Author Topic: Waiting for Zefram Cochrane  (Read 7026 times)

Offline sdsds

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Waiting for Zefram Cochrane
« on: 08/18/2010 07:21 am »
In the Star Trek universe, Zefram Cochrane demonstrates warp drive technology in 2063.  What's the point of developing any other spaceflight technology between now and then?  Why not just wait for Zefram?

Obviously this is meant metaphorically.  On a much more concrete level equivalent questions might be, "What's the point of developing hypergolic depots when they're just going to be made obsolete by cryogenic depots?"  Or, "What's the point of developing rocket launch technology when we could just wait for space elevators?"  And so on.

How do we know when to invest in intermediate technologies; technologies we hope will one day be obsolete?  More pertinent to my current situation here, how do we convincingly make the case for developing an intermediate technology?
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Offline KelvinZero

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Re: Waiting for Zefram Cochrane
« Reply #1 on: 08/18/2010 09:21 am »
I think I have often met this "Waiting for Zefram Cochrane" attitude and it is quite a worry. I sometimes suspect it actually is a legacy of Star-trek. If it inspires you to get into really difficult esoteric physics then great.. but I'm sure you people have all met examples of posters calling NASA idiots for not developing real spaceships ...like they see on TV.

As for hypergolic depots.. I haven't thought about it. I imagine if this were something to bring humans home from the Moon after a 6 month stay then you might want something really reliable like that.

No one is building a moon lander though so we have time.

My (unresearched) opinion was that the most immediate use of a propellant depot would be to make a depot out of an existing second stage, in order to top up an existing second stage for an EDS stage to increase the size of robotic missions beyond earth orbit. This implies H/LOX.

Does the sort of hypergolic engine that could benefit from a propellant depot exist yet?

Offline Warren Platts

Re: Waiting for Zefram Cochrane
« Reply #2 on: 08/18/2010 01:16 pm »
Warp drive as a metaphor for cryogenic propellant depots isn't very apropos for at least two reasons: (1) warp drive violates the laws of physics--crygenic depots do not; (2) cryogenic depots will not be developed several decades into the future--they are being developed right now. Probably, the first practical demo will fly as soon as 2015. Much work on storing and transferring cryogenic propellants has already been done, on Earth and in orbit. All that's left is putting all the ingredients together.

Since cryogenic depots are the current state of the art, hypergolic depots aren't an intermediate technology--they are already obsolete by definition. To count as an intermediate technology, the item must be a useful bridge to the technology to be developed in the future. If the desired, optimal technology is being developed in the present time, there is no need for the bridge. At that point, the "intermediate" technology is a needless, suboptimal duplication of capability, and therefore a counterproductive waste of resources that actually delays, rather than speeds up, the development of the desired technology.
"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return."--Leonardo Da Vinci

Offline khallow

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Re: Waiting for Zefram Cochrane
« Reply #3 on: 08/19/2010 12:10 am »

Obviously this is meant metaphorically.  On a much more concrete level equivalent questions might be, "What's the point of developing hypergolic depots when they're just going to be made obsolete by cryogenic depots?"  Or, "What's the point of developing rocket launch technology when we could just wait for space elevators?"  And so on.

There are two rebuttals. First, every technology we have developed is on track to be obsoleted. Why did we bother to develop them when we knew something better would come around? Answer: because future obsolescence is not a good measure of the value of a technology. Usually, it's better to go now with what you have rather than wait for something better. In a military analogy, you fight with the army you got not the army you wish you had.

Second, when do we stop waiting? Which future magic technology is worth developing then and there, rather than waiting for an even more magical technology further back on the horizon? We have to stop waiting at some point or we'll never do anything.
Karl Hallowell

Offline khallow

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Re: Waiting for Zefram Cochrane
« Reply #4 on: 08/19/2010 12:24 am »
As to the linked discussion, I think the view there is that a cryo propellant depot isn't much more complex than a hypergolic propellant depot. So you don't gain much by running a demo that uses hypergolics over cryo.

My view is that it depends on the application. In particular, a propellant depot that will be untended for a considerable length of time in a similar heat environment to Earth orbit (or which fuels spacecraft that will hold propellant unused for a long period of time), favors hypergolics or other low boil-off propellants. While a cryo depot is probably similar in complexity to a hypergolic depot, a (near) zero boil-off cryo depot is significantly more complex.
Karl Hallowell

Offline sdsds

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Re: Waiting for Zefram Cochrane
« Reply #5 on: 08/19/2010 12:57 am »
because future obsolescence is not a good measure of the value of a technology.

Ah yes!  Thank you for this response.  Somehow I was forgetting the concept economists call the present value of a future good.  To quote Murray Rothbard, "The investment decision will be determined by which is greater: the present value of the future good or the present value of present goods forgone."
(http://books.google.com/books?id=YGi5EbO32hgC&pg=PA63)

I think I have often met this "Waiting for Zefram Cochrane" attitude and it is quite a worry. I sometimes suspect it actually is a legacy of Star-trek.

Yes, that does really seem to be a part of it!  Another part is that NASA has had some pretty spectacular successes, and the population at large seems to have pretty high expectations of future success!

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Does the sort of hypergolic engine that could benefit from a propellant depot exist yet?

I suspect it does, but frankly I haven't proven that even to my own satisfaction yet!
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Offline mr. mark

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Re: Waiting for Zefram Cochrane
« Reply #6 on: 08/19/2010 01:16 am »
If i'm right, warp drive does not violate the laws of physics. Warp drive uses a static warp shell which isolates the vehicle from normal space time or something like that. Saw a special on the theory but, I really don't remember alot about it. Although to create a static warp shell would require a tremendous amount of power. Hey, don't take my word for it, better to ask Scotty I know he knows.
« Last Edit: 08/19/2010 01:17 am by mr. mark »

Offline pathfinder_01

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Re: Waiting for Zefram Cochrane
« Reply #7 on: 08/19/2010 02:30 am »
The biggest issue is that people don’t do technical demonstrations in orbit to retire risk and little gets done. This is why I was so gun ho about fy2011. 

Let’s say hydrogen or methane storage or does not work then you invest in hypergolic depots. 

However if you invest in hypergolic depots now, you have little reason to do so.  Higher performance upper stages use lox\loh. Both lox\loh and lox\methane are better ISP than hypergolic and we have no mission planed that can take advantage of hypergolic.  The lower performance means that instead of needing 51MT of lox\loh to push 21 tons (Orion) to l1, you now need about 70MT of hypergolic. This means increased costs.

In addition hypergolic are corrosive and toxic and they too are not without risk. There has been no transfer of hypergolic of the scale needed for exploration.  Basically you are banking that the risk of storage and transfer of cryogenics in space is greater than the risk of transfer of hypergolic. The system on the ISS isn’t suitable for the task of repeated fueling of a craft.  It could be used to refill the depot provided the amounts are small enough for instance progress only carries about 1MT of propellant but the depot might need to hold 20-100MT worth of propellant and the issues with hypergolic propellant isn’t boiling but protecting from freezing. This could require additional solar panels and batteries than a cryogenic one which means more mass and a more expensive rocket\refueling system.  The lower isp means you will need to refuel more often and the toxicity means increased handling costs.

Basically you have two roads. One seems shorter but has more traffic. The other is longer but has less. Until someone gets applicable data about which is the better route then neither route is the best. You need to choose one. I favor cryogenics because they would give more bang for the buck than hypergolic.

Offline Gregori

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Re: Waiting for Zefram Cochrane
« Reply #8 on: 08/19/2010 02:47 am »
If you wait for future magical technology, you very well may waste time that could have been used exploring with what you have. Technology has to be developed in steps until we get to something like the warp drive. If we don't try the technologies that seem plausible now, we won't learn lessons for future tech. The future technology you're hoping for may not work in reality.

Its disappointing that the tech we spend so much time developing will eventually obsolete.... but its all part of the process. Creating obsolescent technology is just a necessary evil. Doing with what can do now gets us there faster.


I'm sure the results from the Large Hadron Collider will point us in the right direction if we want to develop magical technology

Offline JohnFornaro

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Re: Waiting for Zefram Cochrane
« Reply #9 on: 08/19/2010 02:54 pm »
Or, what's the point of developing chariots if we could just wait for Chevy Novas?

And the same thing has been happening in our software industry:  Just wait till you see Windows XY!  Much better than Windows XX.  With politicians, it's slightly different:  Just wait til we get the bridge to nowhere complete.  You won't believe the economic prosperity that will follow!  The sociology department takes a slightly different approach:  We now know that juvenile delinquency is caused by broken families, poverty, bad nutrition, and poor education.  This new program will both redifine marriage and make divorce easier to get, will increase handouts by a certain amount, will rename the food pyramid to the food triangle and change the portions from ounces to servings, and enact new union laws that will ensure that all teachers, not just the good ones, have lifetime employement.  The legal department?  Existing law is incredibly complicated.  Let's simplify it by adding more complicated conditions.

[Takes deep breath.]

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Usually, it's better to go now with what you have rather than wait for something better.
Pretty much agree, which touches on the "tired" argument of extending the shuttle for five or six flights.

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In a military analogy, you fight with the army you got not the army you wish you had.
True, when you are attacked first.  Rumsfield's use of this logic was fatally flawed, because we elected to start that war before adequately preparing to do so.  But I digress.

Rothbard's quote up there is good: "The investment decision will be determined by which is greater: the present value of the future good or the present value of present goods forgone."

The difficulties that I see in the HSF and HLV discussions are that the values are imperfectly presented, often deliberately so by actually ignoring contrary values; and that politics overrules reason.
Sometimes I just flat out don't get it.

Offline 93143

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Re: Waiting for Zefram Cochrane
« Reply #10 on: 08/19/2010 05:25 pm »
Sometimes it seems to me that people advocate "waiting" for future technology because they subconsciously think technology advances on its own.

If we don't develop technology, it doesn't get developed.  It's not a question of whether or not X technology will be obsolete once Y arrives, and whether it's worth it to develop X in the meantime.  If we just "wait", we will get neither X nor Y.

Now, the question of hypergolic vs. cryogenic is a bit different, since they're both reasonably well understood, and we can start on either (or both) right now...

Offline JohnFornaro

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Re: Waiting for Zefram Cochrane
« Reply #11 on: 08/19/2010 06:54 pm »
Quote
...they subconsciously think technology advances on its own.
All those drugs have addled their brains.  You know, MSG, BHT, artificial sweeteners, wierdo anti-biotics in the cheeseburgers, melamine.  All that stuff. 
Sometimes I just flat out don't get it.

Offline kfsorensen

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Re: Waiting for Zefram Cochrane
« Reply #12 on: 08/19/2010 07:07 pm »
Sometimes it seems to me that people advocate "waiting" for future technology because they subconsciously think technology advances on its own.

Well said.  It's amazing how long it took me to grasp this incredibly simple concept.

Offline MP99

Re: Waiting for Zefram Cochrane
« Reply #13 on: 08/19/2010 08:56 pm »
Sometimes it seems to me that people advocate "waiting" for future technology because they subconsciously think technology advances on its own.

If we don't develop technology, it doesn't get developed.  It's not a question of whether or not X technology will be obsolete once Y arrives, and whether it's worth it to develop X in the meantime.  If we just "wait", we will get neither X nor Y.

I'd have thought that depends on whether the technology is being developed for non-space uses. The obvious example here being the downsizing of computer technology (which is surely now "small enough"), and the improvements in autonomous rovers & robotic technology.

One could also imagine GM being used to optimise plants for a greenhouse on the Moon or Mars (many years down the road).

However, for space usage, I'd have thought these would only fill the lower TRL levels.

With those few exceptions, your point is very well made. In general, I get the impression that basic, blue sky (ie government funded) research has suffered in comparison to commercially-biased, near-term research compared to where we were a couple of decades ago.

cheers, Martin

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