The 1970’s saw the first major “oil crisis.” The prospect of a world without cheap oil led NASA to seriously contemplate solar power satellites… satellites the size of Manhattan in geosynchronous orbit; covered in solar cells, these satellites would beam hundreds of megawatts of power down to Earth via microwaves.
Something the size of a city could not be conveniently launched atop small launch vehicles. Instead, the cargo launchers would need to be vast… hearkening back to the Post-Nova/Post-Saturn desgins from the early 1960’s.
One such design was Boeing’s “Space Freighter,” a two stage manned and winged vehicle. The first stage was powered by rocket engines burning liquid oxygen with methane; the second stage used LOX and hydrogen. The first stage was equipped with turbojets to allow it to fly back to the launch site; the second stage was a glider, but had the advantage of being able to return at will from low Earth orbit like the Shuttle, and thus was able to glide to the chosen landing site.
Vast as this vehicle was, it still only managed roughly the same payload as the Post-Saturn vehicles from 15 years earlier, with less ability to grow more capable versions.
Scale comparison of the Space Freighter with the Shuttle, Saturn V and a smaller heavy lifter.
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Heavy Lifter options and evolution
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45 Responses to “Space Freighter”
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I’ld still rather have a Star-Raker.
😉
One of the perceived problems with this design was the requirement for the payload to fit in the payload bay. Since the SSPS construction program would have required delivery of raw material instead of finished spacecraft (e.g., structural units, solar cell assemblies, etc.), that was probably not as significant as one might think. Plus, the first stage could be used with a specially configured upper stage for, say, a manned Mars mission launch, if that could be squeezed into one of the planned 1000 launches per year for a 60-satellite, 30-year program.
JSC also looked at launchers in the same class that were conventional two-stage serial staging systems. The larger 2 million pound payload version was something like 80 feet in diameter.
The reentry corridors for that orbiter would have had to be carefully chosen. The shock wave would have blown down buildings. What a behemoth.
You look at the size of the wings on that thing’s two stages, and start extrapolating the number of man-hours that going into inspecting the Shuttle TPS between flights, and you can quickly realize that this is _not_ the way to do it.
Sci-fi monster…
The reason why Boeing turned to Shuttle-like boosters for the SPSS studies was that the payload bacame more “dense” and less voluminous than first envisaged. In fact, the first proposal from Boeing was the famous Big Onion, a sort of pantographed Nexus already illustrated here, optimized for vast, little dense, payloads (folded-up photovoltaic panels). Remember that this was in mid-to-late 70’s, and the problems in Shuttle turn-around times were unknown.
Trying to figure how exactly this gets from the recovery runway back to the launchpad is problematical also.
It dwarfs the Saturn V, and that may make it too large for any sort of crawler transporter extrapolated technology.
You could float it into place horizontally on a giant barge, but how do you get it from the horizontal position on the barge to vertical on the pad?
It’s so tall that a barge wide enough to keep it from toppling over due to the high center of gravity when vertical is going to be a real monster, something like 1,000 feet on a side.
At a launch rate of 1,000 a year, and needing at least a few days (more likely weeks, but I’ll give them the benefit of the doubt here) to turn one around for relaunch, you are talking a fleet of hundreds of these things, along with all the pads for launching them and all the hangers to refurbish them between flights.
The cost would be horrendous, and I don’t know if even a international consortium could support its funding.
>–the SSPS construction program would have required delivery of
> raw material instead of finished spacecraft (e.g., structural units,
> solar cell assemblies, etc.), …
Actually the point was the SSPS would be built from prefabricated parts lifted from Earth – not raw material to be processed in space. This greatly reduced the cost adn complexity of a SSPS project.
>..You look at the size of the wings on that thing’s two stages, and
> start extrapolating the number of man-hours that going into
> inspecting the Shuttle TPS between flights ….
Shuttle TPS was a cluge to avoid metal skined tiles and allow a rivited aluminum hull. They know how to build simpler to service TPS skins.
… Lifting these beasts into a stack in the new VABs you’ll need, and carry them no the new crawler transporters — Well I guess if your doing something no the scale of a fleet of SSPS stations its affordable – but there are simpler ways!!
Well, the all O’Neill idea was to do that just simpler, putting the factories in space near the raw material sources …..
Pat/Marco — the vehicles were towed from the landing site to the refurbishing/processing facility, then to the payload integration facility, then to a transporter-erector-launcher setup where the stages were integrated and the vehicle erected, fueled, and launched. Turnaround was on the order of seven days when the process was fully optimized (two satellites per year).
Kelly — poor choice of words on my part. I did indeed mean sub-assemblies and not sand and bauxite. 🙂
Problem with putting the factories in space is the infrastructure needed in space to manufacture the components — instead of”just” an assembly dock, you’d need a raw material extraction and transport infrastructure from the moon to GEO, plus the assembly facilities, plus the maintenance of all of that.
Only the second stage would need to have complex TPS. The first stage is big enough that even something as simple as thick skins of aluminum would work as a heat sink.
If you’re going to lift cargo like that then just go with Sea Dragon. Simpler and a lot cheaper!
The fuel tanks in the booster seem surprisingly small considering the overall volume of the thing. And why methane?
Methane is denser than LH2, so the tanks are smaller by comparison to the second stage, which used modified SSMEs.
The assumption was that petroleum would be scarce and a fuel derived from coal would be plentiful.
It would be a lot easier to go the VTO/VL route in vehicle design and at least have it in the proper orientation for relaunch on landing.
It doesn’t say what the separation speed of the fly-back first stage is, but both the drawing and painting seem to show it having something like a RCC leading edge on it, and I think the belly would have to be skinned in either titanium or stainless steel at the very least not to get heating damage when it drops back to lower altitude.
Aluminum would be very conductive, but where’s the heat supposed to be dumped to? By the time you got heading home to the recovery site, the whole interior wing structure could be heated up to the melting point by heat conduction from the aluminum skin to the aluminum interior structure. Given the thickness of the wing on the booster I was half expecting to see propellant tanks inside of it also, like on a airliner.
> Aluminum would be very conductive, but where’s the heat supposed to be dumped to?
The aluminum skin itself. Most 2STO design have staging occur somewhere around Mach 5 to 7; I don’t have the number right at hand, but once you get boosters roughly the size of the S-IC stage and bigger, thick aluminum skins start becoming *all* the TPS you need. A half-inch to two-inch thickness of aluminum sounds pretty massive, until you realize that that’s not all that thick compared to the overall dimensions of boosters like the Sea Dragon (which was to be largely aluminum). These thick skins serve as effective heat sinks. Only pointy bits would need special protection… noses, leading edges, edges of underside control surfaces. And with the Space Freighter first stage, the nose is noticably non-pointy.
The bigger the vehicle is, the easier protecting it from re-entry heating becomes. Generally. Keep in mind, heating rates are defined as “watts per square meter,” and whether the vehicle is the size of ASSET or an Imperial Star Destroyer, the heating rates are going to be roughly the same. And the bigger the vehicle, the thicker the skin can get without messing with weights.
At some point, a vehicle could be so big that aerothermal heating simply ceases to be a major concern. A meteoroid of nickle-iron the size of a grain of sand hitting the atmosphere at 40 km/sec with vaporize into a puff of vapor. A meteoroid the size of Texas made of nickle iron hitting the atmosphere at 40 km/sec won’t even notice that the outer few mm of surface have gotten incandescently hot. The percent of the thing vaporized by the atmosphere will be microscopically small prior to it hitting the ground.
Would it have been feasible to build the Shuttle with a reusable metal structure instead of the tiles? I guess they thought it wasn’t cost-effective at the time to use exotic materials, but I wonder how it would have compared in reality. Could something like Ares have a metal or other non-ablative heat shield using modern materials?
Dyna-Soar was going to use a metal structure for its exterior TPS, as was VentureStar. It at least got looked at in relation to the National Aerospace Plane.
Dyna-Soar used an interesting combo idea of allowing most of the structure to become very hot on reentry, while shielding the crew and non temperature resistant systems behind a layer of water between the outer skin and inner hull.
As it heated on reentry, heat was conducted to the water, which sublimated into steam to keep the interior cool.
VentureStar was to use a metallic shingle tile structure over its exterior and its high drag to weight ratio once its propellants were expended to decelerate it quickly on hitting the upper atmosphere and keep peak heating on it below that experienced on the Shuttle, and down in the range that metallic TPS could handle.
Specifics of the TPS on the NASP are either still classified or were never fully worked out in detail. Woven metallic or ceramic materials were to play a part, as they were both more robust than the Shuttle’s fragile silica tiles, and a major aim of the program was to build something that didn’t have the Shuttle’s high inspection and maintenance requirements between flights (another major aim of the program was to make the Soviets think we were developing it as a suborbital nuclear bomber, not a civilian replacement for the Shuttle – so they would spend a whole pile of Rubles trying to counter something that didn’t exist, and maybe wouldn’t work if it did exist – and that part of the program was completely successful, as that’s exactly what they thought it was, and they almost crapped their pants when Reagan announced it.)
One thing that hits me as odd about the Space Freighter design is the choice of Shuttle-style delta wings.
The reason the Shuttle ended up with them is because the military wanted it to have high cross-range on reentry, particularly from polar orbit, to give them more options about the orbits they could use, particularly for single or dual orbit missions where the Shuttle would ascend to orbit, release its payload, and return ASAP before it came within range of Soviet ABM defenses.
This of course immediately convinced the Soviets it was a space bomber, and helped breathe a little last life into their Spiral space fighter program.
Although the Shuttle needed those big of wings, what exactly does the space freighter need them for, particularly on the fly-back booster?
I can see possibly using them on the orbiter to give it more options in getting back from a low inclination orbit where the SPS material is dropped off (though it would make a lot more sense just to build the launch facility near the equator and get a lot better payload to orbit weight that way, as well as simplifying the ascent and return trajectories), but why would the booster need them, given it will be returning to a recovery site without any great need to maneuver on its way home?
Are they simply to keep it from pitching over during ascent due to the big wings on the orbiter, like the added fins on the Dyna-Soar carrying Titans were?:
http://www.biocrawler.com/w/images/f/f4/Dyna_Soar_launchers.png
If so, that’s a pretty clunky way of doing things from a weight viewpoint.
Pat, the booster still needs lift. Yes, the wings counteract the orbiter’s wings, but once staged, the booster has to fly back to metro Titusville and land a la STS.
Yeah, but if it just has to fly back, it doesn’t need anywhere near as large of wings, and the smaller type that the Shuttle would probably have ended up with without the military cross-range requirement would work just fine:
http://www.nss.org/resources/library/shuttledecision/p208.jpg
Assuming you were actually be launching 1,000 missions with these a year for 60 years (the mind boggles at the cost of doing that, no matter how much more efficient than the Shuttle the per-mission economics could be made), then the first thing you would want to do is ditch Cape Kennedy as the launch site, and get something as near to the equator as possible to up payload to orbit on each mission.
Virtually none of the Shuttle/Saturn V infrastructure at the Cape would be usable for this project anyway, so you might as well build a dedicated launch facility for it from scratch on the equator, which would also save the area around it from the acoustic effects of having one of them taking off every eight hours.
Although in this case you don’t have to worry about stages falling on people to your east like in the case of expendable boosters, you may still want to put it on the east coast of something to avoid the possibility of one failing during ascent and falling out of the sky onto someone’s head.
Africa is pretty much out as a launch site due to political instability (that would put it in Somalia, and the last thing we need is Somali space pirates) So that means the two obvious choices are South America or one of the US owned Pacific Islands. Since the system is to run on liquid hydrogen, liquid methane, and liquid oxygen, you would want an area where you could get these in large quantities easily to sustain the expected launch rate.
You could put a nuclear powered system to break down seawater to get the hydrogen and oxygen on one of the Pacific Islands, but what about the methane?
Brazil has easily exploited sources of methane in its vegetation, and hydrogen could also be extracted from the methane pretty easily, leaving just the LOX production, which would use about the same amount of energy no matter where the manufacturing plant was located.
So if I were going to build a launch site for this vehicle, I’d put it in eastern equatorial Brazil, right around the outlet of the Amazon River into the Atlantic near Ilha De Marajo.
(I meant “Orion”, not “Ares” above, of course.)
> George Allegrezza Says:
> May 11th, 2010 at 10:19 am
> Kelly — poor choice of words on my part. I did indeed mean
> sub-assemblies and not sand and bauxite.
😉
Yeah that would just be silly.
> Problem with putting the factories in space is the infrastructure
> needed in space to manufacture the components — instead of”
> just” an assembly dock, you’d need a raw material extraction
> and transport infrastructure from the moon to GEO, plus the
> assembly facilities, plus the maintenance of all of that.
Exactly. O’Niels class assumed launch costs were fixed per pound of cargo, and found with extreamly high ($1000 per pound) launch cost it was cheaper to colonize the moon and space and mine, manufacture, etc the stuuf you assembled nito SSPS’. It wasn’t until the DOE looked at the idea that somenoe asked the aerospace companies what would the launch costs be if you were launching millions to tens of millions of tons a year. Economies of scale and craft like this droped the cost to low tens of $ per pound in current day $’s. At that point the whole Space colonization idea fell through.
😉
>..Sea Dragon (which was to be largely aluminum)…
I thought Sea Dragon was 1-2 inch thich steel for its hull?
> Observer Says:
> May 11th, 2010 at 9:04 pm
> Would it have been feasible to build the Shuttle with a reusable
> metal structure instead of the tiles? ==
Yes, I gather after Columbias (orbiter 101) tile and servicing issues surfaced, Rockwell proposed building the other orbirters to a upgraded 200 configuration with metal clad tiles or skins, easier servicing, etc. NASA turned them down though. I’m guessing they figured it would be embarasing to admint the first one had flaws.
>== Could something like Ares have a metal or other non-ablative
> heat shield using modern materials?
Ares is the throw away boosters so there is no point. If you mean Orion the capsule, its single use also, so still no point.
Course NASA building a fully expendable capsule on booster configuration now a days is nuts!
>.. One thing that hits me as odd about the Space Freighter design is
> the choice of Shuttle-style delta wings.
> The reason the Shuttle ended up with them is because the military
> wanted it to have high cross-range on reentry, particularly from
> polar orbit, ….
That wasn’t the only reasno. The smaller straight wings NASA orogionally planed would have had nasty stability and control problems during reentry — which made the AF very vervious. But raising the cross range issue forced NASA to adopt a far more controlable delta wing – which made the AF much happier.
😉
>..Assuming you were actually be launching 1,000 missions with these
> a year for 60 years (the mind boggles at the cost of doing that, no
> matter how much more efficient than the Shuttle the per-mission
> economics could be made),
;/
Well teh cost per flight would drop down to milions of dollars — but you’ld need to clean up the servicnig issues to even get flight rates that high!
> I thought Sea Dragon was 1-2 inch thich steel for its hull?
As can be learned from Aerospace Projects Review Article 28, “Sea Dragon,” (available for the low, low price of $4.90 from here: http://up-ship.com/blog/blog/?p=5998 ), the first stage of Sea Dragon used 2014-T6 aluminum… 4.17 inches thick for the fuel tank, 2.26 inches thick for the LOX tank. The second stage was far daintier, with walls of the same material only 0.75 inches thick for both tanks.
Kelly Starks wrote:
“That wasn’t the only reasno. The smaller straight wings NASA orogionally planed would have had nasty stability and control problems during reentry — which made the AF very vervious. But raising the cross range issue forced NASA to adopt a far more controlable delta wing – which made the AF much happier.”
I can see that applying to the orbiter, but the fly-back booster will be going a lot slower at separation (Scott thinks Mach 5-7; I’d guess it would be faster than that, at around Mach 8-10, given how much propellant it carries in relation to it’s size) but either way this will be a lot slower than the Mach 25 reentry the Shuttle has to deal with, and occurring in a denser atmosphere as well.
One of the big problems any sort of fly-back booster is going to have to face on reentry that the Shuttle doesn’t is the rapid deceleration that will occur as it falls back into the atmosphere at far suborbital speed.
The reentry trajectory is a lot like the one of the Mercury-Redstone flights, and those pulled a lot of G’s on the way down compared to the gradual deceleration that the Shuttle faces on the way back from orbit.
High G’s mean a strong airframe is needed, and Scott’s idea of the thick underbelly skin may be necessary from a simple structural point of view just to withstand the stress of the reentry; you would have to balance it with a strong set of spars under the upper wing skin so that you would get a I-beam girder effect with strength on both the top and bottom of the wing, but the wing’s thickness is of great help in that regard.
That being said, I still think something resembling a scaled-up X-15 wing would be better overall from a weight standpoint than the Shuttle style wing shown on the booster.
Now, if I’d been designing it, the booster would have something along the lines of the wings shown on the Faget shuttle illustration I linked to, and the orbiter stage would be a wingless lifting body to prevent the wings throwing it off kilter during ascent atop the booster.
Once the orbiter had reentered the atmosphere and decelerated to fairly low speed, swing wings would be deployed from inside of it for landing, thereby removing the need for any sort of TPS on the wings at all.
The overall orbiter would look a lot like the Hyper III design that NASA glide tested with the swing-out wings:
http://history.nasa.gov/SP-4220/p160.jpg
> admin Says:
> May 12th, 2010 at 5:21 pm
>> I thought Sea Dragon was 1-2 inch thich steel for its hull?
> As can be learned from Aerospace Projects Review Article 28,
> “Sea Dragon,” (available for the low, low price of $4.90 from
> here: http://up-ship.com/blog/blog/?p=5998 ), the first stage of
> Sea Dragon used 2014-T6 aluminum… 4.17 inches thick ..
I respect your data and product placement. 😉 But I’m surprized they use such heat intolerant hull material on the Dragons?!
Pat Flannery Says:
May 13th, 2010 at 12:18 am
>== the fly-back booster will be going a lot slower at
> separation (Scott thinks Mach 5-7; I’d guess it would be
> faster than that, at around Mach 8-10, ==
> One of the big problems any sort of fly-back booster is going
> to have to face on reentry that the Shuttle doesn’t is the
> rapid deceleration that will occur as it falls back into the
> atmosphere at far suborbital speed.
>
> The reentry trajectory is a lot like the one of the
> Mercury-Redstone flights, and those pulled a lot of G’s on
> the way down compared to the gradual deceleration that
> the Shuttle faces on the way back from orbit.
One advantage of the larger wings is more area to distribute reentry heat, and more lift, so you can skim along in higher thinner air longer. I think that should mellow out the G loads?
>== if I’d been designing it, ==
> = The overall orbiter would look a lot like the Hyper III
> design that NASA glide tested with the swing-out wings:
>
> http://history.nasa.gov/SP-4220/p160.jpg
Hey I like the FDL-5 design with its swing out wings and drop tanks.
😉
http://www.hitechweb2.szm.sk/Xtras/FDL.jpg
http://www.ninfinger.org/models/stratosphere/fdl5_announce.html
or star clipper
> I’m surprized they use such heat intolerant hull material on the Dragons?!
The intent was “cheap.”
Was the intent to have it melt on reentry?
The upper stage was expected to be expendable, at least initially. The first stage, on the other hand, had massively thick aluminum walls which could soak up a whole hell of a lot of aerothermal heating before damage.
Lockheed built a full-scale mock-up of the FDL-5:
http://www.picturetrail.com/sfx/album/view/8379229
Check the photos on the left side of the page to link to larger images of it. The drop tanks appear to be the same type used on the X-15.
My experence with Aluminum is it warps like hell at far cooler temps. And that melting point of 450F worries me.
Hell modern composites take more heat then that —ok ceramic compositse are rated up to 5400F, but I was thinking more normal composites.
Ooo, Thanks for the url Pat. Can’t access it from the office but I emailed it to home.
Weirdly, some rumors weer that the FDL-5 mockup was so detailed they thought it was really built for some black op. Seems a engine like that specified for it was built and tested – and there was surprizingly little mention of it afterwards.
Unlikely, but it was a pretty decent design for a mini shuttle.
One of my favorite lost designs. 😉
There are photos of the LH2/Florine plug-nozzle engine for it under test on that page too.
The mission might well have been something like the Navy Space Cruiser that Scott has info on in the Aerospace Extras section of his website; that was going to perform satellite inspection or interception in under one complete orbit so that the Russians wouldn’t know exactly why one of their satellites suddenly stopped working while outside of their tracking range.
I can’t believe that FDL-5 could reach orbit on its own with just internal fuel and the two drop tanks, so maybe some sort of carrier aircraft was intended to get it up to altitude and speed before it was released to continue on its own? Rocket-boosted Blackbird?
>.. I can’t believe that FDL-5 could reach orbit on its own with just internal
> fuel and the two drop tanks, so maybe some sort of carrier aircraft
> was intended to get it up to altitude and speed before it was released
> to continue on its own? Rocket-boosted Blackbird?
No I could see it doing it on its own – or perhaps with some kick motors to push it at the start. It depends on how much internal fuel and what the plug nozel engine burns.
The engine was supposed to burn liquid hydrogen/liquid fluorine, a propellant combo that has one of the highest specific impulses possible for liquid fueled engines.
But the hydrogen would be bulky to carry, and the internal volume of the FDL-5 looks to be fairly limited. You could save some space by using slush hydrogen, but even then I suspect it would be air launched at the very least, even if that meant just being carried to altitude by a B-52 like the X-15 was.
An alternative would be that it wasn’t designed for true orbital flight, but rather would just pop up into space to take out a satellite or do a suborbital recon mission and then reenter.
Oh, I did remember liquid Hydrogen. I thought it used a RP/Lox or something dense with powdered metal — so you had a lot of power in a compact tankage. Even LOx/RP I could see making orbit with this. nothing with liquid hydrogen could. Liquide hydrogen works very badly in ships.
>..An alternative would be that it wasn’t designed for true orbital flight, but
> rather would just pop up into space to take out a satellite or do a suborbital
> recon mission and then reenter.
Anto sat you can do from a F-15 or something. Suborbital recon….
Not sure.
If you are going to have the interceptor inspect or take out the target satellite under remote control, you would leave a “paper trail” in the form of the signals going up to it and back.
At least for Space Cruiser, the pilot would do the intercept under manual control so as to maintain “signal stealth” during the mission.
Nowadays it would be possible to program the interceptor to do this under internal control, but things hadn’t advanced that far when FDL-5 and Space Cruiser were proposed.
I was surprised at just how sophisticated the design of the SAINT (SAtellite INTerceptor) was given the time frame it came out of; I was expecting a Agena with a camera on it, but the design looks like something out of SDI program from twenty years later:
http://www.astronautix.com/craft/saint.htm
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