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Passenger market for suborbital flights.
On May 27, 9:27*am, Robert Clark wrote:
... the real problem is that the X-33 tanks are not of the usual cylindrical or spherical shape. Then we can get the minimal weight by using numerous small diameter cylindrical tubes to make up the shape of the conformal tanks without requiring the ultrahigh strength of the microscale fibers. Because of the large size of X-33 tanks we might even be able to have these cylindrical tubes be as large as say 10 centimeters across, and have them be of varying lengths so when bundled together they make up the conformal shape of the X-33 tanks. If they are 10 cm across and using the aluminum alloy, to be of the 1000 to 1 diameter to thickness ratio of the shuttle ET, they would have to have a 100 micron wall thickness. This is easy to achieve since for example common household aluminum foil may be only 16 microns thick: Reynolds Wrap* Aluminum Foil.http://vwrlabshop.com/reynolds-wrap-...oil/p/0014244/ Smaller diameter tubes if necessary would have a smaller wall thickness. Even tubes 1 cm wide requiring wall thickness of 10 microns is well within the range of commonly used aluminum sheeting. The effect of bundling the many tubes together would also give the complete tank strength as it would be be in the form of a honeycomb, a structure of inherently high strength to weight ratio. The viability of this idea would be easy test by using tubes made from common aluminum foil and testing how well they hold up to the pressures and temperatures seen in the cryogenic tanks. The tubes could be formed by epoxying the edges together and then epoxying the tubes together to form the shape of the conformal tanks. To form stronger tubes and bonds between the tubes we could also use a light brazing technique. The aluminum foil doesn't have the same strength to weight ratio of the aluminum alloys but it would serve to give a first level indication of how well the idea would work. At this first level you would probably also want to use liquid nitrogen rather than liquid hydrogen as well. Assuming the multitube method works to provide similar tank mass to propellant mass ratio as the shuttle ET, the bare mass of the X-33 liquid hydrogen tanks could be reduced from 12,000 lbs. to 6,000 lbs, and the liquid oxygen tank from 6,000 lbs. to 1,500 lbs, quite a large mass saving for a vehicle of bare mass of 65,000 lbs. For so many small cylindrical tanks, probably you would not want to have separate valves for each cylinder that all had to operate in unison. A couple of ways to release the fuel in a throttleable fashion might be to have each small cylinder be completely used up once it is opened, with a group of cylinders being opened sequentially, or to have one end of the cylinders be closed off and a single cap cover the other open end of all the cylinders which would be used to connect to a single valve for the tank. NASA does not seem to have much interest in funding further X-33 development. However, the U.S. Air Force is interested in developing a suborbital troop transport (which of course could also work as a commercial suborbital passenger transport): Pentagon seeks military role for space tourism technology. By Stephen Trimble DATE:23/02/09 SOURCE:Flight International http://www.flightglobal.com/articles...echnology.html Then considering the low cost nature of the idea, the Air Force might fund this since if viable it would lead to a suborbital transport in the X-33, and likely therefore also to a reusable single stage to orbit vehicle in the VentureStar. AFRL Seeks Reusable Booster X-Plane Ideas. Posted by Graham Warwick at 5/12/2009 2:36 PM CDT "Guy Norris alerted us to it a couple of weeks ago in Aviation Week, but the Air Force Research Laboratory has finally released its request for information on concepts for a reusable launch vehicle. They are calling it the Reusable Booster System (RBS), because the focus is on a fly-back first stage carrying an extendable upper stage. "The RFI's stated objective "is to identify potential operational RBS concepts, including a family of expendable stage variants, and feasible system development approaches." And it is a step towards a potential subscale X-plane demonstrator that could fly in 2017-18." http://www.aviationweek.com/aw/blogs...e-7a7a675f97de Reusable Booster Integrated Demo – Concept Options Maturation Study. (RBID-COMS) Solicitation Number: RFI-PKV-09-01 Agency: Department of the Air Force Office: Air Force Materiel Command Location: AFRL - Wright Research Site https://www.fbo.gov/index?s=opportun...&cck=1&au=&ck= This is for proposals for a reusable vertical launch, horizontal landing unmanned booster to serve as the first stage of a two-stage-to- orbit (TSTO) system. The description seems to be tailored made for the X-33 suborbital system. I'm inclined to think intentionally so. Then this might open up funding for alternative methods for obtaining lightweight tanks for the X-33 such as the multiple cylindrical tanks method. It also would make possible a suborbital troop carrier or commercial transport system. Bob Clark |
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Passenger market for suborbital flights.
On Jun 2, 2:56*pm, Robert Clark wrote:
... Pentagon seeks military role for space tourism technology. By Stephen Trimble DATE:23/02/09 SOURCE:Flight International http://www.flightglobal.com/articles...pentagon-seeks... *Then considering the low cost nature of the idea, the Air Force might fund this since if viable it would lead to a suborbital transport in the X-33, and likely therefore also to a reusable single stage to orbit vehicle in the VentureStar. AFRL Seeks Reusable Booster X-Plane Ideas. Posted by Graham Warwick at 5/12/2009 2:36 PM CDT "Guy Norris alerted us to it a couple of weeks ago in Aviation Week, but the Air Force Research Laboratory has finally released its request for information on concepts for a reusable launch vehicle. They are calling it the Reusable Booster System (RBS), because the focus is on a fly-back first stage carrying an extendable upper stage. "The RFI's stated objective "is to identify potential operational RBS concepts, including a family of expendable stage variants, and feasible system development approaches." And it is a step towards a potential subscale X-plane demonstrator that could fly in 2017-18."http://www.aviationweek.com/aw/blogs/defense/index.jsp?plckController... Reusable Booster Integrated Demo – Concept Options Maturation Study. (RBID-COMS) Solicitation Number: RFI-PKV-09-01 Agency: Department of the Air Force Office: Air Force Materiel Command Location: AFRL - Wright Research Sitehttps://www.fbo.gov/index?s=opportunity&mode=form&id=d3e825368b36760b. .. *This is for proposals for a reusable vertical launch, horizontal landing unmanned booster to serve as the first stage of a two-stage-to- orbit (TSTO) system. The description seems to be tailored made for the X-33 suborbital system. I'm inclined to think intentionally so. Then this might open up funding for alternative methods for obtaining lightweight tanks for the X-33 such as the multiple cylindrical tanks method. *It also would make possible a suborbital troop carrier or commercial transport system. More on the Air Force's "Reusable Booster System": USAF Seeks Reusable Booster Ideas. May 14, 2009 By Graham Warwick "The plan is to conduct an integrated demonstration of technologies and processes culminating in a subscale X-plane vehicle that would fly by 2017-18 and take the concept to a technology readiness level of 6, ready to enter full-scale development. "AFRL has several ground-based experiments already under way involving structures, controls and systems for an operationally responsive launch vehicle. The work is focused on a reference concept for an unmanned vertical takeoff and horizontal landing reusable booster capable of turnaround in 24-48 hours and launch within 4-8 hours of a request." http://www.aviationweek.com/aw/gener...euse051409.xml Spacelift Development Plan. http://www.acq.osd.mil/nsso/conferen...%20Release.ppt Also from the Aviation Week article: "AFRL's reference concept includes an integral all-composite airframe and tank structure that carries both internal pressure and external flight loads. The concept vehicle is powered by pump-fed liquid-oxygen/ hydrocarbon rocket engines." The suggestion to limit the fuel to hydrocarbon rather than the higher energy liquid hydrogen probably stems from the fact that for this purpose the vehicle only needs to have a max speed in the range of Mach 3.5 to 7, as indicated by slide #5 in the "Spacelift Development Plan" powerpoint presentation. However, all three competing proposals for the X-33 liquid-hydrogen fueled vehicles, which needed to get to Mach 13+, probably could be adapted to use hydrocarbon fuel, for this Mach 7 max. proposal. This would be another method to effectively re-open the X-33 competition. The X-33. It's back on, baby! X-33. http://www.astronautix.com/lvs/x33.htm http://www.deskpicture.com/DPs/Astro...33Concepts.jpg Bob Clark |
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