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#11
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market size as a function of launcher size
Parallax wrote: Dick Morris wrote in message ... Parallax wrote: Although it would be very nice to have a very heavy launcher like Saturn V or Energia, there is little market for it. The small market doesn't justify development or the infrastructure for it. The market can handle various smaller launchers. Is there any way to use combinations of smaller launchers to achieve a very heavy launcher when it is needed without developing the infrastructure for the very heavy launcher? A medium-lift (which I define to be 40-80,000 lb. payload) launcher can substitute for an HLLV in some circumstances, such as manned lunar or Mars flights. A large majority of the Initial Mass in LEO (IMLEO) of a lunar or Mars ship will be propellants, which are easily divided into smaller packages. Several tanker flights of a medium-lift RLV can deliver propellants to a propellant depot in LEO. An additional flight can deliver the hardware, which is then docked to the propellant depot where the tanks are filled. That eliminates the need for an HLLV and gives us a vehicle which can be used for many other purposes as well. In some cases, this could work. However, if the medium lifter is expensive, then several are even more so. My proposal is for a medium-lift, VTOL RLV, so the recurring cost would be quite low. The recurring cost for the 4-6 RLV flights to do a manned lunar or Mars flight would be much less than the recurring cost of an expendable HLLV required to launch the same payload mass. Is the cost proportional to the number of launches? Would the cost be significantly less with fewer but larger launches? Truax says the cost does not increase significantly with rocket size so big rockets are about the same overall cost as smaller ones to launch (cost is mostly overhead). The total cost-per-flight is not a linear function of either vehicle size or flight rate. Other factors being equal, a large rocket will have a lower recurring-cost per pound of payload than a smaller rocket due to economies of scale, but the large rocket will have a lower flight rate for a given mass of payload delivered to LEO, so the fixed-cost per flight will tend to be higher. You'd have to plug some actual numbers into a spreadsheet to know which is cheaper. However, there is little need for HLLV but when it is needed, it might really save $ if the development and overhead cost ws not much more more than a smaller rocket. So, this means that clustering smaller rockets might make sense if these smaller rockets are used when smaller payloads are desired. Clustering of existing booster stages would work, and would save a substantial amount of development cost vs. starting from scratch with a unitary design. Historically, development cost tends to scale as the dry mass to the 2/3 power, so even if the clustered module was a new design, it would save a significant amount of development cost vs. a new unitary design. For this, hybrids might really make sense. They are fairly simple and reliable with better performance than pure solids. They are almost environmentally benign and some of the fuels (and oxidizers) are very safe and easy to handle. Maybe the H2O2/Wax combination would be good for this. Here's a program for calculating the performance of propellant combinations: http://www.dunnspace.com/isp.htm One could imagine very cheap production of many of these engines and an easy clustering system for arbitrary enlargement. Tow the cluster to near the equator in the ocean away from silly govt regs, tilt it upright as in Seadragon and launch. Each engine could be fed from a common oxidizer tank with its valve independently controlled to balance the cluster thrust or to shut one down if it went bonkers. Outer engines in cluster could be fed oxidizer to burn faster for faster staging and then are ejected from the core. Inner engines initially have low thrust but on staging they pour it on. Forget reuseability, this is cheap enough to throw away after each use. I disagree that there will ever be a launch vehicle that's cheap enough to throw away after each flight and be low enough cost to generate any significant new markets. If Mr. Truax, or anybody else, thinks they can prove otherwise, they are certainly welcome to try. No nasty Nitrogen tetroxide, no ammonium perchlorate, no cryogenics, just cheap, reliable, few safety problems and environmentally benign. I know I greatly oversimplify, but basically take a large wax cylinder, drill a hole down the middle, wrap the outside with fibreglass cloth, carbon fiber matting using boat building technology so its done in quantity, add the nozzle and pressure and temp guaging, and a computer controlled throttle valve. Oxidizer tanks are made from welded Al with carbon fiber matting around outside resined on. Its just a Little Dumb Booster that can be clustered to make various sized Big Dumb Boosters when needed. The devil's in the details ;-). (A company by the name of OTRAG tried something similar back in the late 70's and was not successful. Don't remember exactly why. Their modules used pressure-fed storable liquids.) I clearly have too much time on my hands since I know little about rockets. Use some of the first problem to deal with the second. Get a copy of "Rocket Propulsion Elements" by Sutton for a comprehensive treatment of the principles of rocket propulsion. See also a book called "Modern Engineering for Design of Liquid-Propellant Rocket Engines" by Dieter Huzel (one of the Von Braun team at Peenemunde), and others, for more details on actual hardware design. Those are college level books, but you can certainly find more basic information on the web if you want to. |
#12
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market size as a function of launcher size
On Tue, 23 Sep 2003 20:50:02 GMT, in a place far, far away, Dick
Morris made the phosphor on my monitor glow in such a way as to indicate that: I disagree that there will ever be a launch vehicle that's cheap enough to throw away after each flight and be low enough cost to generate any significant new markets. If Mr. Truax, or anybody else, thinks they can prove otherwise, they are certainly welcome to try. Sea Dragon was meant to be reusable. -- simberg.interglobal.org * 310 372-7963 (CA) 307 739-1296 (Jackson Hole) interglobal space lines * 307 733-1715 (Fax) http://www.interglobal.org "Extraordinary launch vehicles require extraordinary markets..." Swap the first . and @ and throw out the ".trash" to email me. Here's my email address for autospammers: |
#13
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market size as a function of launcher size
Rand Simberg wrote: On Tue, 23 Sep 2003 20:50:02 GMT, in a place far, far away, Dick Morris made the phosphor on my monitor glow in such a way as to indicate that: I disagree that there will ever be a launch vehicle that's cheap enough to throw away after each flight and be low enough cost to generate any significant new markets. If Mr. Truax, or anybody else, thinks they can prove otherwise, they are certainly welcome to try. Sea Dragon was meant to be reusable. OK. Make that "If anybody thinks..." -- simberg.interglobal.org * 310 372-7963 (CA) 307 739-1296 (Jackson Hole) interglobal space lines * 307 733-1715 (Fax) http://www.interglobal.org "Extraordinary launch vehicles require extraordinary markets..." Swap the first . and @ and throw out the ".trash" to email me. Here's my email address for autospammers: |
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