A kerosene-fueled X-33 as a single stage to orbit vehicle.
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From: Robert Clark on 3 Jul 2010 11:03 On May 4, 1:49 pm, Robert Clark <rgregorycl...(a)yahoo.com> wrote: > On May 3, 6:31 am, "Androcles" <Headmas...(a)Hogwarts.physics_z> wrote: > > > > > > > No matter which way you slice it, lifting a mass against gravity > > will give it potential energy to fall again. Putting it in orbit means > > giving it kinetic energy as well. During re-entry both the KE and > > PE are lost as heat, which is why all vehicles designed for re-entry > > have heat shields. So at the end of the excursion, with energy > > being a conserved quantity, all of the energy in the fuel has been > > converted to heat which is then radiated into space. > > Your problem isn't to find a trajectory, it is to find how to put > > mass into orbit at minimum cost. That is, find joules per dollar > > for the type of fuels and oxidants and the technology available, > > whether it iskerosene-oxygen, hydrogen-oxygen, old rubber tyres, > > nitromethane for "Top Fuel" drag racing or nitro-glycerine! > > ... > > Nowhere in your analysis above have you considered that. > > > The laws of physics and chemistry cannot be defeated, it is only economics > > that you can meddle with, joules per dollar. I have to tell you honestly > > that you'll never convince an aeronautical engineer of your quick fix, > > you've left out far too much reality. > > The advantage of usingkeroseneor other dense propellant is that in > the same size vehicle you can carry much more propellant. Since the > cost of a launch vehicle is strongly dependent on its physical size, > by using dense propellants you get more joules per dollar. > Note that another key aspect of having a vehicle so weight optimized > that it can be SSTO, is that if you do want to get a larger payload to > orbit you can use those SSTO vehicles in stages. Since they are so > weight optimized, these weight savings can go to carrying greater > payload. > We'll estimate the payload we can loft to orbit with twoX-33'smated > in bimese fashion, where two similar vehicles serve as the first and > second stages. See for instance the attached image from this report: > > Simulation and Analyses of Staging Maneuvers of Next Generation > Reusable > Launch Vehicles. > Bandu N. Pamadi1, Thomas A. Neirynck2, Peter F. Covell3 > NASA Langley Research Center, Hampton, VA > Nathaniel Hotchko4, David Bose5 > Analytical Mechanics Associates, Inc., Hampton, VAhttp://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.81.4885&rep=... > > Figs 1-4, Bimese booster and orbiter.http://i42.tinypic.com/14a92y9.jpg > > Using two similar reusable vehicles for both stages has been estimated > to save on development costs. > The reconfiguredX-33with three NK-33 engines we calculated to have a > dry weight of 21,700 kg, and carry 307,000 kg of kero/LOX propellant. > However, to maximize performance we'll use aerospike nozzles on the > engines. The NK-33 had a 331 s vacuum Isp. But this is because the > engine had a nozzle that was a compromise between optimal sea level > and vacuum performance. With an aerospike nozzle it could get the ca. > 360 s vacuum Isp of other Russian high performancekeroseneengines. > We'll also take its sea level Isp as the ca. 331 s of some first stage > optimized Russian engines. > Since the vehicles will be mated symmetrically instead of one standing > vertically atop another, what I'll call the first stage or booster is > the one that stops firing first, separates from the second one, does > not go to orbit, and returns to the launch site. The second or upper > stage, or orbiter, will be the one that goes on to orbit. > We'll have all 6 engines firing from bothX-33'sfor the first part of > the trip. However, we want to have the upper stageX-33to be fully > fueled for the second stage firing, so we'll use cross-feed fueling to > have fuel from the first stage provide the fuel for the upper stage > also for the first portion of the trip where they are still connected. > Let's calculate the payload that could be carried, taking again the > required delta-V as 8,500 m/s. Take as an estimate 35,000 kg for the > payload. The gross liftoff mass will then be 2x21,700 + 2x307,000 + > 35,000 kg = 692,400 kg. The amount of fuel we'll be using for this > first portion of the trip will be the amount stored in the booster, > 307,000 kg, then this stage will separate and return to the launch > site. The total mass at the end of this first portion will be 385,400 > kg. For this first portion of the trip I'll take the Isp as the > midpoint of the sea level and vacuum values so 345 s. Then the delta-V > we can reach for this first portion will be 345*9.8ln(1 + > 307,000/385,400)=1,981 m/s. > For the second portion of the trip with just the upper stage > remaining, the propellant mass will again be 307,000 and the mass at > the end of this final burn will be 21,700 + 35,000 kg = 56,700 kg. So > the delta-V reached here will be 360*9.8ln(1+307,000/56,700) = 6,557 m/ > s, for a total delta-V of 8,538 m/s. > This is for using kero/LOX as propellant. But this is not the most > efficient dense propellant combination to use. Others can result in > even greater payload to orbit. For instance as described here some > hydrocarbon fuels when also densified by subcooling could result in > 50% greater payload than kero/LOX: > > Alternate Propellants for SSTO Launchers. > Dr. Bruce Dunn > Adapted from a Presentation at: > Space Access 96 > Phoenix, Arizona > April 25 27, 1996http://www.dunnspace.com/alternate_ssto_propellants.htm > > So possibly we could get 52,000 kg payload to orbit. What would be the > launch costs? I estimated before a single reconfiguredX-33might cost > $4,500,000 per launch: > > Newsgroups: sci.space.policy, sci.astro, sci.physics, > sci.space.history > From: Robert Clark <rgregorycl...(a)yahoo.com> > Date: Thu, 18 Mar 2010 12:02:10 -0700 (PDT) > Subject: Re: Akerosene-fueledX-33as a single stage to orbit > vehicle.http://groups.google.com/group/sci.space.policy/msg/ffdb7503f156553e?... > > So lets say the bimese launcher would cost twice this to $9,000.000 > per launch. Then at a 52,000 kg payload, this would amount to a > $9,000,000/52,000kg = $173/kilo cost to orbit, or only $80/lb, a > *major* reduction in the costs to orbit. This would in fact be a revolutionary reduction in cost, by *two orders* of magnitude. To put this in perspective, SpaceX is only offering to reduce the costs by a factor of two. SpaceX also stated man rating their Falcon 9/Dragon system would cost $300 million: Is It Safe? The first company with a planand a rocketto send humans to orbit answers the existential question. * By Michael Milstein * Air & Space Magazine, May 01, 2009 http://www.airspacemag.com/space-exploration/Is-It-Safe.html?c=y&page=2 This is for the cost of an escape system and flight tests. But undoubtedly the largest portion of that cost would be for the flight tests at about $50 million per launch of the Falcon 9. You would want to do at least 4 of 5 launches unmanned before attempting manned launches. Note though for the bimese X-33 at only $9 million per launch you could do over 30 test flights before doing a manned flight. In regards to the efficiency of the bimese system, where you use similar vehicles for each stage, this report also argues it would be lower cost due to lower development costs and lower both dry mass and gross mass than other multi-stage architectures: Launch Vehicle Sizing Benefits Utilizing Main Propulsion System Crossfeed and Project Status. F. Chandler and M. Scheiern, The Boeing Company R. Champion and P. Mazurkivich, NASA Marshall Space Flight Center http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20030002800_2002111035..pdf See the image of the first page of the report here: http://i46.tinypic.com/jpetzn.jpg Bob Clark |