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I've been thinking alot recently about how much I'd like to develop a SpacePlane for orbiter that's within the bounds of modern technology. I have never made any new vessels for orbiter before, but I have a pretty good understanding of how the API works. I'm a pretty decent coder, but not very good with modelling. Perhaps some other people interested in working on something like this would like to make this into a team project. Heck, if it works and appears feasible, we can sell the design to someone and get rich  I love flying the DeltaGliderEX alot, and that would be the ideal goal of my project, except I want to eliminate everything on the DGEX that's not currently possible with modern day technology. Primarily this means the engines, and because of this, we'll need a serious reduction in mass to make conventional engines work. My first thought is that it should probably have conventional turbojet engines for the initial ascend as high as it can before firing rockets for second stage. I also think that having external drop tanks would be the best way to minimize mass. I've done 1 drawing for a possible concept, but i think before i share my drawings we could maybe come up with a list of requirements.... Can we perhaps start a discussion about what it would take to build a realistic horizontal takeoff and landing spaceplane?
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You mean you want a SSTO (or stage-and-a-half, anyway) vehicle with runway takeoff and landing? That's a tall order! You're right about needing drop tanks, of course. In fact, using chemical propellants you need a very large tank, so large, in fact, that you may need some big JATO rockets just to get off the ground. I would forget the airbreathing jets, too. If you take off and leave the atmosphere fast enough you won't need them, you can live without them for landing, and the engines, tankage and plumbing, and kerosene jet fuel are just a drag on payload weight which you will only use for a few minutes at the end of the mission. So, it seems that you will come up with something that looks like this:   And, that is exactly what engineers came up with, of course. But there have been lots of other ideas proposed, both for the STS and other programs. Look up Lockheed's Starclipper (and check out Sputnik's cool addon), the VentureStar, and two-stage versions of the space shuttle with fly-back first stages. Of the above vehicles, the one that most closely resembles what you're asking for is the Starclipper, which was a lifting body with a conformal expendable drop tank. Other than the tank, it was resusable and you didn't have to send out ships for an expensive SRB recovery and refurbishment operation. It even had turbojets, which probably would have been removed from a final design. During the development of the shuttle, airbreathing jets were found to be so much dead weight, and power-off landings from steep, fast glideslopes were found to be easier for test pilots, who demonstrated that it was easier even in a B-52. The only thing the Starclipper doesn't do is take off from a runway.
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I sort of have to disagree about the airbreathers. They take up weight yes, require extra...stuff, but if they draw from the same tank and share some of the hardware with the rockets, they could be feasible. I know this is SciFi, but in Stargate on the F-302, the Aerospike engines share a common exhaust manifold with the low-alt airbreathers. It could even be feasible to (if this was really for real  ) create a hatch assembly that closes the turbine part once fast enough for the scrams to kick in, then close those to allow the rockets to kick in. The challenge of designing a spaceplane is to be able to reduce as much weight as possible while continually increasing performance. IF three engines could share as much as possible including the exhaust manifolds, you're shaving...hacking a lot of weight out right there. Another thing to consider is the mission. Is this to be a cargo hauler? Passenger ferry? Interplanetary explorer? The destination. LEO? HEO? GEO? Moon? Inter? And with the mission comes the sizes of the stuff needed to carry out the mission. One person? Whole crew? Few small satelites? Whole Dyson Sphere?
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Ok lets come up with some requirements for our SpacePlane. One thing I'd particularly like to see is that it's capable of powered flight to landing so that it can be flown to any major airport in the world. Could we feasibly develop something that can takeoff and land from a 10,000 ft runway (~3000 m)? If we did this, then the only criteria of a Spaceport over an Airport would be the presence of liquid oxygen and liquid hydrogen on hand. And about the drop tanks... would there be any possible way we could not use them? If the airframe was big enough to hold all the fuel mass internally how much mass are we really saving by using a drop tank? Can turbojets run on LH ?
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reverend said "Can turbojets run on LH? Have you seen this engine design? http://www.reactionengines.co.uk/sabre.htmlBest wishes, N.
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Is this a theoretical engine design, or has it been tested and proved? Or if it's not real yet, and tested, are there any signifigant doubts that it will work?
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reverend wrote:
Is this a theoretical engine design, or has it been tested and proved? Or if it's not real yet, and tested, are there any signifigant doubts that it will work?
Those are all good questions, good in the sense I can't answer any of them! However, reading between the lines on their website, I'd say they are working on the technolgies, but no working complete engine yet. They appear to be part of the LAPCAT program:- http://www.esa.int/techresources/ESTEC-Article-fullArticle_item_selected-7_2_01_par-30_1129904712655.htmlBest wishes, N.
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Well, if you don't want to have any ascent propulsion in it, its very easy to make a space plane...at least from the mass budget. The main problem will be the mass of the crew compartment in the front, which is quite Heavy, while you would like to have the CoG in the back close to the CoP.
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Urwumpe wrote:Well, if you don't want to have any ascent propulsion in it, its very easy to make a space plane...at least from the mass budget.
The main problem will be the mass of the crew compartment in the front, which is quite Heavy, while you would like to have the CoG in the back close to the CoP.
Thinking more about it, I'd like to see a design that could fly from point to point on earth, be refueled, and be able to return. A system requiring drop tanks would rule this out as a possibility unless spare tanks were kept at each airport. drop tank recovery would be a tremendous pain in the butt, so how about lets plan to have an entirely self contained fuel system. Along these lines, to carry the ascent propulsion onboard, we're gonna need some pretty big tanks... like most airplanes where the fuel is stored in the wings, I think this is the way to go. As far as overall size, I'm thinking something about the scale of a 737 is what I'm looking for. The wings of a 737 definetley could not hold the necessary fuel for LEO operations, so I was thinking something more along the lines of a 'flying wing' concept, like a B2 bomber... This could allow for forward and aft, left and right fuel tanks. CoG can be managed by fuel transfer between the tanks.
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reverend wrote:
Thinking more about it, I'd like to see a design that could fly from point to point on earth, be refueled, and be able to return. A system requiring drop tanks would rule this out as a possibility unless spare tanks were kept at each airport. drop tank recovery would be a tremendous pain in the butt, so how about lets plan to have an entirely self contained fuel system.
Along these lines, to carry the ascent propulsion onboard, we're gonna need some pretty big tanks... like most airplanes where the fuel is stored in the wings, I think this is the way to go.
As far as overall size, I'm thinking something about the scale of a 737 is what I'm looking for. The wings of a 737 definetley could not hold the necessary fuel for LEO operations, so I was thinking something more along the lines of a 'flying wing' concept, like a B2 bomber... This could allow for forward and aft, left and right fuel tanks. CoG can be managed by fuel transfer between the tanks.
Yes, but you would need to launch a very high fuel mass - LH2+LOX would be clearly out because its too volumous in the beginning. What about flyback boosters? With the right spaceport infrastructure you could have a quick turn around - at higher ground costs. And you can have a simpler spaceplane. Two stage to orbit is very realistic currently even with the mass ratios you get for flyback boosters.
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If you can't live with droptanks and must have totally reusable SSTO, VentureStar sounds like the concept you're aiming at, but VentureStar didn't use a runway takeoff, it used a fixed launcher for a near-vertical launch. If you can live with placing launcher and equipment at various airfields, this may be feasible. Keep in mind that this is expensive, and that launches may generate lots of noise complaints.
Urwumpe's ideas for a two-stage flyback system make more sense, and early ideas for the STS included this scheme.
As a fun thought experiment, though, let's take your requirement on face value: Runway takeoff and landing, single stage to orbit and back. What's the payload? 2 guys and a Snickers bar for a few orbits, or something heavier and 2-week missions? Either way this thing is going to be a giant hollow tank with wings, but if you want useful payload it's gonna be way bigger.
EDIT: Thinking more about this, the only way this makes sense is if you develop some futuristic propulsion with super-high Isp and low weight.
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Urwumpe wrote:
Yes, but you would need to launch a very high fuel mass - LH2+LOX would be clearly out because its too volumous in the beginning.
What about flyback boosters? With the right spaceport infrastructure you could have a quick turn around - at higher ground costs. And you can have a simpler spaceplane. Two stage to orbit is very realistic currently even with the mass ratios you get for flyback boosters.
Ok if it's too volumous then what if we increased the size of the ship. This is something I have very little knowledge about, but it's something that anyone in amatuer rocketry probably knows very well, that is, figuring out how much fuel mass is required... Just as a starting point, lets assume the empty weight of the ship is 60,000 kg. with the ability to carry up to 30,000 kg of cargo / passengers. How much LH2/LOX are we talking to put that into orbit from a starting altitude of 18km and an initial speed of ~Mach 1.0? Would C8H18 be a better choice than LH2 ?
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After some discussions on IRC I came up with a few new ideas... 1) To make subsonic and supersonic flight more efficient, the flying wing should change shape slightly 2) Inboard jet engines so the intakes can be sealed during re-entry 3) Re-entry, maybe someone with some more knowledge on this subject could speak to it... magnets and plasma. I've read a number of times that plasma can be deflected using a magnetic field. Could a field be placed around the ship for re-entry, or atleast infront of the wing leading edges. This is to keep the plasma from directly contacting the skin of the ship, but also i wasn't sure if the plasma even existed in that state before hitting the skin... so i don't know if this is useable, or within the state of the art, since I do want to stay within the range of modern technology. 4) Using 90000kg as a rough estimate of ship weight + cargo/passengers, this is roughly 10,000kg smaller than the shuttle, so a nearly equal amount of LH2/LOX would be needed, or about 740,000kg. So a total ship mass at take off of ~830,000kg. Would 2 Pratt and Whitney PW2030 (757 engines), which are rated at 193 kN each, is that enough to be able to get airborne on a 10000ft runway?
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reverend wrote:
Ok if it's too volumous then what if we increased the size of the ship. This is something I have very little knowledge about, but it's something that anyone in amatuer rocketry probably knows very well, that is, figuring out how much fuel mass is required...
Just as a starting point, lets assume the empty weight of the ship is 60,000 kg. with the ability to carry up to 30,000 kg of cargo / passengers.
How much LH2/LOX are we talking to put that into orbit from a starting altitude of 18km and an initial speed of ~Mach 1.0?
Would C8H18 be a better choice than LH2 ?
Well, The core stage of the Delta IV weighs 26,760kg and has a gross mass (with fuel) of 226,400kg. So, your talkin alot of fuel. Another thing you have to consider is, although LH2/LOX take up more volume other fuel choices have less energy per cubic meter. So it's a trade off, but my personal opinion is to stick with LH2. But before I go any farther I would like to say.... It is a near imposibility to make a HTOVL SSTO craft. Andy is very right. You need better fuel efficiancy. If you wanted to strech the limits of "modern tech" then use something like 500-600 ISP motors. This could NOT be done with COTS tech. Ofcoure these statments come with a disclamer.... I'm just an un-educated aerospace welder and this is just by opinion. But I have been looking at this problem for the better part of 6 years. Ok, continuing with technical questions. Will the PW2030 engines work with that weight, sure but you'd have to make the wing pritty darn strait and long to create more lift which is not very condusive to speed. The PW4074 would be better but I'm not sure if this design path is the right choice. If you did a realistic weight assesment of wings, engines and such you would probably find you have to heavy a craft. Plus, as someone pointed out earlier, you would need two differnt types of fuel on board. Variable geometry wings are also very heavy. That is alot of hardware to make the wing move and still be capable of handeling a decent G load. The only way to get around all of this is to have multy phase engines, again like someone else sayed earlier. Start off as turbo jets, convert to ram at mach2, convert to scram at mach 5 and finaly rocket at Mach 10-12. Althought there is no known engines that work like this, it has been therorized for 20+ years with the Aurora. I really think you should consider a VTOL or VTOHL if you want to keep it in COTS/modern tech relm.
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That makes sense. The way I look at it, trying to treat a spacecraft like just another airplane is a blind alley. For now, we have to resign ourselves to the fact that an airport and a spaceport are not the same thing, just as we had to give up on the idea of seaplane ports for long distance travel when jet aircraft became the norm.
It might be more useful, once you've got some viable designs for reusable spacecraft, to equip them to use a common infrastructure of launch and landing facilities, similar to the way that any sailboat can use a similar size dock, or an airport can handle any jetliner up to a certain size. So you would have a set of launchpads at each spaceport which can handle any of a certain class of spacecraft, perhaps with adapter fittings and such for different vehicles or configurations. The pad complex would have standard plumbing fittings for LH2, LOX, and say, kerosene, as well as He and N2. You would also need a runway big enough to handle all the vehicles in that class, and postflight servicing gear.
Once you settle for this scheme, you can work on a reliable VentureStar-type class of vehicles and make them reliable, cheap to operate, and quick to turn around between flights. That's the hard part, of course, just ask the STS folks. But if you can pull it off, you can install launch and land facilities at various airfields around the world and build a network of spaceports. The vehicles could ferry fly between them in suborbital trajectories, when needed, so you can cut down on costly 747-shuttle-style movements.
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Absolutly Andy. Standardized launch and landing equip. At some point there has to be a standard for this stuff, like the media and electronics people setteling on DVDs and Blue Ray. Also, going back to some of the reverend's ideas. P2P (point 2 point) should be a heck of alot easier. But you really don't need powered descent. With a little planning You should be able to point and glide to where you want. Lets say you where going to take off from Edwards and fly to the Cape. The powered ascent portion of that trip is only going to be a fraction of the total length, the rest will be coast and glide descent. With that flight profile you cold land anywhere from South carolina to Cuba by changing course early in the ascent or, mid Georgia to Miami if you changed your mind over Texas. A good test for this the the X-15 Delta. You could just scale up the the X-15 Delta to fit 6-8 people. Of course the X-15 Delta is launched from the XB-70 doin Mach 4 at 80,000 ft. Thats the thing, you waste so much rocket fuel starting from 0 and excellerating, though I don't see why you could have a fully thottlable rocket for a HTOHL and you take off at say 30% thrust.
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anemazoso wrote:Of course the X-15 Delta is launched from the XB-70 doin Mach 4 at 80,000 ft. Thats the thing, you waste so much rocket fuel starting from 0 and excellerating, though I don't see why you could have a fully thottlable rocket for a HTOHL and you take off at say 30% thrust. The flyback booster vehicle could be part of the standard launch facilities stationed at each spaceport, though this adds to cost and complexity. SSTO is possible, but with current propulsion technoogy you must compromise: big payload = cost and complexity and multistage system, simple SSTO with VentureStar-style launcher = smaller payload. You must pick one.
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anemazoso wrote:
Well, The core stage of the Delta IV weighs 26,760kg and has a gross mass (with fuel) of 226,400kg. So, your talkin alot of fuel. Another thing you have to consider is, although LH2/LOX take up more volume other fuel choices have less energy per cubic meter. So it's a trade off, but my personal opinion is to stick with LH2.
Yes, I agree that LH2 is going to be the fuel of choice, so my next question here is, can the PW2030's be run on LH2 instead of JetA, perhaps with some minor modifications? Quote:But before I go any farther I would like to say.... It is a near imposibility to make a HTOVL SSTO craft. Andy is very right. You need better fuel efficiancy. If you wanted to strech the limits of "modern tech" then use something like 500-600 ISP motors. This could NOT be done with COTS tech. Ofcoure these statments come with a disclamer.... I'm just an un-educated aerospace welder and this is just by opinion. But I have been looking at this problem for the better part of 6 years. I'm currently thinking that equipping this plane with 3 or 4 SSMEs Quote:Ok, continuing with technical questions. Will the PW2030 engines work with that weight, sure but you'd have to make the wing pritty darn strait and long to create more lift which is not very condusive to speed. The PW4074 would be better but I'm not sure if this design path is the right choice. If you did a realistic weight assesment of wings, engines and such you would probably find you have to heavy a craft. Plus, as someone pointed out earlier, you would need two differnt types of fuel on board. So if I was going with a flying wing design similar to that of B2 bomber, I'd want to minimize the sweep of the wings to get more lift? Also, I was thinking the PW2030 would be a better choice over the PW4074 only because of size concerns. Whereas these jets are going to be inboard (like on a fighter jet). IIRC, the outer diameter of the PW4074 is roughly the same as that of a 737 fuselage... Quote:Variable geometry wings are also very heavy. That is alot of hardware to make the wing move and still be capable of handeling a decent G load. The type of geometric change i was imaginging would be to the angling on the top part of the wing to generate less turbulence at supersonic speeds. I don't know if this will even be a concern in the upper atmosphere so i'm also not sure of this is even necessary Quote:The only way to get around all of this is to have multy phase engines, again like someone else sayed earlier. Start off as turbo jets, convert to ram at mach2, convert to scram at mach 5 and finaly rocket at Mach 10-12. Althought there is no known engines that work like this, it has been therorized for 20+ years with the Aurora. I really think you should consider a VTOL or VTOHL if you want to keep it in COTS/modern tech relm. I was thinking of only using the phases of turbojets for takeoff and ascent to ~ 18km, then rocketting the rest of the way. Might it be possible to save some oxidizer by using like 50% oxidizer, 50% air intake between 18km and 40-45km? It seems to me though that a HTOL would be more fuel efficient than a VTOL... when the shuttle flies, it uses half of it's fuelmass just getting thru the lower atmosphere without really gaining much speed... Am I missing something here? Quote:Also, going back to some of the reverend's ideas. P2P (point 2 point) should be a heck of alot easier. But you really don't need powered descent. With a little planning You should be able to point and glide to where you want. The idea of having the powered descent is so that after the ship passes down below 60,000ft it can 'merge' with regular air traffic. So a space flight arriving at JFK Intl. Airport could fit in and fly amongst the rest of the airtraffic in the area without being a major disruption to the traffic flow. the majority of the descent would be just a simple unpowered glide, the jets wouldn't need to kick in at until the very end... Andy44 wrote:The flyback booster vehicle could be part of the standard launch facilities stationed at each spaceport, though this adds to cost and complexity. SSTO is possible, but with current propulsion technoogy you must compromise: big payload = cost and complexity and multistage system, simple SSTO with VentureStar-style launcher = smaller payload. You must pick one.
If I had to pick one I'd go with a flyback booster... something like a C5 cargo plane using a tow cable or something, but this is why we'd put some big jet engines on it, so that a booster or other type of launch system isn't necessary...
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reverend wrote:
Yes, I agree that LH2 is going to be the fuel of choice, so my next question here is, can the PW2030's be run on LH2 instead of JetA, perhaps with some minor modifications?
I'm not sure but I think it would require substantial modifications. But! Doing some more research has garnered some interesting things. I think SABER is a viable solution. The guys working on it actually build an air breathing rocket in the '80s known as the RB545, but not much is known about it because it's highly clasified. Then theres ATREX which is a Japanies development. This ATREX I think would be great. You can use it from the ground out to mach 6 and descent, then use your SSME's (which I think you should consider using the planned modified RS-68s for Ares V) for the rest of the excceleration. reverend wrote:
So if I was going with a flying wing design similar to that of B2 bomber, I'd want to minimize the sweep of the wings to get more lift?
How about a lifting body design? You get the best of both worlds. Venture-Star-ish/ X-38/ HL-20 style ( Wiki artical , Astronautix artical ) If you were to agment a lifting body design with a little more wing you could get it to take off at a relativly convetional speed and distance. reverend wrote:
t seems to me though that a HTOL would be more fuel efficient than a VTOL... when the shuttle flies, it uses half of it's fuelmass just getting thru the lower atmosphere without really gaining much speed... Am I missing something here?
No, thats a good point but there aren't a whole lot of examples for HTOL SSTO's so I can't really argue I would suspect that the energy requiered is the same or more for HTOL because you will spend more time fighting the atmosphere. But you won't have to carry as much oxydizer. So maybe HTOL would come out on top. (?)
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reverend wrote:
If I had to pick one I'd go with a flyback booster... something like a C5 cargo plane using a tow cable or something, but this is why we'd put some big jet engines on it, so that a booster or other type of launch system isn't necessary...
Well, the problem is the wing mass - for vertical take off or captive carry, you need only small wings, only large enough for landing a almost empty mass. A horizontal take-off SSTO needs very heavy wings, making the dry mass higher. You could eg go for an additional kerosine tank for initial takeoff and landing, but use LH2 rocket engines for boost to orbit. The advantage would be that you can purge the hydrogen+oxygen tanks after reaching orbit and forget any additional thermal control. And you can use off-the-shelf jet engines - eg the powerful F-16/F-15 engines, which could be strong enough for pushing something large to Mach 2.3 at high altitude. But you would only save a little bit from the 9200 m/s total impulse to get into orbit this way. I have calculated a spaceplane which would use a single airstarted SSME to get from Mach 7.5 to 250 km LEO. Starting at 2250 m/s, i calculated the need for ~6000 m/s to enter orbit.
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