Whilst NOT denying the general "draw" of having a spaceship take off and land "..as God and Robert Heinlien intended them too"; i.e. vertically in both aspects, (for example the German BETA SSTO concept found here: http://ntrs.nasa.gov/archive/nasa/casi. ... 007333.pdf) there is also something to be said about using aerodynamic lift and the ability of horizontal take off and landing vehicles to possibly interface with and operate from every-day aerospace operational systems such as airports.Such a possible system is described in several of the papers listed below:http://ntrs.nasa.gov/archive/nasa/casi. ... 001816.pdfhttp://ntrs.nasa.gov/archive/nasa/casi. ... 012293.pdfhttp://ntrs.nasa.gov/archive/nasa/casi. ... 017286.pdfhttp://ntrs.nasa.gov/archive/nasa/casi. ... 001795.pdfhttp://ntrs.nasa.gov/archive/nasa/casi. ... 012304.pdfhttp://ntrs.nasa.gov/archive/nasa/casi. ... 017829.pdfIn general consisting of some sort of "low-speed" booster using air-breathing engines to fly to a determined altitude and speed before being staged, with the "orbital" portion of the vehicle being a Near-SSTO rocket powered vehicle. The combined effect of this type of Two-Stage-To-Orbit vehicle is that it reduces somewhat the general 'requirements' of having a dedicated "rocket-launch-infrastructure-and-associated-range" which currently is quite a large "chunk" of the change that is associated with Vertical-Take-Off launch vehicle operations. (See: http://www.transterrestrial.com/archive ... ollide.pdf which shows a good breakdown)The ability for self-ferry of the space vehicle and numerous abort options of course make this an attractive option for space access, however the "down-side" most often cited against this concept is that instead of designing, developing, and production of a SINGLE vehicle, you now have to develop TWO seperate vehicles: A rocket orbital stage and a more conventionally powered but normally SUPERSONIC carrier vehicle. Almost doubling your intital cost estimates, and probably overall hurting your operations economics because of the general lack of usefullness today for a supersonic transport aircraft usable by general aviation therefor limiting economic options for multipe uses of the booster aircraft.In addition the overall size of the payload to orbit of the orbital segment has found to be highly effected by the seperation velocity, launch path angle-of-attack and altitude of the carrier vehicle during launch, (found here: http://www.airlaunchllc.com/AIAA-2008-7835-176.pdf, page-3 Section-III "Other than the carrier aircraft size, we had previously found in references 2 and 3 that carrier aircraft launch velocity had the largest effect on payload size, followed by launch flight path angle, and finally launch altitude.") usually translating to larger payloads requiring larger carrier aircraft, OR higher-seperation speeds, OR higher alittude, but more than usually all of the above.The "solution" arrived at by AirLaunch LLC, (see:http://www.airlaunchllc.com/TechPapers.html#) has shown that a fairly economical proposal for air-launching of a rocket can be found using an "off-the-shelf" 747 freighter aircraft with modifications to carry a 3-barrel-Two-Stage-To-Orbit vehicle capable of delivering around 8,000 to 10,000lbs to orbit.If one is willing to increase performance of the launch vehicle itself from the pressure-fed VPaCK system to a more complex pump fed system payload can probably be increased at the expense of some additional costs overall for the launch vehicle system.The carrier aircraft is also still capable of being used as either a freighter or possibley a fire-fighting tanker aircraft which lends economics to the operations of the air launch system simply by allowing "off-time" money to be made when not launching rockets.Overall though the "carrier-aircraft" launch system is self limiting as to size of the payload unless a custom aircraft is built which again highly increases the monies needed to implement the system.Still, as pointed out by the AirLaunch paper cited above, a generally higher seperation velocity relieves the launch vehicle of delta-V requirements usually well in excess of other requirements.For example, on average seperation at Mach-0.8 and 20kft will require around 27.9kft/s delta-V where as a seperation velocity of Mach-3.0 would require only 24.0kft/s from the orbital vehicle, and seperation at Mach-5.5 drops the delta-V to a little over 20.7kft/s required.(From: http://www.ai.mit.edu/projects/im/magnus/bh/analog.html, "Black Horse: One Stop To Orbit")Of course that means you need a large, supersonic carrier aircraft to achieve those speeds... Or do you?One concept I've found interesting is the Langley "Spacejet" which is considered a "Two-Stage" to-orbit system but instead of a "carrier-aircraft" the spaceplane/orbital vehicle is a winged vehicle to which two (or more) turbojet "booster-pods" are attached for low speed take off, taxi, ferry, and initial acceleration flight. See these papers for reference:http://ntrs.nasa.gov/archive/nasa/casi. ... 003229.pdfhttp://ntrs.nasa.gov/archive/nasa/casi. ... 020560.pdfhttp://ntrs.nasa.gov/archive/nasa/casi. ... 066456.pdfhttp://ntrs.nasa.gov/archive/nasa/casi. ... 015826.pdfThis reduces the costs associated with airframe development to quite a bit less than a fully intergrated carrier-vehicle and generally boils the low-speed-to-Mach+ vehicle down to its most basic form. The boosters consist of little more than an aerodynamic frame, engines and fuel which attach to the spaceplane/orbiter and are remotly controlled by the pilots of that vehicle.On the other hand the above studies pretty much concentrated on at LEAST Shuttle-capacity payloads so the booster pods themselves were huge things with anywhere from 8-13+ High Technology advanced supersonic engines per booster. Needless to say the "economics" factor again rears its head as something only a government could afford to build.However...What if you set your sights a little lower and instead of a baseline of "50,000lbs+" to orbit you started with a smaller spaceplane and only around 1,000lbs, even 10,000lbs to orbit? Something the size of the "Black Horse" noted above? Your booster pods can be a LOT smaller and less expensive to develop, especially if you can use "off-the-shelf" engines such as the P&W or GE low-bypass turbofans from military aircraft. You can probably get away with only one or two per 'pod' and get good flight characteristics. Especially if you add something like Mass Injection Pre-Compressor Cooling (MIPCC) to increase thrust and expand the Mach envelope of the engines themselves. (Mach-4 becomes possible at altitudes of over 80kft, with a possilbe doubling of payload over the baseline Mach-0.8 Black Horse design) Granted that designing and building the "pods" will not be cheap, nor easy as compared to say doing the same with a simple set of rocket booster pods, but the operational flexibility along with the ability to interface with existing aerospace cargo and passenger systems would seem to be a large factor in favor of a design like this. In additon the overal "stress" of vertical launch of a horizontal lifting-vehicle are reduced due to the overall lifting-trajectory flown in this concept.Discussion?Comments?Randy
Yeah, for some unknown reason, direct links to NASA NTRS usually don't work at all. You'd better opening the Pdf and paste the adress Let's try this (Gommersall SSTO. How about that ?) http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930074048_1993074048.pdfCheers !
Wrap 'url' '/url' around the links, there's an insert hyperlink button in the edit box above (2nd bottom left)
Arrgghhh! and I can't seem to access the New Mars Forums at all, and none of the correctional stuff I've tried to the original post seems to be working either..Randy
Are the booster pods just engine pods or do they include tankage (other than for return)? If it's just engines, would this be easier or cheaper than flyback boosters? And if it's engines and tanks, is this different from flyback boosters? And are flyback boosters considered difficult or just expensive? I would have thought that if you knew how to design a parachute recoverable booster and how to build a cruise missile you'd have enough knowledge to build a flyback booster. Are there any major unsolved problems or is it just a matter of money? Questions, questions...
Quote from: RanulfC on 10/12/2010 02:47 pmArrgghhh! and I can't seem to access the New Mars Forums at all, and none of the correctional stuff I've tried to the original post seems to be working either..RandyI haven't been able to access New Mars, either -- might be down for maintenance, could be a DNS problem -- just wanted you to know "it's not just you"!
Flyback boosters would be considered BOTH difficult and expensive mostly because of the current flight rate of vehicles being so low.
Quote from: RanulfC on 10/12/2010 03:55 pmFlyback boosters would be considered BOTH difficult and expensive mostly because of the current flight rate of vehicles being so low.I was thinking about something as rugged as Shuttle SRBs, but with liquid propellant and therefore higher performance, which would immediately be lost by having to carry an airbreathing engine and landing gear.
Maybe you could get the airbreathing engines to pay part of their way by engaging them on the way up too, but that would be optional. You might not end up with something that was much more powerful than the SRBs, but you wouldn't need the heavy and expensive solid infrastructure and recovery and refurbishment of the boosters either. So it could still be more economical. Would this be difficult to do? Sounds straightforward, but that can be deceptive.
Ha! Just what I wanted to talk about. Another very cool concept is the Glenn GTX, either standalone or augmented with solids. For one, it looks like a bleeping Colonial Viper!
(As a note on this point, an LRB for the Shuttle would actually probably be cheaper than the SRBs simply because you don't have to ship them all the way back to Utah to be "refurbished" and "refueled" and then back to Florida for launch. Overall the processing for such a booster would simply be: tow-back, wash-out, operations check and refuel. Unfortunatly the idea of replacing the SRBs with more efficient LRBs has always foundered on the rock of politics)
The politics applies to NASA's flag ship rocket. Some experimental launch vehicle may not have the same restriction.
