Angara News

Point out news stories, on the net or in mainstream media, related to polywell fusion.

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KitemanSA
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Re: Angara News

Postby KitemanSA » Thu Jan 01, 2015 3:04 am

93143 wrote:Mitigating the manufacturing costs doesn't get rid of all the other costs associated with launch vehicles, and all of those also scale with the size and number of stages. In fact, post-flight servicing/refurbishment is a whole new cost that expendables flat-out don't have, and it scales with size and number too, probably more than manufacturing cost does. So to first order, your scheme doesn't scale any better for reusable stages than it does for expendables.
Are you seriously equating manufacturing cost with reburbishment costs. Really?

Then consider that the reusability requires those stages to put out more impulse in order to do the same job, meaning either they have to be bigger or more numerous (= more expensive to have, use, and refurbish) or the Isp has to be better. Or both.
My example was more numerous, but also increased the payload.

In fact, your scheme would result in the main boosters and especially the core ending up much faster and further downrange by the time they had to drop off and go back, making the problem worse.
The zeroth stage booster would be easier to return to launch since they would run dry and get jettisoned much quicker. The pair of boosters would not be more difficult if it allowed an easier down range retrieval. Get high enough and you might just get a circumglobal retrieval for the core.

You can't just assume reusable = free and throw ganged cores at the problem. Or more sequential stages for that matter; each unique stage you add requires its own DDT&E and special manufacturing and handling treatment, which could rapidly eat up the advantage of reusability.
Nobody assumed "free", just cheaper. The fuel cross connect concept used by F9H in conjunction with fly back boosters may just make space flight affordable for common business.

hanelyp
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Joined: Fri Oct 26, 2007 8:50 pm

Re: Angara News

Postby hanelyp » Thu Jan 01, 2015 4:10 am

If you can't get the cost of recovery and refurbishment for your reusable stage to a small fraction of building a new expendable stage it doesn't work out. To get costs down the between launch inspection needs to approach plugging in to a diagnostics module and reading a report, or at most a technician taking a few minutes to verify that control systems respond. And typical refurbishment ideally being little more than flushing lines and refilling expendable fluids. Man hours to get the system back to flight condition are counterproductive to getting costs down.
The daylight is uncomfortably bright for eyes so long in the dark.

GIThruster
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Joined: Tue May 25, 2010 8:17 pm

Re: Angara News

Postby GIThruster » Fri Jan 02, 2015 3:03 pm

KitemanSA wrote:
93143 wrote:Mitigating the manufacturing costs doesn't get rid of all the other costs associated with launch vehicles, and all of those also scale with the size and number of stages. In fact, post-flight servicing/refurbishment is a whole new cost that expendables flat-out don't have, and it scales with size and number too, probably more than manufacturing cost does. So to first order, your scheme doesn't scale any better for reusable stages than it does for expendables.
Are you seriously equating manufacturing cost with reburbishment costs. Really?

Given none of us here have the numbers, I think he's wise to do so. Remember that the remanufacturing costs of Shuttle were what made it so vastly more expensive than any of the expendable alternatives. Musk is on his own to create the proper testing and remanufacturing of stages returned to Earth, but you can bet they'll be using all manner of Non-destructive Testing methods from eddy-current testing to ultrasound, and that stuff is not cheap. You're paying specialists just like we paid specialists to test and/or replace each of Shuttle's 26,000 tiles and rebuild her engines and turbo-pumps after every launch. Remanufacturing is expensive. The question of how expensive it will be for Grasshopper is not one we can answer, except that Must says he knows what he's doing and expects an order of magnitude decrease in costs. If he goes from $60M/shot to $6M, he gets to pocket $54M extra for every launch.

Personally I hope he's successful., but I would not assume those numbers are accurate.
"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis

KitemanSA
Posts: 6114
Joined: Sun Sep 28, 2008 3:05 pm
Location: OlyPen WA

Re: Angara News

Postby KitemanSA » Fri Jan 02, 2015 7:14 pm

GIThruster wrote:
KitemanSA wrote:Are you seriously equating manufacturing cost with reburbishment costs. Really?

Given none of us here have the numbers, I think he's wise to do so. Remember that the remanufacturing costs of Shuttle were what made it so vastly more expensive than any of the expendable alternatives.

As you point out, the SS SRMs were "remanufactured" and the VERY expensive refurbishment of the flying brickyard was still immensely less expensive than throwing it away and building a new one every time.
Somehow, I don't see Musk making a machine that costs as much to maintain and reuse as it does to make a new one. The numbers obviously make sense to him.

93143
Posts: 1131
Joined: Fri Oct 19, 2007 7:51 pm

Re: Angara News

Postby 93143 » Tue Jan 06, 2015 4:26 am

KitemanSA wrote:Are you seriously equating manufacturing cost with reburbishment costs. Really?

Of course not. Didn't you read my post?

Let me try this again: Higher Isp gives a larger proportional performance advantage to a reusable than it does to an expendable, for the simple reason that the stage performance and/or durability requirements are more extreme. No absolute cost comparison between reusable and expendable is suggested; however, it is noted that the costs associated with the reusable vehicle do scale with its size and complexity.

I suspect that weighting engine complexity at 100% and vehicle size and complexity at 0% is not the best way to arrive at an optimum design. Witness the BFR, which is shaping up into a single-stick vehicle using full-flow staged-combustion engines. From your most recent post I see you like to assume Musk knows what he's doing...


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