If it's just the engine cycle itself, ie the thermodynamic cycle, then it probably doesn't need to include any specific information on the heat exchangers and frost control mechanisms. And is it the SABRE 3 or SABRE 4 engine cycle? What might the USAF gain from studying the thermodynamics of the engine cycle? ie what applications or insights might it give them for future planning? Is it like JS19 suggests - the only real reason for studying the cycle in this engine is to look at possible applications for launch capacity only.
Quote from: MichaelBlackbourn on 03/01/2015 06:00 pmAny chance we can hack a ramp into the bottom of the payload bay for paratrooper deployment? Baumgartner up some airborne troops and fire them off the back of the ramp.How does the payload bay compare to a c130 in number of troopers. And can the craft slow down long enough and low enough to deploy them and then land far downrange? Or maybe a disposable frame that gets ejected and then drops the troops.Welcome to the forum. The bay is about 4.8m wide and about 16 m long. There is no option for a "tail ramp" type drop.
Any chance we can hack a ramp into the bottom of the payload bay for paratrooper deployment? Baumgartner up some airborne troops and fire them off the back of the ramp.How does the payload bay compare to a c130 in number of troopers. And can the craft slow down long enough and low enough to deploy them and then land far downrange? Or maybe a disposable frame that gets ejected and then drops the troops.
Unfortunately you're either going to need various bases at different longitudes to minimize plane change payload losses or you have a fairly small minimum team the system can use. If the vehicle is staying orbital to land further along track or plane change back to its launch base that means the personnel are carrying out individual reentries, or you have to do an orbital ejection of a re entry capable lander module while keeping the vehicle in tact. Either way a huge challenge. Probably the closest to this architecture is the "Q bay" of the U2 and it's developments, built as a simple rectangular duct running top to bottom, but I'm not sure what facilities it supplied to the payload or if they were more or less self contained.
Option B is to have the vehicle already into a reentry so a chunk of velocity is already lost. Now you're looking at something like an ejection. The highest is about M3 from an SR71, however it seems due to the altitude (around 80 k feet) which apparently equates to something like 400mph. This is one of those sounds-cool-but-is-really-nonsense ideas that's great for the plot of a straight-to-download action movie. IRL not really that good.
Just considering the first one then, since they would seem impossible to reconcile,...
... what they have in mind would seem to be an LH2-fuelled skylon-like carrier, dropping a jet-fuelled lander (since ability to retrieve troops and craft was a desired characteristic), equipped with heat shielding. Even if a suitable heat shield material was available, the main problem seems to be with the skyon-like carrier - what happens to it after release? If it goes to orbit once-around, then maximum payload for the lander is limited to in the region of Skylon's 15 tons. If it is on a suborbital trajectory, it would re-enter in uncontrolled airspace, and would have to be refuelled at a LH2-capable runway.
Build a heat-shielded jet aircraft lighter than 15 tons or maintain a network of LH2-capable runways in hostile regions, neither seems particularly feasible
In retrospect it would actually have been neat to be able to have the option of supersonic dash into AO, drop to high-subsonic and dump the payload pod, then dash back up to supersonic for egress. But you still have all the issues of inserting into hostile territory with minimum forces that is inherent in the system. Hmmm, something more like a supersonic "Pack-Plane" maybe? (http://en.wikipedia.org/wiki/Fairchild_XC-120_Packplane) But the differences between with and without aerodynamics would probably be prohibitive let alone hypersonic and/or suborbital...
DROP TROOPERS! U2: Power and air conditioning as far as I know. The constraints were that the equipment had to fit into the bay and work on the provided air and electric.
Still need a pod or something to hold the troops together unless they individually have some sort of propulsion and guidance. HALO's do something similar from similar altitudes but they have control over their positioning during drop which a supersonic drop would not have. (Imagine your "average" Marine's full kit. Now put a spacesuit on it and him and ask him to perform "simple" maneuvers in the gear. There's a reason the military was interested in the results of high altitude parachuting before Baumgartner did it )And again you get about twice the useful payload to the target with a C-130 than you would with a Skylon under these circumstances...
Quote from: RanulfC on 03/03/2015 09:11 pmhttp://en.wikipedia.org/wiki/Fairchild_XC-120_PackplaneThis is OT but this idea still looks a sensible notion to maximize the use of expensive assets. I don't think anyone doubts that the ISO container has revolutionized how quickly goods can be be moved as holds no longer need to be individually loaded.
http://en.wikipedia.org/wiki/Fairchild_XC-120_Packplane
Approx. 97% off-topic:
The Packplane concept (and Skylon equivalent) is not analogous to ISO containers. Shipping containers are much smaller than the ships that carry them. Ditto palletised cargo that goes in a shipping container or truck box. The pallets/container are much smaller than the cargo-carrier so that you don't have to worry about the vehicle size. A 2 pallet van, a 2x2x5 pallet truck, a 2x2x10 pallet ISO shipping container... A single 2-TEU skeleton trailer, a double-stack 2-TEU train carriage, a 36-TEU river barge, a 5,000-TEU Panamax, etc.But there's no shipping equivalent of the Packplane, where you have a single removable module that becomes a ship's entire hold, even though ships similar to an empty Packplane exist for other purposes, so it's not a structural issue. It would be simple to design a roll-on/roll-off giant freight module for such a ship, but each semi-submersible platform-ship is a unique size, therefore each giant freight module would be bespoke to each ship. You can see where this is going...Similarly, instead of a Packplane, the air-freight equivalent of ISO containers are the much smaller ULD containers, light pallets with corner cutaways to allow them to stack against curved cargo-holds. (Likewise the US military have standardised on their own "master pallet".) A Packplane type system, OTOH, would be unique to each airframe and wouldn't really save you anything in airport handling. It would just add another step to go wrong, another set of equipment to buy to move the Packplane shell around, in addition to the equipment to load the shell (ULDs/master-pallets, forklifts, etc) and support the loaded and uploaded airframe.The launch vehicle equivalent of pallets/ULDs/ISOs would be the cubesats and their racks and launchers. If launch vehicles ever became so large that they routinely shipped dozens of full scale (say 5t) satellites in a single launch, then I suspect something like a 2.4x2.4x2.4m "cubesat" standard would evolve. (2.4m/8ft is pretty common for 3+m shrouds, 4.8m/16ft for 5.5m shrouds. Makes a nice 1U, 2U standard.)Without that, I don't think there's a an advantage in creating a single "Packplane" payload module for a launcher. It doesn't give you "aircraft-like operations". Operationally, it just increases the handling - integrate the payload into the container, then the container into the launcher. So the container is really just wasted payload. It's different if you were routinely trying to integrate 10-20 separate payloads into a single HLV where a size-standardised payload-rack would improve operations enough to justify the rack's mass.
The Falcon-9 with the with an aeroshell that landed a folded up Blackhawk and crew/soldiers was, I thought a nice attempt at addressing the issues
QuoteThe Falcon-9 with the with an aeroshell that landed a folded up Blackhawk and crew/soldiers was, I thought a nice attempt at addressing the issuesWTF ??!!
Quote from: Archibald on 03/06/2015 05:42 amQuoteThe Falcon-9 with the with an aeroshell that landed a folded up Blackhawk and crew/soldiers was, I thought a nice attempt at addressing the issuesWTF ??!! Impressive It only took three days for someone to catch that one. Yup, was a suggested approach I read on an engineering forum. Not QUITE as crazy as it sounds but not far off Randy
We have not seriously explored taking the SKYLON type vehicle up to the heavy lift class but the few “fun exercises” we have done have not shown any fundamental upper limit technically but the economics go to pot. Basically making the systems as small as possible while still capturing the main market (i.e. not small sats) throws the economic burden on to more launches (where reusables score) and off development cost and acquisition cost (where reusable suffer).
If the market for large payloads gets to the point where a bigger vehicle makes sense, someone will design one. Kinda like how locks on the St. Lawrence Seaway have been replaced with bigger ones multiple times as shipping outgrew them.
http://forum.nasaspaceflight.com/index.php?topic=24621.msg735577#msg735577Quote from: HempsellWe have not seriously explored taking the SKYLON type vehicle up to the heavy lift class but the few “fun exercises” we have done have not shown any fundamental upper limit technically but the economics go to pot. Basically making the systems as small as possible while still capturing the main market (i.e. not small sats) throws the economic burden on to more launches (where reusables score) and off development cost and acquisition cost (where reusable suffer).If the market for large payloads gets to the point where a bigger vehicle makes sense, someone will design one. Kinda like how locks on the St. Lawrence Seaway have been replaced with bigger ones multiple times as shipping outgrew them.Alternately, if someone with big plans and deep pockets decides they want a super heavy Skylon-type vehicle for their own purposes, they might pay to get one built; NASA and SpaceX are both doing this already with more conventional launcher technology.
JS19, your argument about 'bulk cargo' makes a lot of sense. Question: if you take out the satellite market, what other bulk cargo could there be? Fuel to depots ?Space station's construction components by other nations ?
Some time ago I read a nice paper about space mining, NEAR EARTH OBJECTS AS RESOURCES FOR SPACE INDUSTRIALIZATION, by MARK SONTER. He makes a strong argument by examining and comparing the mining industry on Earth with space use. One of his conclusions was that it could be possible to build a space craft mining unity that would weight something like 5 metric tonnes. I wonder if something like this could be crammed inside a Skylon standard cargo module, perhaps with a suplementary deep space propulsion unit launched separately (perhaps electric propulsion like Vasimr, that uses argon and hydrogen that could be mined and replenished in situ). This subject has ever surfaced on Skylon threads ?
Skylon kills this business case by providing cheap access. it brings the value of water down from 14k $ per kilo, to 600 $ per kilo.