So, for the US, reprocessing must not be economical or it would be happening already.
Freshly-mined uranium is cheap and plentiful and a once-through cycle of mining, enrichment and consumption is less expensive than fuel derived from current spent fuel reprocessing systems, in part because they are based on military-style weapons-grade plutonium production (the PUREX process) since that was the first method developed to deal with spent fuel. There is some research going on into lower-cost and simpler spent fuel reprocessing but it's not a priority given the low cost of fresh uranium and yellowcake production at the moment.
France and other nations such as Russia, Britain and Japan reprocess spent fuel for other reasons -- it vastly reduces the volume of material needing to be stored for long periods of time, for one thing. The Russians are working on advanced fuel cycles to burn spent fuel in fast reactors like the BN-800. Japanese have a breakout capability to make nuclear weapons if they decide to -- The Monju breeder, the reprocessing plant at Rokkaisho and they even have the small Epsilon orbital launcher to repurpose as an ICBM if they choose.
Accuracy per se isn't the real advantage of adding Galileo to the existing Navstar and Glonass global positioning satellite networks since better fix data is more dependent on correction overlay services like WAAS in the US and EGNOS in Europe, using fixed ground stations to provide extra accuracy information to GPS receivers allowing, for example, safe automatic landing of aircraft and shipping movements through restricted waters.
The main benefit of having a lot more GPS satellites in orbit is in places such as cities and mountainous regions where the skyview is restricted and it is possible to lose simultaneous line-of-sight to the four satellites required for a correct position/altitude/velocity result. More satellites means fewer blackouts for a given receiver in such situations.
Technically, a uranium tamper is still fissioned with fast neutron flux
Not quite. Uranium-238, the main component of depleted and also naturally occurring uranium doesn't fission. It WILL breed up into Pu-239 through neutron capture via an intermediate product and that will fission and produce energy if hit by neutrons.
Natural uranium has about 0.6% U-235 which will fission so it's a better tamper than depleted uranium which is usually about 0.2%-0.3% or so, providing more bang for your buck as it only takes one neutron to cause an atom of U-235 to fission whereas the U-238->Pu-239 breeding and fission process requires two neutrons. This all has to happen in a short period of time, too before the expanding bubble of fissionable material gets too large.
Jobs hated holes in his Precious. There are few holes in the current generation of Apple hardware. Jobs adored slim, the new laptops and phones are slimmer than ever. The legacy is being carried on all too well, with a dead man at the helm.
ESA have already put two space observatories, the Herschel infrared telescope and the Planck cosmic microwave background telescope into the L2 location. The JWT is being launched and deployed by ESA so it's not an absolute first for them.
ESA is paying for the launch and that entitles European scientists access to the instrument and data collected by it.
It's going up on an Ariane V launcher using a French-derived LOX/LH2 engine and Italian solid-rocket boosters with a lot of German sparkly bits to do the control.
Saying "the French" is like saying NASA = "Floridans".
And those forward operating bases need to be protected from enemy raids so adding hundreds of troops, vehicles, fuel, logistics etc. to the front lines. The backfield bases operating planes like the F-15SE are usually already in place in friendly territory or on carriers and they can do the same job or better than the A-10 without the frontline logistical load.
Basically the A-10 is an older weapons system in a world which has moved forward. The F-35 is a sniper picking off targets from beyond light AA range (MANPADs, heavy machine guns and rapid-fire cannon) while the A-10 conducts hand-to-hand combat with the enemy if it tries to use its Big Stupid Gun. It's not like it can fly without the BSG either, the entire airframe is built around it. Other aircraft can carry guns with similar capabilities in terms of rate of fire in conformal packs or underwing if the mission requires it but they don't HAVE to cart them around if they're not needed.
The A-10 is stiffy-inducing like battleships. They're obsolete like battleships and a waste of manpower and effort like battleships. There are folks who think battleships should be in the armoury today, for no real reason other than the stiffy they induce. The A-10 is a flying battleship, basically.
Dell's Precision series laptops configured with a Xeon CPU and 64GB ECC DRAM option are not targetted at gamers, they're portable workstations. Same with HP's ZBooks, up to 64GB RAM and NVidia Quadro graphics cards, not an option a gamer would usually choose.
They were built cheap to be flown by ANG pilots over West Germany to get shot down by self-propelled AA guns and short-range missiles deployed with Soviet spearpoint armour brigades. The Big Stupid Gun was designed to chew up personnel carriers and trucks and other targets of opportunity and maybe damage/kill tanks but to use it the pilot had to get within a kilometre or so of the opposition and then fly straight toward them, not a good thing to do against anyone who can shoot back en masse. Times have changed and now there are better CAS weapons in the toolchest -- Maverick, Brimstone etc. which can do this kind of work from tens of kilometres out from any short-range defensive weapon systems that can knock down an attacking aircraft. They need to be deployed by smart platforms like the F-35 although older-generation aircraft like the F-16 can act as ammo mules for them with the F-35's instrumentation and C3 capabilities taking over after launch. The A-10 is too dumb in terms of battlefield networking to be of much use even in this role and besides the single pilot is busy flying the aircraft.
As for fast WWII strike aircraft, the Mosquito and the Typhoon were in the same speed range as the A-10. The F-35, F-15SE and F-18 can be on station in half the time it takes to get an A-10 into position to do some good.
The A-10 needs a full-length runway to operate from unlike the carrier-based F-18 and the F-35. That means several kilometres of airfield perimeter to protect from raids by enemy forces which means lots of troops, logistics etc. A fast CAS/strike aircraft can operate from bases in safe ground far from the enemy and still get to operational areas in time to do some good if needed.
The A-10 isn't in production, the last airframe came off the production line in 1984, over thirty years ago.
There's a porky programme ongoing for Boeing to re-wing some of them since they're falling apart, having been built cheaply to fly and die over the West German countryside against Soviet armour and air defences in an all-out war. Luckily they've not had to face a real air defence network for the past ten years or so but even against the Iraqis severely degraded systems a bunch of them were lost in 2003.
A-10s are not actually very effective in the CAS role, being a single-seater where the pilot has to fly the plane in rough air close to the ground while also identifying targets and delivering fire. The number of blue-on-blue incidents listed against A-10s reflects this time-management problem. They also have to come within reach of ground-based anti-artillery guns to use their Big Stupid Gun rather than standing off and killing the enemy with ranged weapons. Before anyone points out how rugged they are ("titanium bathtub!") remember that significant damage is a mission kill, they have to get out if they get chewed up and leave the ground-pounders to their own devices.
A-10s are surprisingly slow (slower than some WWII strike/CAS piston-engined aircraft!) which means they have to operate from full-sized air bases close to the front line to provide a quick-response CAS capability which in turn require defence from attacks, supply, logistics etc. Any of the really capable CAS aircraft existing today and the future F-35 have speed and range on their side as well as carrier capability which is less logistically intensive. They aren't also sitting ducks in case they operate against anything more dangerous than Bushmen with spears.
Resolution : 32767 x 32767(interpolation), 109 x 61(Physical)
It's purely on-off touch with no pressure-sensitive stylus as the MS device has and which artists and creative types want and need. That's why the CintiQ 27" digitiser display costs $2800 even though its display resolution isn't nearly as good as the Surface device.
From the actual article -- "includes a 28" display with 13.5 million pixels at a 4500x3000 resolution"
The standard 4k resolution mentioned was a comparison, not part of the spec of the Surface. As for the price comparison, please add in the cost of a high-definition screen-based digitiser to the Apple iMac spec and get back to us. Oh, the iMacs don't have a built-in screen digitiser as an option? Oops.
...with the original article. If "the missile will weigh up to 10 tons" then it's not going to get very far laden down with "up to 10 tons of nuclear cargo".
Deary deary me. I suspect the translation service they used (Google Hackslate, perchance or Bing Ablator) got stuff very very wrong.
Looking at it without the hype the new missile is an upgraded version of an older design with similar capabilities. It's probably constrained to fit into existing land-based silos the same way the US Trident missile upgrades were. The MIRV payloads may be getting updated to ensure penetration of close-in missile defence systems like Standard and Patriot plus possibly a target-seeking option to allow for hitting a US CVBG on the high seas, and that extra capability may be why they're building something with more payload capability than the older SS-18. I'd expect them to reduce the total number of ready missiles as they decommission their older missiles though.
Thorium (Th-232) isn't fissile, it needs to be bred up into U-233 to produce energy. U-233 works quite well in a nuclear weapon core (the US fired off at least two test devices back in the day). The U-233 in a proposed thorium reactor is pure, it has no contaminants that make it difficult to weaponise by an unscrupupous operator.
There are very few commercial breeder reactors still around or in operation since mined uranium is cheap and plentiful and breeders generally have a poor operational record, something that does not bode well for any thorium reactor that might be built since they share a lot of the same engineering technology (very hot compact core, solid moderator, very high neutron flux, low neutron surplus etc.).
The Russians have a couple of fast sodium-cooled reactors, the BN-600 and BN-800 which produce power, breed new fuel and burn waste but they are still very much beta-level designs. They might be useful in another fifty or sixty years when mined uranium becomes more expensive.
LOX/LH2 motors have a good enough Isp figure that they can take the hit in performance -- the Vulcain 2 runs between about 360 at sea level and 420-odd in vacuum, comfortably outperforming vacuum-specific kerosene/LOX designs at all altitudes. The SpaceX Merlins are actually quite poor performers for kerosene/LOX but there may be other trade-offs in terms of construction costs and reusability. They can certainly do the job of getting modest amounts of materiel into orbit.
As for the Raptor engine I'll be interested to see where they go with it. Other people have tried methane/LOX in the past but reported problems. I've heard there is a fuel decomposition problem resulting in coking of the pumps as well as sulphur impurities in the methane causing problems too. What puzzles me is the mention of using a partially-cryogenic fuel mix as an interplanetary engine; LOX is not storable over any sort of a timescale even in space and even methane would require active refrigeration to stay liquid for weeks or months on end during a transfer orbit to, say, Mars.
There are a number of launchers that burn the same engines from ground to true vacuum, indeed the Shuttle's engines burned from launch to orbit insertion (aided by the SRBs in the early part of the flight). Other examples include the Vulcain-2 on the Ariane V and the RS-68A central core stage of the Delta 4 Heavy. Notably all these long-duration burn motors are LH2/LOX which have even better Isp numbers than kerosene/LOX motors.
A modernised version of the F-1 did exist, with much better Isp of 311 seconds at sea level and a greater thrust of 7.25MN at sea level. It could be throttled and pivoted, unlike the brute-force-and-ignorance of the fixed F-1. It's called the RD-171. It spawned a series of cut-down versions flying today such as the two-chamber Atlas RD-180 and the single-chamber Angara RD-191/Antares RD-151.
As for the Saturn V, the first stage spent 10% of its burn time and fuel just clearing the tower so vacuum performance was not really a mission-critical factor in the F-1's development and design. It was laid out in the early days of rocket development where "design" involved slide rules and large sheets of drafting parchment -- the idea of CAD, computer modelling, 3-D printing of engine parts, modern engineering materials etc. were science-fiction dreams whereas they had to bend metal then and there.
What is your evidence that there is no demand for large objects in orbit?
My evidence is that there is actually, in reality, no demand for large objects in orbit. I qualify this statement by saying there's no money being fronted up to buy heavy lift launches of large objects in the 50-tonne region other than the SLS project (which is itself an assembly of small-objects-to-orbit). Wishful thinking, paper exercises and want-to's don't count as a "demand".
I understand SpaceX has some people interested in buying launches of the Falcon Heavy but they're constellations of small satellites, not unitary vehicles. As far as I know nobody's yet cut a cheque for such a launch since the Falcon Heavy's initial proving flight is getting pushed further and further down the calendar due to circumstances.
It didn't need to be since it never ran in true vacuum. The F-1 was actually optimised for reliability and not-killing-the-passengers hence its abysmal performance by today's standards. Even the SpaceX Merlin 1-D has a better Isp figure than the F-1.
If Spacex could lift 200mT to LEO for costs that are comparable to today's heavy launches, would new uses arise?
Such as? The only unitary large-lift mission I can think of is a single-mirror super-Hubble space observatory which has its own problems -- building a one-piece very large mirror, say five metres in diameter that could survive 3G-plus during launch, vibration etc. isn't going to be easy or light. The James Webb is using folding mirror segments and will have an effective diameter of 6.5 metres when deployed and it fits in a regular launcher fairing.
We've got better at doing things in space in the past fifty years, we don't have to go back into the Jet Age to justify Big Dumb Boosters.
As an aside, large amounts of stuff needed in orbit is actually fuel for satellite manoeuvering, deep-space probes, a future manned return to the Moon etc. A remarkable amount of the mass delivered into LEO and GEO today is cheap fuel at a delivery cost of $5000/kg. What I'd like to see Musk doing is working on a robot fuel production system based on, say, Ceres or other water and carbon rich asteroids, bringing back tankers full of fuel to Earth orbit. That way he could go to Mars without having to lift a thousand tonnes of fuel up from the ground in expensive boosters.
Sure there's an interest in big launches, big-mirror observatories and the like. What there isn't are the bucks to pay for them and the need for multiple launches a year that would justify spending tens of billions to develop a 50-tonne class launcher which would only fly once a year, if that.
At the moment humanity is launching about ten to twelve vehicles a month -- December 2015 was a recent activity peak with eighteen launches, three of them within the same 24-hour period. The next large scientific payload I know of is the James Webb telescope which will fly on an Ariane V in 2018, and that's only 6.6 tonnes.
ESA are blowing the cobwebs off their own heavy-lifter, the ES variant of the Ariane V for a couple of missions to launch four Galileo satellites at a time but apart from its original purpose to fly the ATV resupply vehicles to the ISS nobody needing a 20-tonne unitary lift has been buying flights on it, while the regular ECA variant of Ariane (10 tonnes to GTO, usually two GEO satellites plus SYLDA carrier) and the smaller Vega have full order books.
this would still be a major item on the list of things you need to do in order to hurl big stuff into Earth's orbit more affordably. There are long waiting lists of customers for such capability.
There isn't a large pent-up demand for "big stuff" in orbit, at least nothing that anyone's willing to pay even $5000/kg for. The demand for launches of up to fifteen tonnes a lump is handled by the current fleet of rockets. Very occasionally the US spy industry wants to put a unitary big-mirror observation satellite up and that can run to 20-25 tonnes. In those cases the Delta Heavy is used, the only time it is ever launched as far as I know.
The human race has got very good at throwing up small lumps of stuff into orbit and putting them together there afterwards -- the ISS is over 400 tonnes of small lumps, none of them over ten tonnes in mass when they were on the ground. A heavy lifter is not really needed for day-to-day operations or even a blue-sky Manned Mars mission, it's achievable with today's hardware and without the cost overheads of developing new heavy launchers with little or no other commercial sales to pay for them.
this is a portable aircraft with a good carry capacity.
The new version of the Russian Mi-26 heavy-lift helicopter can, reportedly, lift 25 tonnes, significantly more than the Airlander. Existing models of the Mi-26 can carry 20 tonnes of cargo, land on large ships, don't need lots of prepared ground to operate from etc. There's talk of an evolutionary new version to be developed jointly by Russia and China which would be able to lift 33 tonnes but it's still on the drawing board.
The Airlander folks have glossy brochures extolling later development versions of their airship which reputedly would be able to carry up to 60 tonnes of cargo but it's taken them all this time to get their first prototype into the air. I wouldn't hold my breath waiting for that larger version to make its first flight.
Yes, longer-wavelength radars can indeed detect stealthy aircraft. Warships with sea-sweeping radars can often spot such aircraft. The problem is they can't hand off an accurate location and track to the anti-aircraft missile radars which need to be much higher frequency to determine the aircraft's position to within a few centimetres so they can actually hit it. Those missile system radars are what the stealth profiles and skin coatings are designed to be near-invisible to and they do that job very well. At the same time active radars are a perfect target for anti-radar missiles of the sort the F-35 carries among other payloads. In addition it can network its own radar detection systems, handing off radar targets to other aircraft such as the F-14 which can't approach a defence area too closely because they would be detected and fired upon.
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So, for the US, reprocessing must not be economical or it would be happening already.
Freshly-mined uranium is cheap and plentiful and a once-through cycle of mining, enrichment and consumption is less expensive than fuel derived from current spent fuel reprocessing systems, in part because they are based on military-style weapons-grade plutonium production (the PUREX process) since that was the first method developed to deal with spent fuel. There is some research going on into lower-cost and simpler spent fuel reprocessing but it's not a priority given the low cost of fresh uranium and yellowcake production at the moment.
France and other nations such as Russia, Britain and Japan reprocess spent fuel for other reasons -- it vastly reduces the volume of material needing to be stored for long periods of time, for one thing. The Russians are working on advanced fuel cycles to burn spent fuel in fast reactors like the BN-800. Japanese have a breakout capability to make nuclear weapons if they decide to -- The Monju breeder, the reprocessing plant at Rokkaisho and they even have the small Epsilon orbital launcher to repurpose as an ICBM if they choose.
Accuracy per se isn't the real advantage of adding Galileo to the existing Navstar and Glonass global positioning satellite networks since better fix data is more dependent on correction overlay services like WAAS in the US and EGNOS in Europe, using fixed ground stations to provide extra accuracy information to GPS receivers allowing, for example, safe automatic landing of aircraft and shipping movements through restricted waters.
The main benefit of having a lot more GPS satellites in orbit is in places such as cities and mountainous regions where the skyview is restricted and it is possible to lose simultaneous line-of-sight to the four satellites required for a correct position/altitude/velocity result. More satellites means fewer blackouts for a given receiver in such situations.
Technically, a uranium tamper is still fissioned with fast neutron flux
Not quite. Uranium-238, the main component of depleted and also naturally occurring uranium doesn't fission. It WILL breed up into Pu-239 through neutron capture via an intermediate product and that will fission and produce energy if hit by neutrons.
Natural uranium has about 0.6% U-235 which will fission so it's a better tamper than depleted uranium which is usually about 0.2%-0.3% or so, providing more bang for your buck as it only takes one neutron to cause an atom of U-235 to fission whereas the U-238->Pu-239 breeding and fission process requires two neutrons. This all has to happen in a short period of time, too before the expanding bubble of fissionable material gets too large.
Jobs hated holes in his Precious. There are few holes in the current generation of Apple hardware. Jobs adored slim, the new laptops and phones are slimmer than ever. The legacy is being carried on all too well, with a dead man at the helm.
ESA have already put two space observatories, the Herschel infrared telescope and the Planck cosmic microwave background telescope into the L2 location. The JWT is being launched and deployed by ESA so it's not an absolute first for them.
ESA is paying for the launch and that entitles European scientists access to the instrument and data collected by it.
ESA is going to launch it, seriously.
It's going up on an Ariane V launcher using a French-derived LOX/LH2 engine and Italian solid-rocket boosters with a lot of German sparkly bits to do the control.
Saying "the French" is like saying NASA = "Floridans".
And those forward operating bases need to be protected from enemy raids so adding hundreds of troops, vehicles, fuel, logistics etc. to the front lines. The backfield bases operating planes like the F-15SE are usually already in place in friendly territory or on carriers and they can do the same job or better than the A-10 without the frontline logistical load.
Basically the A-10 is an older weapons system in a world which has moved forward. The F-35 is a sniper picking off targets from beyond light AA range (MANPADs, heavy machine guns and rapid-fire cannon) while the A-10 conducts hand-to-hand combat with the enemy if it tries to use its Big Stupid Gun. It's not like it can fly without the BSG either, the entire airframe is built around it. Other aircraft can carry guns with similar capabilities in terms of rate of fire in conformal packs or underwing if the mission requires it but they don't HAVE to cart them around if they're not needed.
The A-10 is stiffy-inducing like battleships. They're obsolete like battleships and a waste of manpower and effort like battleships. There are folks who think battleships should be in the armoury today, for no real reason other than the stiffy they induce. The A-10 is a flying battleship, basically.
Dell's Precision series laptops configured with a Xeon CPU and 64GB ECC DRAM option are not targetted at gamers, they're portable workstations. Same with HP's ZBooks, up to 64GB RAM and NVidia Quadro graphics cards, not an option a gamer would usually choose.
They were built cheap to be flown by ANG pilots over West Germany to get shot down by self-propelled AA guns and short-range missiles deployed with Soviet spearpoint armour brigades. The Big Stupid Gun was designed to chew up personnel carriers and trucks and other targets of opportunity and maybe damage/kill tanks but to use it the pilot had to get within a kilometre or so of the opposition and then fly straight toward them, not a good thing to do against anyone who can shoot back en masse. Times have changed and now there are better CAS weapons in the toolchest -- Maverick, Brimstone etc. which can do this kind of work from tens of kilometres out from any short-range defensive weapon systems that can knock down an attacking aircraft. They need to be deployed by smart platforms like the F-35 although older-generation aircraft like the F-16 can act as ammo mules for them with the F-35's instrumentation and C3 capabilities taking over after launch. The A-10 is too dumb in terms of battlefield networking to be of much use even in this role and besides the single pilot is busy flying the aircraft.
As for fast WWII strike aircraft, the Mosquito and the Typhoon were in the same speed range as the A-10. The F-35, F-15SE and F-18 can be on station in half the time it takes to get an A-10 into position to do some good.
The A-10 needs a full-length runway to operate from unlike the carrier-based F-18 and the F-35. That means several kilometres of airfield perimeter to protect from raids by enemy forces which means lots of troops, logistics etc. A fast CAS/strike aircraft can operate from bases in safe ground far from the enemy and still get to operational areas in time to do some good if needed.
The A-10 isn't in production, the last airframe came off the production line in 1984, over thirty years ago.
There's a porky programme ongoing for Boeing to re-wing some of them since they're falling apart, having been built cheaply to fly and die over the West German countryside against Soviet armour and air defences in an all-out war. Luckily they've not had to face a real air defence network for the past ten years or so but even against the Iraqis severely degraded systems a bunch of them were lost in 2003.
A-10s are not actually very effective in the CAS role, being a single-seater where the pilot has to fly the plane in rough air close to the ground while also identifying targets and delivering fire. The number of blue-on-blue incidents listed against A-10s reflects this time-management problem. They also have to come within reach of ground-based anti-artillery guns to use their Big Stupid Gun rather than standing off and killing the enemy with ranged weapons. Before anyone points out how rugged they are ("titanium bathtub!") remember that significant damage is a mission kill, they have to get out if they get chewed up and leave the ground-pounders to their own devices.
A-10s are surprisingly slow (slower than some WWII strike/CAS piston-engined aircraft!) which means they have to operate from full-sized air bases close to the front line to provide a quick-response CAS capability which in turn require defence from attacks, supply, logistics etc. Any of the really capable CAS aircraft existing today and the future F-35 have speed and range on their side as well as carrier capability which is less logistically intensive. They aren't also sitting ducks in case they operate against anything more dangerous than Bushmen with spears.
The new MacBook Pro is slimmer than the Dell XPS. That's what's important. To Apple.
The Zorro mutli-touch digitiser sales pitch says:
Resolution : 32767 x 32767(interpolation), 109 x 61(Physical)
It's purely on-off touch with no pressure-sensitive stylus as the MS device has and which artists and creative types want and need. That's why the CintiQ 27" digitiser display costs $2800 even though its display resolution isn't nearly as good as the Surface device.
From the actual article -- "includes a 28" display with 13.5 million pixels at a 4500x3000 resolution"
The standard 4k resolution mentioned was a comparison, not part of the spec of the Surface. As for the price comparison, please add in the cost of a high-definition screen-based digitiser to the Apple iMac spec and get back to us. Oh, the iMacs don't have a built-in screen digitiser as an option? Oops.
...with the original article. If "the missile will weigh up to 10 tons" then it's not going to get very far laden down with "up to 10 tons of nuclear cargo".
Deary deary me. I suspect the translation service they used (Google Hackslate, perchance or Bing Ablator) got stuff very very wrong.
Looking at it without the hype the new missile is an upgraded version of an older design with similar capabilities. It's probably constrained to fit into existing land-based silos the same way the US Trident missile upgrades were. The MIRV payloads may be getting updated to ensure penetration of close-in missile defence systems like Standard and Patriot plus possibly a target-seeking option to allow for hitting a US CVBG on the high seas, and that extra capability may be why they're building something with more payload capability than the older SS-18. I'd expect them to reduce the total number of ready missiles as they decommission their older missiles though.
Thorium (Th-232) isn't fissile, it needs to be bred up into U-233 to produce energy. U-233 works quite well in a nuclear weapon core (the US fired off at least two test devices back in the day). The U-233 in a proposed thorium reactor is pure, it has no contaminants that make it difficult to weaponise by an unscrupupous operator.
There are very few commercial breeder reactors still around or in operation since mined uranium is cheap and plentiful and breeders generally have a poor operational record, something that does not bode well for any thorium reactor that might be built since they share a lot of the same engineering technology (very hot compact core, solid moderator, very high neutron flux, low neutron surplus etc.).
The Russians have a couple of fast sodium-cooled reactors, the BN-600 and BN-800 which produce power, breed new fuel and burn waste but they are still very much beta-level designs. They might be useful in another fifty or sixty years when mined uranium becomes more expensive.
LOX/LH2 motors have a good enough Isp figure that they can take the hit in performance -- the Vulcain 2 runs between about 360 at sea level and 420-odd in vacuum, comfortably outperforming vacuum-specific kerosene/LOX designs at all altitudes. The SpaceX Merlins are actually quite poor performers for kerosene/LOX but there may be other trade-offs in terms of construction costs and reusability. They can certainly do the job of getting modest amounts of materiel into orbit.
As for the Raptor engine I'll be interested to see where they go with it. Other people have tried methane/LOX in the past but reported problems. I've heard there is a fuel decomposition problem resulting in coking of the pumps as well as sulphur impurities in the methane causing problems too. What puzzles me is the mention of using a partially-cryogenic fuel mix as an interplanetary engine; LOX is not storable over any sort of a timescale even in space and even methane would require active refrigeration to stay liquid for weeks or months on end during a transfer orbit to, say, Mars.
There are a number of launchers that burn the same engines from ground to true vacuum, indeed the Shuttle's engines burned from launch to orbit insertion (aided by the SRBs in the early part of the flight). Other examples include the Vulcain-2 on the Ariane V and the RS-68A central core stage of the Delta 4 Heavy. Notably all these long-duration burn motors are LH2/LOX which have even better Isp numbers than kerosene/LOX motors.
A modernised version of the F-1 did exist, with much better Isp of 311 seconds at sea level and a greater thrust of 7.25MN at sea level. It could be throttled and pivoted, unlike the brute-force-and-ignorance of the fixed F-1. It's called the RD-171. It spawned a series of cut-down versions flying today such as the two-chamber Atlas RD-180 and the single-chamber Angara RD-191/Antares RD-151.
As for the Saturn V, the first stage spent 10% of its burn time and fuel just clearing the tower so vacuum performance was not really a mission-critical factor in the F-1's development and design. It was laid out in the early days of rocket development where "design" involved slide rules and large sheets of drafting parchment -- the idea of CAD, computer modelling, 3-D printing of engine parts, modern engineering materials etc. were science-fiction dreams whereas they had to bend metal then and there.
What is your evidence that there is no demand for large objects in orbit?
My evidence is that there is actually, in reality, no demand for large objects in orbit. I qualify this statement by saying there's no money being fronted up to buy heavy lift launches of large objects in the 50-tonne region other than the SLS project (which is itself an assembly of small-objects-to-orbit). Wishful thinking, paper exercises and want-to's don't count as a "demand".
I understand SpaceX has some people interested in buying launches of the Falcon Heavy but they're constellations of small satellites, not unitary vehicles. As far as I know nobody's yet cut a cheque for such a launch since the Falcon Heavy's initial proving flight is getting pushed further and further down the calendar due to circumstances.
It didn't need to be since it never ran in true vacuum. The F-1 was actually optimised for reliability and not-killing-the-passengers hence its abysmal performance by today's standards. Even the SpaceX Merlin 1-D has a better Isp figure than the F-1.
F-1 - Isp (sea level) = 263 seconds.
Merlin 1-D Isp (sea level) = 282 seconds.
RD-180 Isp (sea level) = 311 seconds.
If Spacex could lift 200mT to LEO for costs that are comparable to today's heavy launches, would new uses arise?
Such as? The only unitary large-lift mission I can think of is a single-mirror super-Hubble space observatory which has its own problems -- building a one-piece very large mirror, say five metres in diameter that could survive 3G-plus during launch, vibration etc. isn't going to be easy or light. The James Webb is using folding mirror segments and will have an effective diameter of 6.5 metres when deployed and it fits in a regular launcher fairing.
We've got better at doing things in space in the past fifty years, we don't have to go back into the Jet Age to justify Big Dumb Boosters.
As an aside, large amounts of stuff needed in orbit is actually fuel for satellite manoeuvering, deep-space probes, a future manned return to the Moon etc. A remarkable amount of the mass delivered into LEO and GEO today is cheap fuel at a delivery cost of $5000/kg. What I'd like to see Musk doing is working on a robot fuel production system based on, say, Ceres or other water and carbon rich asteroids, bringing back tankers full of fuel to Earth orbit. That way he could go to Mars without having to lift a thousand tonnes of fuel up from the ground in expensive boosters.
Sure there's an interest in big launches, big-mirror observatories and the like. What there isn't are the bucks to pay for them and the need for multiple launches a year that would justify spending tens of billions to develop a 50-tonne class launcher which would only fly once a year, if that.
At the moment humanity is launching about ten to twelve vehicles a month -- December 2015 was a recent activity peak with eighteen launches, three of them within the same 24-hour period. The next large scientific payload I know of is the James Webb telescope which will fly on an Ariane V in 2018, and that's only 6.6 tonnes.
ESA are blowing the cobwebs off their own heavy-lifter, the ES variant of the Ariane V for a couple of missions to launch four Galileo satellites at a time but apart from its original purpose to fly the ATV resupply vehicles to the ISS nobody needing a 20-tonne unitary lift has been buying flights on it, while the regular ECA variant of Ariane (10 tonnes to GTO, usually two GEO satellites plus SYLDA carrier) and the smaller Vega have full order books.
this would still be a major item on the list of things you need to do in order to hurl big stuff into Earth's orbit more affordably. There are long waiting lists of customers for such capability.
There isn't a large pent-up demand for "big stuff" in orbit, at least nothing that anyone's willing to pay even $5000/kg for. The demand for launches of up to fifteen tonnes a lump is handled by the current fleet of rockets. Very occasionally the US spy industry wants to put a unitary big-mirror observation satellite up and that can run to 20-25 tonnes. In those cases the Delta Heavy is used, the only time it is ever launched as far as I know.
The human race has got very good at throwing up small lumps of stuff into orbit and putting them together there afterwards -- the ISS is over 400 tonnes of small lumps, none of them over ten tonnes in mass when they were on the ground. A heavy lifter is not really needed for day-to-day operations or even a blue-sky Manned Mars mission, it's achievable with today's hardware and without the cost overheads of developing new heavy launchers with little or no other commercial sales to pay for them.
this is a portable aircraft with a good carry capacity.
The new version of the Russian Mi-26 heavy-lift helicopter can, reportedly, lift 25 tonnes, significantly more than the Airlander. Existing models of the Mi-26 can carry 20 tonnes of cargo, land on large ships, don't need lots of prepared ground to operate from etc. There's talk of an evolutionary new version to be developed jointly by Russia and China which would be able to lift 33 tonnes but it's still on the drawing board.
The Airlander folks have glossy brochures extolling later development versions of their airship which reputedly would be able to carry up to 60 tonnes of cargo but it's taken them all this time to get their first prototype into the air. I wouldn't hold my breath waiting for that larger version to make its first flight.
Yes, longer-wavelength radars can indeed detect stealthy aircraft. Warships with sea-sweeping radars can often spot such aircraft. The problem is they can't hand off an accurate location and track to the anti-aircraft missile radars which need to be much higher frequency to determine the aircraft's position to within a few centimetres so they can actually hit it. Those missile system radars are what the stealth profiles and skin coatings are designed to be near-invisible to and they do that job very well. At the same time active radars are a perfect target for anti-radar missiles of the sort the F-35 carries among other payloads. In addition it can network its own radar detection systems, handing off radar targets to other aircraft such as the F-14 which can't approach a defence area too closely because they would be detected and fired upon.