A kerosene-fueled X-33 as a single stage to orbit vehicle.
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From: Robert Clark on 27 Nov 2009 11:15 On Nov 21, 9:59 am, Robert Clark <rgregorycl...(a)yahoo.com> wrote: > ... > The same reconfiguration of the Lockheed version of the X-33 to dense > fuels and engines to transform it into a full orbital vehicle would > also work for the other proposed half-scale suborbital demonstrators. > The McDonnell-Douglas version was essentially the DC-X, scaled > somewhat larger. See the linked image. I don't know how much the McD-D > version of the X-33 would have cost. However, according to this > Astronautix page a 1/2-scale version of the full orbital DC-Y had been > proposed, but not funded, which would have cost in the range $450 > million, compared to the $60 million of the DC-X, in 1990's dollars: > > DC-X2.http://astronautix.com/lvs/dcx2.htm > > This would have just below suborbital to suborbital performance, but > the price would be significantly less than the DC-Y full orbital > version of $5 billion: > > DC-Y.http://astronautix.com/lvs/dcy.htm > > However, the point is some preliminary calculations show this 1/2- > scale DC-X2 should be able to carry enough dense hydrocarbon fuel > under such a reconfiguration to reach orbit. So you would be able to > get a reusable SSTO prototype at a significantly reduced price than > the $5 billion suggested for the full DC-Y vehicle program. > > Bob Clark > > Figure 5: X-33 Concept Art from McDonnell Douglas (Frassanito, J., > McDonnell Douglas).http://vorlon.case.edu/~jam64/images/SSTO/SSTO_Figure_5.jpg > > taken from: > > Single Stage to Orbit: > A Reliable Transport System or an Unattainable Dream?http://vorlon.case.edu/~jam64/work/ssto.htm Guys, it's a simple equation to see why a reusable SSTO vehicle should be possible. It has been often noted that the 1960's era Titan II first stage in itself had single-stage-to-orbit performance, though it would have had minimal payload capability: SSTO Cons. "A SSTO vehicle needs to lift its entire structure into orbit. To reach orbit with a useful payload, the rocket requires careful and extensive engineering to save weight. This is much harder to design and engineer. A staged rocket greatly reduces the total mass that flies all the way into space; the rocket is continually shedding fuel tanks and engines that are now dead weight. "Although a SSTO rocket might theoretically be built, margins would be likely to be very thin- even comparatively minor problems may tend to mean that a project to achieve this could fail to achieve the necessary mass-fraction to reach orbit with useful payload. "Single-stage rockets were once thought to be beyond reach, but advances in materials technology and construction techniques have shown them to be possible. For example, calculations show that the Titan II first stage, launched on its own, would have a 25-to-1 ratio of fuel to vehicle hardware.[1] It has a sufficiently efficient engine to achieve orbit, but without carrying much payload.[2]" http://en.wikipedia.org/wiki/Single-stage-to-orbit#SSTO_Cons See the section on Titan II first stage fully fueled mass and empty mass here: Titan. "Stage1: 1 x Titan 2-1. Gross Mass: 117,866 kg (259,850 lb). Empty Mass: 6,736 kg (14,850 lb). Motor: 2 x LR87-7. Thrust (vac): 2,172.231 kN (488,337 lbf). Isp: 296 sec. Burn time: 139 sec. Length: 22.28 m (73.09 ft). Diameter: 3.05 m (10.00 ft). Propellants: N2O4/ Aerozine-50." http://www.astronautix.com/lvs/titan.htm The two LR-87-7 engines used had a mass of 713 kg each, for a total of 1426 kg: LR87. "Engine Model: LR87-7. Manufacturer Name: AJ23-134. Government Designation: LR87-7. Designer: Aerojet. Propellants: N2O4/Aerozine-50. Thrust(vac): 1,086.100 kN (244,165 lbf). Thrust(sl): 946.700 kN (212,827 lbf). Isp: 296 sec. Isp (sea level): 258 sec. Burn time: 139 sec. Mass Engine: 713 kg (1,571 lb). Diameter: 1.53 m (5.00 ft). Length: 3.13 m (10.26 ft). Chambers: 1. Chamber Pressure: 47.00 bar. Area Ratio: 9.00. Oxidizer to Fuel Ratio: 1.90. Thrust to Weight Ratio: 155.33. Country: USA. Status: Study 1961. First Flight: 1962. Last Flight: 2003. Flown: 212." http://www.astronautix.com/engines/lr87.htm Most of the remaining empty mass of 5310 kg for the Titan II first stage would be structural mass, the propellant tanks, support structures, etc. This would be primarily aluminum and steel. Since a 1/3 to 1/2 weight saving can be made over aluminum and steel by using carbon composites, an all composite construction could save at least 1,770 kg off the vehicle empty mass. However, probably we would have to swap out the engine because as described here, the LR-87-7 engine was not throttlable, which would be needed for a SSTO: -------------------------------------------------------------- Newsgroups: sci.space.tech From: henry(a)spsystems.net (Henry Spencer) Subject: Re: Is Roton Dead? Date: Tue, 9 Jan 2001 21:11:51 GMT In article <93eaqs$6a4$1(a)mulga.cs.mu.OZ.AU>, David Kinny <dnk(a)OMIT.cs.mu.oz.au> wrote: >>...in fact, the central problem with using >>the Titan II first stage as an SSTO is that it has *too much* thrust to >>fly an efficient trajectory. > >How exactly does too much thrust prevent flying an efficient trajectory? >Difficulties in flipping over to horizontal? Or something else? Basically, in the time it takes to climb clear of the atmosphere, it picks up too much vertical velocity. This thing was an ICBM, designed to move out fast... and flying as an SSTO, it hasn't got a hulking great second stage on top to slow it down. (In fact, a secondary problem of having too much thrust is the bone-crushing acceleration toward the end, when the tanks are almost empty.) An SSTO launcher wants to take things a bit slower, so that it can tip over to horizontal gradually, as it leaves the atmosphere, and still have most of its fuel left for horizontal acceleration. You can't just throttle back the engine, first because it wasn't throttlable :-), and second because you need to keep it operating efficiently, which throttling usually sacrifices to at least some extent. However, *reducing* the performance of an engine is usually not a difficult engineering problem! -- When failure is not an option, success | Henry Spencer henry@****.net can get expensive. -- Peter Stibrany | (aka ****@zoo.toronto.edu) http://yarchive.net/space/launchers/ssto.html -------------------------------------------------------------- I suggest the NK-33 be used. It was designed for kerosene/LOX but quite likely would also work with the N2O4/Aerozine-50 propellant of the LR-87-7 because the LR-87 engine was variously used with N2O4/ Aerozine-50 and kerosene/LOX. Using a single NK-33 would also save 200 kg off the vehicle dry weight: NK-33. http://www.astronautix.com/engines/nk33.htm The question is could we use that approx. 2,000 kg saved weight for landing gear and thermal protection to make the vehicle reusable? Let's take the landed weight as still 6,736 kg where we used the saved weight for landing gear, thermal protection, and payload. The landing gear for an aerial vehicle is commonly taken as 3% of the landed weight: Landing gear weight. http://yarchive.net/space/launchers/landing_gear_weight.html So this is 202 kg. To make a powered vertical landing the common estimate is 10% of the vehicle landed weight has to be used in propellant: Reusable launch system. Vertical landing. http://en.wikipedia.org/wiki/Reusable_launch_system#Vertical_landing So 673 kg. For thermal protection, we'll assume it'll make a ballistic reentry, base first. For this vehicle the base will only be 3 meters wide, for an area of 7 m^2. Using base first reentry we'll have to cover primarily the base only: Blue Origin New Shepard. "A passenger and cargo spacecraft has considerably less need for cross- range." .... "As a result, the craft is much "rounder" than the DC-X, optimized for tankage and structural benefits rather than re-entry aerodynamics. It has not been stated if the vehicle is intended to re-enter base-first or nose first, but the former is most likely for a variety of reasons. For one, it reduces heat shield area, and thus weight, covering only the smaller bottom surface rather than the much larger upper portions. The area around the engines would likely require some sort of heat protection anyway, so by using the base as the heat shield the two can be combined. This re-entry attitude also has the advantage of allowing the spacecraft to descend all the way from orbit to touchdown in a base-first orientation, which would seem to offer some safety benefits as well as reducing aero-loading issues." http://en.wikipedia.org/wiki/Blue_Origin_New_Shepard We'll use the high temperature resistant but low maintenance metallic shingles developed for the X-33: REUSABLE METALLIC THERMAL PROTECTION SYSTEMS DEVELOPMENT, http://reference.kfupm.edu.sa/content/r/e/reusable_metallic_thermal_protection_sys_117853.pdf The areal density of this is in the range of 10 to 15 kg/m^2. This will then require 70 to 105 kg to cover the base only. Then the total mass for landing and thermal protection is 980 kg, and about 1,000 kg could go to payload. This would be only 0.8% of the gross mass but would be a reusable SSTO vehicle. It might be possible to improve this payload fraction by using kerosene/LOX instead of the N2O4/Aerozine-50 propellant. This would result in a higher Isp, however the N2O4/Aerozine-50 is denser and so more fuel can be carried. Bob Clark
From: Robert Clark on 28 Nov 2009 11:24 It is important to remember that single-stage-to-orbit in itself is not impossible. It was in fact proven to be feasible from the early days of the space program: Single-stage-to-orbit. SSTO Cons. "Single-stage rockets were once thought to be beyond reach, but advances in materials technology and construction techniques have shown them to be possible. For example, calculations show that the Titan II first stage, launched on its own, would have a 25-to-1 ratio of fuel to vehicle hardware.[1] It has a sufficiently efficient engine to achieve orbit, but without carrying much payload.[2]" http://en.wikipedia.org/wiki/Single-stage-to-orbit#SSTO_Cons Such a vehicle of course while carrying minimal payload would also not be reusable. The question is could you replicate this performance using lightweight materials so this weight savings could go to reentry and return systems and could this be done economically? I already gave the argument that the weight savings possible from composite construction makes such a reusable SSTO possible. The reason why I say it is now economically feasible is because lightweight carbon composite construction is now being planned for some passenger cars. Consider the price for carbon composites in the early 90's: G.M. to Show a High-Mileage Experimental Car By DORON P. LEVIN, Published: Monday, December 30, 1991 "At the North American International Auto Show in Detroit next week, G.M. will show its Ultralite, which the company says can produce 100- mile-a-gallon fuel efficiency at 50-mile-an-hour highway speeds. "That efficiency is possible, G.M. said, because the car weighs only 1,400 pounds. (A Chevrolet Corsica, which is approximately the same size as the Ultralite, weighs about twice as much.) Scaled Composites Inc. of Mojave, Calif., built the Ultralite body for G.M. "Although many race cars are made of carbon fiber, which is quite sturdy, the material is enormously expensive compared with steel or aluminum. But G.M. said it had received a patent for a process that sharply reduces the cost of carbon fiber, which currently is about $40 a pound, compared with about 35 cents a pound for steel." http://www.nytimes.com/1991/12/30/business/gm-to-show-a-high-mileage-experimental-car.html So the price then was about 100 times greater than steel. You wouldn't see many all-composite-construction rockets at those prices even if even then it would have made a reusable SSTO possible. Now look at the price given in this article from the year 2000: Carbon-Fiber Composites for Cars. "To meet the ultimate PNGV mileage goal, one potentially enabling technology is to use carbon-fiber composites, which form the structure of U.S. fighter jets. Carbon-fiber composites weigh about one-fifth as much as steel, but can be comparable or better in terms of stiffness and strength, depending on fiber grade and orientation. These composites do not rust or corrode like steel or aluminum. Perhaps most important, they could reduce vehicle weight by as much as 60%, significantly increasing vehicle fuel economy. "The problem is that carbon-fiber composites cost at least 20 times as much as steel, and the automobile industry is not interested in using them until the price of carbon fiber drops from $8 to $5 (and preferably $3) a pound. Production of carbon fibers is too expensive and slow." http://www.ornl.gov/info/ornlreview/v33_3_00/carbon.htm Now this British company claims their patented process allows composite construction both for the chassis frame and the body panels at low cost for a passenger car to be introduced next year: Axon announces affordable, 100mpg, carbon-composite passenger car. "Axon has gone simply for an uncomplicated 500cc engine in a low- weight body, which replaces the traditional heavy steel or aluminium frame with recycled carbon fibre composites - as strong as steel but only around 40% as heavy. Extensive use of carbon materials through Axons cars makes a massive impact on the power-to-weight ratio, meaning they can get acceptable overall performance using a much smaller, lighter and more frugal engine. "The lightness and strength of carbon fibre have been well-known for decades - its been cost thats prevented this wonder-material from popping up all over the automotive world, restricting it to top-end specials and aftermarket goodies. But its here that Axon claim to have made a breakthrough." http://www.transport20.com/uncategorized/axon-announces-affordable-100mpg-carbon-composite-passenger-car/ Because of the rate at which the costs of carbon composite production is decreasing, I argue the production cost for a reusable SSTO using carbon composite construction, because the lighter weight in materials required, will soon be comparable to that of an expendable rocket using standard, heavy construction materials. And it is already now economically feasible due to lower per use costs of a reusable vehicle. It is also extremely important to keep in mind that such a reduction in structural mass for a rocket would result in a comparable reduction in engine mass. This is important because the engine mass is the second greatest component for the dry mass of the rocket after the structural mass. The reason this engine mass reduction occurs is exactly analogous to why it occurs when replacing the structural mass of cars with lighter materials: Carbon Fibre Reinforced Composite Car. Primary author: Andrew Mills Source: Materials World, Vol 10, no. 9 pp. 20-22, September 2002. "In the area of vehicle design, body weight is the most important target for improvement, as a reduction in the weight of a vehicles body means that a smaller engine, and a lighter drive train and assembly can be used. This benign spiral leads to further mass reductions, so much so that various studies have indicated a potential for savings of up to 65% by using carbon fibre composites instead of steel wherever possible." http://www.azom.com/Details.asp?ArticleID=1662#_Background Bob Clark Axontex chasis. http://www.transport20.com/gallery/albums/Axon/axontex_chassis.jpg
From: Robert Clark on 29 Nov 2009 06:48 LORAL Space Systems, the leading communications satellite builder, had a design for a single-stage-to-orbit though expendable launcher. They expected to use all-composite cryogenic tanks on these launchers to save weight. Their idea was that the high cost of launch is from trying to assure high reliability. However, their launchers were to be designed to be used for payloads such as replacing consumables on the ISS, launching propellants to orbital depots, etc. They were able to conclude based on study of prior launchers that high reliable launchers cost more and correspondingly lower reliable ones cost less. They therefore specifically aimed for a rather low reliability rate of about 66% to get low cost. They figured this would be allowable for low cost items such fuel and consumables. Still, it is interesting that their low cost design was specifically based on a SSTO, composite-tank rocket: Aquarius: Low-Cost Low Reliability Consumables Launcher. Enabling Technology includes large, lightweight liner-less composite tanks. http://homepage.mac.com/fcrossman/NorCalSAMPE/Comp_WS_papers/Turner_012204.pdf Aquarius. "Proposed expendable, water launch, single-stage-to-orbit, liquid oxygen/hydrogen, low-cost launch vehicle designed to carry small bulk payloads to low earth orbit. A unique attribute was that low reliability was accepted in order to achieve low cost." http://www.astronautix.com/lvs/aquarius.htm Bob Clark
From: Robert Clark on 1 Dec 2009 09:26 On Nov 29, 6:48 am, Robert Clark <rgregorycl...(a)yahoo.com> wrote: > LORAL Space Systems, the leading communications satellite builder, > had a design for a single-stage-to-orbit though expendable launcher. > They expected to use all-composite cryogenic tanks on these launchers > to save weight. Their idea was that the high cost of launch is from > trying to assure high reliability. However, their launchers were to be > designed to be used for payloads such as replacing consumables on the > ISS, launching propellants to orbital depots, etc. > They were able to conclude based on study of prior launchers that > high reliable launchers cost more and correspondingly lower reliable > ones cost less. They therefore specifically aimed for a rather low > reliability rate of about 66% to get low cost. They figured this would > be allowable for low cost items such fuel and consumables. > Still, it is interesting that their low cost design was specifically > based on a SSTO, composite-tank rocket: > > Aquarius: Low-Cost Low Reliability Consumables Launcher. > Enabling Technology includes large, lightweight liner-less composite > tanks.http://homepage.mac.com/fcrossman/NorCalSAMPE/Comp_WS_papers/Turner_0... > > Aquarius. > "Proposed expendable, water launch, single-stage-to-orbit, liquid > oxygen/hydrogen, low-cost launch vehicle designed to carry small bulk > payloads to low earth orbit. A unique attribute was that low > reliability was accepted in order to achieve low cost."http://www.astronautix.com/lvs/aquarius.htm > > Bob Clark Nice list of launch vehicle designs, including some SSTO's going back to the 60's: Space Future - Vehicle Designs. http://www.spacefuture.com/vehicles/designs.shtml Here's a review of SSTO concepts proposed over the years: History of the Phoenix VTOL SSTO and Recent Developments in Single- Stage Launch Systems. Gary C Hudson http://www.spacefuture.com/archive/history_of_the_phoenix_vtol_ssto_and_recent_developments_in_single_stage_launch_systems.shtml And this article argues that SSTO performance has long been possible for expendables, and that a reusable one is possible with modern materials: Launch Vehicle Design. "Contrary to what many people who make expendable rockets will tell you, it isn't difficult to design a "single stage to orbit" ( SSTO) rocket. In fact it's very easy - it can be done with rocket engines and propellant tanks designed, manufactured and operated 20 years ago! It's important to know this, because a lot of people will try to tell you otherwise. "A Thought Experiment "This very idea was written up by Gary Hudson in "A Single-Stage-to- Orbit thought experiment". "If you attach 6 SSMEs (Space Shuttle Main Engines) directly to a Space Shuttle External Tank ( ET), you could launch 30 tons payload to orbit. It wouldn't be an economical way to launch - but it's certainly possible. But please note: it's only possible taking off vertically; no-one can build a horizontal take-off SSTO. "But, of course, if you carry passengers to orbit you'll want to bring them back - and that's what's tricky: to build a fully reusable SSTO, not an expendable, one-way ride. " http://www.spacefuture.com/vehicles/building.shtml As this article notes, many people don't think a SSTO vehicle is possible even with expendables. That is why with the rapid drop in the cost of composite materials I'm arguing that small test vehicles of all-composite construction should be built to prove the principle of SSTO at least for expendables. This would be possible and affordable to do even for the smallest of the New Space companies with in house construction of the composite materials. Then when it is seen that SSTO, though not reusable, performance is possible for an actual working rocket, it will be more believable that following well-known scaling principles that larger rockets should allow reusable versions with significant payloads. Bob Clark
From: Robert Clark on 8 Dec 2009 09:50
On Nov 28, 11:24 am, Robert Clark <rgregorycl...(a)yahoo.com> wrote: > ... > > Now this British company claims their patented process allows > composite construction both for the chassis frame and the body panels > at low cost for a passenger car to be introduced next year: > > Axon announces affordable, 100mpg, carbon-composite passenger car. > "Axon has gone simply for an uncomplicated 500cc engine in a low- > weight body, which replaces the traditional heavy steel or aluminium > frame with recycled carbon fibre composites - as strong as steel but > only around 40% as heavy. Extensive use of carbon materials through > Axons cars makes a massive impact on the power-to-weight ratio, > meaning they can get acceptable overall performance using a much > smaller, lighter and more frugal engine. > "The lightness and strength of carbon fibre have been well-known for > decades - its been cost thats prevented this wonder-material from > popping up all over the automotive world, restricting it to top-end > specials and aftermarket goodies. But its here that Axon claim to > have made a breakthrough."http://www.transport20.com/uncategorized/axon-announces-affordable-10... > > Because of the rate at which the costs of carbon composite production > is decreasing, I argue the production cost for a reusable SSTO using > carbon composite construction, because the lighter weight in materials > required, will soon be comparable to that of an expendable rocket > using standard, heavy construction materials. And it is already now > economically feasible due to lower per use costs of a reusable > vehicle. > Video of SpaceShipTwo assembly, showing the all-composite construction, including the structural members: SpaceShipTwo Assembly. http://www.youtube.com/watch?v=B8XaJbwwT68 Bob Clark |