plan. And if it was desired than both the Columbus and Kibo modules could have been launched at the same time.
"Cheese has been sent into space before. But the same cheese has never been sent into space twice." - StephenB

Offline simonth

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A rather good "myth" buster for this one. As Jim says, the most important lesson learned from the ISS program is "don't bank on an extremely expensive vehicle with potential long standdowns without alternative options for delivery".

No matter who the next space station's developer and operator will be, we can be pretty certain the individual pieces will not be much heavier than the current ISS modules.

Another thing both Mir and ISS taught is that commonality can pay off and that the Russian approach of docking spacecrafts and modules (each one has its own RCS and attitude control system) is by far easier and cheaper than the "robotic arm does it with many EVAs and a big truss with big solar arrays" approach.
« Last Edit: 06/19/2010 06:46 PM by simonth »

Online Robotbeat

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A rather good "myth" buster for this one. As Jim says, the most important lesson learned from the ISS program is "don't bank on an extremely expensive vehicle with potential long standdowns without alternative options for delivery".

No matter who the next space station's developer and operator will be, we can be pretty certain the individual pieces will not be much heavier than the current ISS modules.

Another thing both Mir and ISS taught is that commonality can pay off and that the Russian approach of docking spacecrafts and modules (each one has its own RCS and attitude control system) is by far easier and cheaper than the "robotic arm does it with many EVAs and a big truss with big solar arrays" approach.
I wonder if the overhead for EVAs can be reduced SIGNIFICANTLY while maintaining safety? You don't usually have two dozen people following around SCUBA divers, do you? I know some SCUBA divers who like to go completely solo.
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Offline SpacexULA

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SIGNIFICANTLY while maintaining safety? You don't usually have two dozen people following around SCUBA divers, do you? I know some SCUBA divers who like to go completely solo.

Hopefully Robonaut helps reduce the hours needed for for EVA.  Makes me wonder how much of the Assembly could have been completed with 0 EVA hours if Robonaut had existed 10 years ago.

When doing underwater oil work, 2 operators is the absolute minimum you will see underwater together.  Some jobs require up to 6 people to be suited up at a time, with only 1-2 person crew working.  The others are there for breaks and backup.
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Online Robotbeat

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SIGNIFICANTLY while maintaining safety? You don't usually have two dozen people following around SCUBA divers, do you? I know some SCUBA divers who like to go completely solo.

Hopefully Robonaut helps reduce the hours needed for for EVA.  Makes me wonder how much of the Assembly could have been completed with 0 EVA hours if Robonaut had existed 10 years ago.

When doing underwater oil work, 2 operators is the absolute minimum you will see underwater together.  Some jobs require up to 6 people to be suited up at a time, with only 1-2 person crew working.  The others are there for breaks and backup.
I was mostly speaking about those on the ground.
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To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline JohnFornaro

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modifying the construction program so you don't need a particular vehicle present...

Absolutely agree.  One of  the other benefits is that if there is a module specification, then several manufacturers can make modules, and it can be reasonably expected that they will fit together.  By this method, the manufacturing base could be enlarged, and manufacturing costs can start reducing.

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Volume is not as important as mass, in the end mass determines what you can do. whether you're talking about a space station or a colony.

Yes, but that's not quite the comparison I was making.  With volume, you get mass for free, so to speak.  I've been thinking about the idea that "mass is your friend".   Obviously, launch costs are your enemy, so this snappy meme will be a hard sell, but we need more mass in space in order to build anything of any size.

The estimate of "assembly intensive" costs is part of this debate, I agree.  The way I'm looking at it is thatfirst, I'm trying to identify those aspects of space station construction which are independent of scale.  Back to one of my favorites; whether the modules are large or small, standardization saves costs by extending the amortization period.  Whether large or small, for the foreseeable future, some EVA activity will be involved in their assembly.  Whether large or small, time and money will be needed for either approach.

Then, I would start thinking about those issues which differ between large and small modules.  Obviously, how the pieces get up there is pertinent.  If we already have infrastructure, vehicles, and abilities for launching small modules, then we need to consider developing these things for the large modules.  These don't exist today, and won't for years, and many dollars.

So today, it seems that smaller modules are the way to go, which doesn't appeal to the BFR crowd who insist that over the long run, larger modules have a lower unit cost.  That may be readily granted in the discussion, but consider the time for implementation, and their argument fails.

We can get a space station made of smaller modules up there faster.  Time is of the essence.  Presupposing that the prospecting has been done, we cannot create wealth in space without people up there.  The BRF proposals delay this while adding the cost of development and discarding the capital assets that are already on the ground.

An imperfect analogy is my recent front end loader tractor purchase.  A new four wheel drive sub-copact tractor with a front end loader would have cost $17K and a healthy monthly payment for five years or so.  A second hand, 15 year old two wheel drive tractor cost $3K -- what I had in the bank.  Many's the time I wished I had the better tractor.  I've broken the steering linkage, and have gotten stuck several times.  But I'm getting all the work done that I need to get done, and in this economic time, I don't have a monthly payment.

[Edit 06-21-10  The new tractor analogy is even better!  For another $6K, I could get a backhoe; $3K a chipper; etc.  The three point hitch allows many useful attachments.  Over the long run, it is the better buy, just like the HLV.  Just wish Congress wifey would let me buy one.]

We need cheap lift more than we need heavy lift.

The exobiology question on Mars may change the prioritization of future missions.  It is incorrect to wait for that question to be settled before acting.  Plus, it would be incorrect to design that mission, other than with a broad brush, before the question is settled.  That next mission will need to be determined by a different procedure from the missions to dead worlds.
« Last Edit: 06/21/2010 01:41 PM by JohnFornaro »
Sometimes I just flat out don't get it.

Offline neilh

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So today, it seems that smaller modules are the way to go, which doesn't appeal to the BFR crowd who insist that over the long run, larger modules have a lower unit cost.  That may be readily granted in the discussion, but consider the time for implementation, and their argument fails.

Are there actually any figures on how unit cost compared between Skylab and Mir? For that matter, are there any reliable figures on what the total cost of constructing Mir was? The rough estimates I've found on the internet range between $3B and $4.3B, presumably given in 1980s US dollars.
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Offline manboy

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So today, it seems that smaller modules are the way to go, which doesn't appeal to the BFR crowd who insist that over the long run, larger modules have a lower unit cost.  That may be readily granted in the discussion, but consider the time for implementation, and their argument fails.

Are there actually any figures on how unit cost compared between Skylab and Mir? For that matter, are there any reliable figures on what the total cost of constructing Mir was? The rough estimates I've found on the internet range between $3B and $4.3B, presumably given in 1980s US dollars.
Russian engineers get paid a lot less than American ones so a Mir to Skylab comparison might not be the best.
"Cheese has been sent into space before. But the same cheese has never been sent into space twice." - StephenB

Offline A_M_Swallow

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Russian engineers get paid a lot less than American ones so a Mir to Skylab comparison might not be the best.

A simple way of handling inflation and differing pay rates is to produce an estimate in man hours.  Converting man hours to this years money is a simple multiplication.

Offline manboy

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We need cheap lift more than we need heavy lift.
As of 2010 "cheap lift" really seems like a pipe dream. And it has been a pipe dream that has been shoved down our throats for almost forty years when were sold the Shuttle.
"Cheese has been sent into space before. But the same cheese has never been sent into space twice." - StephenB

Offline mmeijeri

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As of 2010 "cheap lift" really seems like a pipe dream. And it has been a pipe dream that has been shoved down our throats for almost forty years when were sold the Shuttle.

Sure, as a big government-run development program trying to build a large RLV. But a government that simply does exploration and launches all its propellant to a depot (or refuelable spacecraft) on freely competing launchers could lead the market to develop small RLVs. And we need not assume RLVs are the answer, it could also be cheap mass produced expendables or some hybrid of the two. Or maybe even something really exotic like tethers or beamed power propulsion.

And exploration could start with existing launchers, so we wouldn't have to wait for the cheap lift to emerge first. In the worst case it will be no more expensive than a dedicated HLV, it will probably lead to at least some reduction in commercial launch prices, and in the best case it will lead to cheap lift and commercial development of space in our lifetime. We have all the technologies that are needed to get started. All we need is a spacecraft.
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Offline JohnFornaro

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And exploration could start with existing launchers, so we wouldn't have to wait for the cheap lift to emerge first. In the worst case it will be no more expensive than a dedicated HLV...

Not only that, in the worst case, it could start happening tomorrow, or pretty darn soon.  Fire up a half empty cannister of fuel to LEO.  Demonstration mission accomplished!

Time is of the essence, then cost.
Sometimes I just flat out don't get it.

Offline mmeijeri

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Demonstration mission accomplished!

It gets better, the demonstration mission was first accomplished more than thirty years ago and is repeated a couple of times each year. It's called Soyuz/ATV.

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Time is of the essence, then cost.

Both are equally important I think. There simply isn't going to be a lot of money soon. What I'd like to see is copious amounts of propellant being launched as soon as possible, so private work on cheap lift can begin as soon as possible. The New Space people are already starting to get into suborbit just about now and Old Space could start work on cheaper orbital (R)LVs immediately. We'd have to find something useful and inspiring to do with that propellant. Given budget realities that something is probably going to have to be a lot less ambitious than landing people on the moon. The flip side is that it would reduce launch prices sooner.
« Last Edit: 06/22/2010 02:11 PM by mmeijeri »
We will be vic-toooooo-ri-ous!!!

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