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Space Forum / Space Flight / September 2005Pressure-feed without heavy tanks?
Hello, I'm wondering if anybody considered a pressure-feed system with big and light low-pressure tank to store fuel, and very small, strong tank to feed combustion chamber. First, the fuel from low pressure tank is decanted to small tank. Next, small tank is pressurized. Fuel from this tank feeds combustion chamber. When this tank is empty, the cycle is repeated (refueling -> pressurizing -> feeding). If there are two high-pressure tanks instead of one (for each component), it is possible to feed combuston chamber continuosly. Is there a point in it?  SignatureBorys Dabrowski Am Mon, 19 Sep 2005 12:19:05 +0200 schrieb "Borys Dabrowski": >I'm wondering if anybody considered a pressure-feed system with big and >light low-pressure tank to store fuel, and very small, strong tank to feed [quoted text clipped - 4 lines] >tanks instead of one (for each component), it is possible to feed >combuston chamber continuosly. Is there a point in it? Nearly every engineer who has to do with production design will tell you, that whenever it is possible to replace batch production by continuous flow production, it will nearly everytimes be decided to do so. And that is not only because continuous flow is more productive than batch - it tends to be less complex and less error-prone, too. Just one-time costs (development and initial procurement of productive means) of batch production may be less, but long-term costs favor the continuous flow. Please see the analogons for rocket propulsion - a turbopump assembly may be more expensive than this dual/triple tank constuction you mention, but I guess, it is much less failure sensitive... cu, ZiLi aka HKZL (Heinrich Zinndorf-Linker) Signature"Abusus non tollit usum" - Latin: Abuse is no argument against proper use. mailto: heinrich@zili.de http://zili.de > Hello, > I'm wondering if anybody considered a pressure-feed system with big and [quoted text clipped - 5 lines] > tanks instead of one (for each component), it is possible to feed > combuston chamber continuosly. Is there a point in it? Search for Flometrics. There is an operating system as you describe. >Hello, >I'm wondering if anybody considered a pressure-feed system with big and [quoted text clipped - 5 lines] >tanks instead of one (for each component), it is possible to feed >combuston chamber continuosly. Is there a point in it? Possibly, and it's a clever idea. However, a company called Flometrics beat you to it, and has been testing experimental hardware along those lines for the past couple of years. <http://www.flometrics.com/rockets/rocket_pump/rocketpump.htm> Signature*John Schilling * "Anything worth doing, * *Member:AIAA,NRA,ACLU,SAS,LP * is worth doing for money" * *Chief Scientist & General Partner * -13th Rule of Acquisition * *White Elephant Research, LLC * "There is no substitute * *schillin@spock.usc.edu * for success" * *661-718-0955 or 661-275-6795 * -58th Rule of Acquisition * [...] > Possibly, and it's a clever idea. > > However, a company called Flometrics beat you to it, Damn, again? The same was with the wheel. Thanks to all for the answers. SignatureBorys Dabrowski >...First, the fuel from low pressure tank is decanted to >small tank. Next, small tank is pressurized. Fuel from this tank feeds >combustion chamber. When this tank is empty, the cycle is repeated... You've reinvented what's called a "pistonless pump". The basic idea has been around for centuries. It's attracted some interest for rockets lately; Flometrics <www.flometrics.com> in particular is pursuing it. It uses the same amount of pressurizing gas as a pressure-fed system, but the main tanks are considerably lighter, and the pressurant is gradually dumped overboard (by venting from the pump chambers) during operation rather than being retained until the end. Depending on assumptions, it may be mass-competitive with turbopumps, and development costs for any specific system look much lower. (Turbopump development is not easy.) Signaturespsystems.net is temporarily off the air; | Henry Spencer mail to henry at zoo.utoronto.ca instead. | henry@spsystems.net Depending on assumptions, it > may be mass-competitive with turbopumps, and development costs for any > specific system look much lower. (Turbopump development is not easy.) Part of it not being easy is the approach. There might be ways around standard practice that change this. One thing is to design the engine as a system instead of several systems. Hope to have proof in a few months. If I do, I'm getting a shirt made for you to sign. [pistonless pump] > It uses the same amount of pressurizing gas as a pressure-fed > system, but the main tanks are considerably lighter, and the [quoted text clipped - 4 lines] > any specific system look much lower. (Turbopump development > is not easy.) So, there is working and cheap solution, used in several small rockets - and that is all. It only proves, how conservative and noninnovative the 'rocket businnes' is. PS. My earlier responses didn't reach a group, so thanks to all for the answers again. SignatureBorys Dabrowski henry@spsystems.net (Henry Spencer) wrote: >(Turbopump development is not easy.) There's an Nth-hand and quite possibly apocryphal story I heard in the 1970s from a contact at Pratt & Whitney, who'd heard it from a German at Huntsville. Supposedly, when it was decided the follow-on to the A-3 would have a turbopump, Thiel had an assistant canvass all the German firms judged capable of making a suitable pump, "feeling out" the state of the art without any mention of rockets: "Just out of curiosity, would be possible to attain flow rate X with a pump weighing no more than Y..?" The assistant came back and told Thiel that every one he asked had boggled and said "WIE schnell?! WIE klein!?" [HOW fast?! HOW small?!] And for weeks afterward, whenever Thiel and von Braun ran into each other, they would chant in unison "WIE schnell?!? WIE klein??!?" and laugh like maniacs... yes, flowmetrics has http://www.flometrics.com/rockets/rocket_pump/rocketpump.htm |
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