It'd probably be more practical to set up D-T fusion helium-3 factories on the moon, for that matter. Not that it'd be a good idea, just not quite as bad of one as strip mining a hundred thousand square kilometers of the lunar surface per year for it.
And when reactors get to the point where they can make use of aneutronic reactions, there are aneutronic reactions that don't require helium-3. Which do you pick, the most abundant isotope of boron, or the least abundant isotope of helium? Oh, and the easily achievable reactions involving the latter aren't actually fully aneutronic.
Even if you ignore that and press ahead with helium-3...by the time we get there, we'll have been operating D-T reactors for some time, and keeping stockpiles of tritium, which produces a constant stream of helium-3 as it decays.
Nobody's bothered developing a power reactor that uses 3He because we haven't even gotten the much easier D-T reactions usable for such things yet.
Nobody *will* bother developing a power reactor that uses 3He because p-11B fusion is just as good (better actually, the more feasible 3He reactions involve side reactions that produce neutrons) and doesn't require processing 2 billion+ tons of lunar regolith every year.
...no. There's no modules, no assembly in orbit, only refueling. The transits would average 115 days, but could be made much shorter at a cost in payload. BFR does not use minimum-energy transits, it starts out with 6+ km/s of delta-v in LEO when carrying its maximum launch payload of 150 t, and is burdened with far less payload when it starts off with the same propellant load from the surface of Mars. There's huge amounts of information available about the BFR system, go look.
The plan is not to come back after half a year on Mars. SpaceX isn't talking about a flags-and-footprints mission, they are talking about staging around 600 t of supplies on the surface with 4 cargo craft before sending 2 craft with their own heavy loads of supplies and minimal crews to set up a propellant plant on Mars. For those who do wish to come back right away, 2 ~4 month transits separated by a short stay on Mars are not equivalent to 2 years in solar orbit in terms of either gravity or radiation exposure and do not require artificial gravity or radiation shielding/life support capabilities beyond what we already have.
Trips to Mars don't take two years. SpaceX's Mars plans involve transit times of 3-4 months. You don't need artificial gravity for that, and it is well within what can be done with prepackaged food. A shorter trip also greatly reduces the amount of radiation shielding required.
You do need something a lot bigger than Dragon, which is why BFS has a payload capacity of 150 metric tons and would only start to carry humans to Mars after several unmanned spacecraft had already landed with supplies. It also will have toilets, something that Dragon lacks, which I suspect is something those tourists will be happy to delay their trip a few years in order to have.
For that matter, the atmosphere of Mars alone is a good equivalent for Earth's magnetic field, giving a human naked on the surface better radiation shielding than someone on the ISS:
Obviously, someone naked on the surface would have a short life expectancy for other reasons, but the same is true of most of the Earth's surface. There are only a few locations where humans can survive without technological assistance. The idea that we are somehow so super-specialized for Earth that we can't possibly survive elsewhere is simply not realistic, and in fact is contradicted by the fact that humans were able to travel to and walk on the moon just 12 years after they first managed to lob something into orbit.
Oof. I thought that unit cost for Skylon was unrealistically high. Turns out it's from a Reaction Engines paper published at IAC 2014, which assumed a 5 billion Euro subsidy for 50 vehicles. It's actually one of the lower numbers in the paper. Others:
~$11 B in airframe development cost ~$6 B in engine development cost ~$700 M in upper stage development cost ~$1.3-2.1 B per spaceport
By then, Blue Origin might have evolved New Glenn into a fully-reusable system that can compete with BFR for smaller payloads. Of course, they have to actually reach orbit first.
Those pesky facts: Reaction Engines got £60 million, about $80 million, to develop a test engine to demonstrate the basic propulsion cycle. That does not get Skylon anywhere close to flight hardware. The first test flights are roughly 7 years into the future, should someone decide to pour another $10 billion dollars (closer to $12 billion really) into development, at which point Skylon's launch costs will be an order of magnitude higher than BFR's. Good luck getting those billions.
The SSTO Skylon being discussed today is totally irrelevant to SpaceX. A staged vehicle might be viable, but air breathing is fundamentally a much more complicated approach for very little gain, and is unlikely to translate to any cost advantage.
Falcon 9/Heavy has already achieved most of Skylon's cost reductions without requiring $10 billion to develop, and can improve further if fairing reuse works out. Worse, BFR is expected to achieve around the same recurring cost per flight as Skylon while having the ability to deliver 9 times as much payload, and also being able to use in orbit refueling to deliver the full payload to higher orbits without using an expendable upper stage. And BFR doesn't require any revolutionary new technologies, making it much more likely to actually hit those cost targets, and will be flying much sooner even with delays.
If they can turn Skylon into a staged vehicle, they might be able to compete, but still won't be pressuring SpaceX like they are doing to the competition now.
"the heating of water from GCR or solar radiation is utterly irrelevant"
Neutron capture is nearly so, as there's no cosmic or solar neutrons to capture. Solar radiation and cosmic rays are composed of charged particle radiation and EM. Only GCRs are capable of inducing radioactivity, and that's by spallation, not neutron capture. The only free neutrons are those produced by spallation, and the contribution is minor.
Your primary concern is bremsstrahlung, electromagnetic secondary radiation, which can be significant from solar protons and electrons striking high-z materials. Water's pretty good at blocking charged particles while limiting bremsstrahlung, as are things like polyethylene.
That's completely backwards. Being able to electronically form and steer the beam without any physically moving components makes phased arrays particularly well suited to applications where the array is mobile, which is why they're used so widely on aircraft and ships, and they are already being incorporated into cell phones.
Another thing to consider is that not all of SpaceX's customers have to be on the ground, accessing the network through those terminals. Starlink could provide broadband internet connectivity to any satellite in LEO with a compatible optical link. For example, Iridium could launch a few of their own satellites with Starlink transceivers and get a massively redundant internet connection without any additional groundside hardware of their own.
And with multiple transceivers per Starlink satellite and a guaranteed stream of production for replacement satellites, the cost of those transceivers will be relatively low. Many small satellites might use a single optical transceiver as their only communications link, no ground infrastructure required.
...the whole point of the system is to provide distributed access, with terminals in offices, schools, residential areas, ships and aircraft, etc. Your data is not going through Denver.
For that matter, the second stage itself is more massive than the Roadster. He could have replaced the Roadster with a block of ice that would sublime in orbit, and the debris hazard would be essentially unchanged. It'd just have complicated the launch and left us a bit poorer culturally speaking.
The name of the next ASDS is the perfect response to those innumerate, ignorant, arrogant jackasses who think there was something wrong with Musk launching his old car as a test payload.
Space junk in low and geosynchronous Earth orbit is a problem, this is in solar orbit along with about a billion rocks of comparable mass. And the low cost/mass lift provided by rockets like the Heavy is going to be critical for tug operations to keep crowded Earth orbits clear. The Heavy launch has great implications for space debris, but as something to enable us to mitigate it, not as something that contributes to it.
The target orbit was one that went at least to Mars orbit. There were no requirements that it only go to Mars orbit. They burned to depletion to demonstrate the amount of second stage performance available after a 6 hour coast (that being a requirement of some defense launches).
It's a minuscule amount of the booster's mass, and mass is less important on the first stage anyway, but it's also a volatile fluid that spontaneously ignites on contact with air. You have more reasons than mass to want to minimize the quantities you're working with, especially when working with experimental hardware where things may go wrong.
Easier to install or pull for repair/replacement, too. And spreading the thrust out makes for a more efficient structure...this was the reason for the shift to the "octaweb" arrangement from the original "tic tac toe" grid, and mass optimization was stated as the reason for the large number of engines on the ITS (original, larger BFR...it didn't have 42 engines due to a need for redundancy, it was because it worked out better in mass optimization).
There's also the possibility of doing testing on subsets of the engines.
"TEA-TEB is pretty nasty stuff, it spontaneously combusts in the presence of oxygen."
Including that in the air. It's pretty clear why they don't want more of it aboard than they need.
It's possible it was a procedural fault, only equipping it with enough for a no-boostback landing, or that damage during the higher-speed reentry caused the outboard engines to leak it. (Which would be a problem they've already been working on...one of the major features of the upcoming Block 5 is significantly improved thermal protection.)
They didn't lose the blueprints, they have them archived. The problem is that they're on huge poorly-organized piles of microfilm and paper, not in modern CAD files, they specify parts and materials that haven't been produced in half a century, obsolete manufacturing processes that nobody left knows the details of, using manufacturing equipment that was scrapped or repurposed decades ago, and of the people who knew the thousands of little unspecified details about how to go from blueprint to working product, those who aren't dead are long retired.
The Saturn V is not manufacturable today, and it's not due to "missing blueprints", it's just hopelessly obsolete. Recreating it would involve almost completely redesigning it to be built with modern techniques, and the result would not be competitive with a modern ground-up design.
Polyethylene would provide better shielding for its mass, which is why it's good for spacecraft, but mass isn't that big of an issue for surface habitats. You actually want a lot of mass on your pressurized structures to help hold the roof down against internal pressure.
Maybe as a very short term shelter, but look into some of the Project Iceworm experiments done with digging military bases into Greenland glaciers. Ice isn't stable enough for that sort of thing, especially when being warmed by a base carved into it.
You might use water as shielding on the surface...fill plastic bags, stack them up over a supporting structure, let them freeze...but you'd probably be better off with sandbags.
No, you don't, because the majority of the cost is due to orbital mechanics. Asteroids tend to be in elliptical, high-inclination orbits, and those likely to contain significant volatiles are out in the main belt or further. Ceres, for example, would be a much more difficult colonization target than Mars (though potentially easier if you could refuel at Mars). With its extremely high propellant efficiency, low thrust ion thrusters giving it around 10 km/s of delta-v, the Dawn mission was only able to visit two asteroids, and it took years to get between them.
A gravity well can actually be a benefit. You don't have to perfectly match velocity with Mars to go into orbit around it. Stop a couple km/s short, and you can end up in the same orbit around Mars as Phobos, making Phobos easier to reach than it would be if Mars wasn't there. The Martian moons are some of the most accessible asteroid-like bodies specifically because of the gravity well of Mars. And then there's the propulsive advantages of doing your burns in a gravity well, due to the Oberth effect.
Slashdot Mirror
It'd probably be more practical to set up D-T fusion helium-3 factories on the moon, for that matter. Not that it'd be a good idea, just not quite as bad of one as strip mining a hundred thousand square kilometers of the lunar surface per year for it.
And when reactors get to the point where they can make use of aneutronic reactions, there are aneutronic reactions that don't require helium-3. Which do you pick, the most abundant isotope of boron, or the least abundant isotope of helium? Oh, and the easily achievable reactions involving the latter aren't actually fully aneutronic.
Even if you ignore that and press ahead with helium-3...by the time we get there, we'll have been operating D-T reactors for some time, and keeping stockpiles of tritium, which produces a constant stream of helium-3 as it decays.
Nobody's bothered developing a power reactor that uses 3He because we haven't even gotten the much easier D-T reactions usable for such things yet.
Nobody *will* bother developing a power reactor that uses 3He because p-11B fusion is just as good (better actually, the more feasible 3He reactions involve side reactions that produce neutrons) and doesn't require processing 2 billion+ tons of lunar regolith every year.
...no. There's no modules, no assembly in orbit, only refueling. The transits would average 115 days, but could be made much shorter at a cost in payload. BFR does not use minimum-energy transits, it starts out with 6+ km/s of delta-v in LEO when carrying its maximum launch payload of 150 t, and is burdened with far less payload when it starts off with the same propellant load from the surface of Mars. There's huge amounts of information available about the BFR system, go look.
The plan is not to come back after half a year on Mars. SpaceX isn't talking about a flags-and-footprints mission, they are talking about staging around 600 t of supplies on the surface with 4 cargo craft before sending 2 craft with their own heavy loads of supplies and minimal crews to set up a propellant plant on Mars. For those who do wish to come back right away, 2 ~4 month transits separated by a short stay on Mars are not equivalent to 2 years in solar orbit in terms of either gravity or radiation exposure and do not require artificial gravity or radiation shielding/life support capabilities beyond what we already have.
Trips to Mars don't take two years. SpaceX's Mars plans involve transit times of 3-4 months. You don't need artificial gravity for that, and it is well within what can be done with prepackaged food. A shorter trip also greatly reduces the amount of radiation shielding required.
You do need something a lot bigger than Dragon, which is why BFS has a payload capacity of 150 metric tons and would only start to carry humans to Mars after several unmanned spacecraft had already landed with supplies. It also will have toilets, something that Dragon lacks, which I suspect is something those tourists will be happy to delay their trip a few years in order to have.
For that matter, the atmosphere of Mars alone is a good equivalent for Earth's magnetic field, giving a human naked on the surface better radiation shielding than someone on the ISS:
https://www.jpl.nasa.gov/space...
Obviously, someone naked on the surface would have a short life expectancy for other reasons, but the same is true of most of the Earth's surface. There are only a few locations where humans can survive without technological assistance. The idea that we are somehow so super-specialized for Earth that we can't possibly survive elsewhere is simply not realistic, and in fact is contradicted by the fact that humans were able to travel to and walk on the moon just 12 years after they first managed to lob something into orbit.
Oof. I thought that unit cost for Skylon was unrealistically high. Turns out it's from a Reaction Engines paper published at IAC 2014, which assumed a 5 billion Euro subsidy for 50 vehicles. It's actually one of the lower numbers in the paper. Others:
~$11 B in airframe development cost
~$6 B in engine development cost
~$700 M in upper stage development cost
~$1.3-2.1 B per spaceport
PDF: https://forum.nasaspaceflight....
By then, Blue Origin might have evolved New Glenn into a fully-reusable system that can compete with BFR for smaller payloads. Of course, they have to actually reach orbit first.
Those pesky facts:
Reaction Engines got £60 million, about $80 million, to develop a test engine to demonstrate the basic propulsion cycle. That does not get Skylon anywhere close to flight hardware. The first test flights are roughly 7 years into the future, should someone decide to pour another $10 billion dollars (closer to $12 billion really) into development, at which point Skylon's launch costs will be an order of magnitude higher than BFR's. Good luck getting those billions.
The SSTO Skylon being discussed today is totally irrelevant to SpaceX. A staged vehicle might be viable, but air breathing is fundamentally a much more complicated approach for very little gain, and is unlikely to translate to any cost advantage.
Falcon 9/Heavy has already achieved most of Skylon's cost reductions without requiring $10 billion to develop, and can improve further if fairing reuse works out. Worse, BFR is expected to achieve around the same recurring cost per flight as Skylon while having the ability to deliver 9 times as much payload, and also being able to use in orbit refueling to deliver the full payload to higher orbits without using an expendable upper stage. And BFR doesn't require any revolutionary new technologies, making it much more likely to actually hit those cost targets, and will be flying much sooner even with delays.
If they can turn Skylon into a staged vehicle, they might be able to compete, but still won't be pressuring SpaceX like they are doing to the competition now.
"the heating of water from GCR or solar radiation is utterly irrelevant"
Neutron capture is nearly so, as there's no cosmic or solar neutrons to capture. Solar radiation and cosmic rays are composed of charged particle radiation and EM. Only GCRs are capable of inducing radioactivity, and that's by spallation, not neutron capture. The only free neutrons are those produced by spallation, and the contribution is minor.
Your primary concern is bremsstrahlung, electromagnetic secondary radiation, which can be significant from solar protons and electrons striking high-z materials. Water's pretty good at blocking charged particles while limiting bremsstrahlung, as are things like polyethylene.
That's completely backwards. Being able to electronically form and steer the beam without any physically moving components makes phased arrays particularly well suited to applications where the array is mobile, which is why they're used so widely on aircraft and ships, and they are already being incorporated into cell phones.
Another thing to consider is that not all of SpaceX's customers have to be on the ground, accessing the network through those terminals. Starlink could provide broadband internet connectivity to any satellite in LEO with a compatible optical link. For example, Iridium could launch a few of their own satellites with Starlink transceivers and get a massively redundant internet connection without any additional groundside hardware of their own.
And with multiple transceivers per Starlink satellite and a guaranteed stream of production for replacement satellites, the cost of those transceivers will be relatively low. Many small satellites might use a single optical transceiver as their only communications link, no ground infrastructure required.
...the whole point of the system is to provide distributed access, with terminals in offices, schools, residential areas, ships and aircraft, etc. Your data is not going through Denver.
For that matter, the second stage itself is more massive than the Roadster. He could have replaced the Roadster with a block of ice that would sublime in orbit, and the debris hazard would be essentially unchanged. It'd just have complicated the launch and left us a bit poorer culturally speaking.
The name of the next ASDS is the perfect response to those innumerate, ignorant, arrogant jackasses who think there was something wrong with Musk launching his old car as a test payload.
Space junk in low and geosynchronous Earth orbit is a problem, this is in solar orbit along with about a billion rocks of comparable mass. And the low cost/mass lift provided by rockets like the Heavy is going to be critical for tug operations to keep crowded Earth orbits clear. The Heavy launch has great implications for space debris, but as something to enable us to mitigate it, not as something that contributes to it.
The target orbit was one that went at least to Mars orbit. There were no requirements that it only go to Mars orbit. They burned to depletion to demonstrate the amount of second stage performance available after a 6 hour coast (that being a requirement of some defense launches).
It's a minuscule amount of the booster's mass, and mass is less important on the first stage anyway, but it's also a volatile fluid that spontaneously ignites on contact with air. You have more reasons than mass to want to minimize the quantities you're working with, especially when working with experimental hardware where things may go wrong.
Easier to install or pull for repair/replacement, too. And spreading the thrust out makes for a more efficient structure...this was the reason for the shift to the "octaweb" arrangement from the original "tic tac toe" grid, and mass optimization was stated as the reason for the large number of engines on the ITS (original, larger BFR...it didn't have 42 engines due to a need for redundancy, it was because it worked out better in mass optimization).
There's also the possibility of doing testing on subsets of the engines.
"TEA-TEB is pretty nasty stuff, it spontaneously combusts in the presence of oxygen."
Including that in the air. It's pretty clear why they don't want more of it aboard than they need.
It's possible it was a procedural fault, only equipping it with enough for a no-boostback landing, or that damage during the higher-speed reentry caused the outboard engines to leak it. (Which would be a problem they've already been working on...one of the major features of the upcoming Block 5 is significantly improved thermal protection.)
Yes, with major redesign work for modern materials and fabrication methods, including 3D printing.
They didn't lose the blueprints, they have them archived. The problem is that they're on huge poorly-organized piles of microfilm and paper, not in modern CAD files, they specify parts and materials that haven't been produced in half a century, obsolete manufacturing processes that nobody left knows the details of, using manufacturing equipment that was scrapped or repurposed decades ago, and of the people who knew the thousands of little unspecified details about how to go from blueprint to working product, those who aren't dead are long retired.
The Saturn V is not manufacturable today, and it's not due to "missing blueprints", it's just hopelessly obsolete. Recreating it would involve almost completely redesigning it to be built with modern techniques, and the result would not be competitive with a modern ground-up design.
Polyethylene would provide better shielding for its mass, which is why it's good for spacecraft, but mass isn't that big of an issue for surface habitats. You actually want a lot of mass on your pressurized structures to help hold the roof down against internal pressure.
Maybe as a very short term shelter, but look into some of the Project Iceworm experiments done with digging military bases into Greenland glaciers. Ice isn't stable enough for that sort of thing, especially when being warmed by a base carved into it.
You might use water as shielding on the surface...fill plastic bags, stack them up over a supporting structure, let them freeze...but you'd probably be better off with sandbags.
No, you don't, because the majority of the cost is due to orbital mechanics. Asteroids tend to be in elliptical, high-inclination orbits, and those likely to contain significant volatiles are out in the main belt or further. Ceres, for example, would be a much more difficult colonization target than Mars (though potentially easier if you could refuel at Mars). With its extremely high propellant efficiency, low thrust ion thrusters giving it around 10 km/s of delta-v, the Dawn mission was only able to visit two asteroids, and it took years to get between them.
A gravity well can actually be a benefit. You don't have to perfectly match velocity with Mars to go into orbit around it. Stop a couple km/s short, and you can end up in the same orbit around Mars as Phobos, making Phobos easier to reach than it would be if Mars wasn't there. The Martian moons are some of the most accessible asteroid-like bodies specifically because of the gravity well of Mars. And then there's the propulsive advantages of doing your burns in a gravity well, due to the Oberth effect.