For instance here is a great diagram from Mr Schutz's book :
which demonstrates beautifully the threshold aspect of kinetic energy to gain orbit. A mass is shot at a local horizontal from an elevated position ( atop a 300m tall tower ). The vertical axis in degrees is how far around the Earth did it go before it hit the ground ie. the rightmost point is 360 degrees aka a full circle and it will come back to the tower's top ( perfect world, no air resistance et al ). So it's pelting along at nearly 8 kilometers per second but a mere TWO meters per second makes all the difference. ! :-)
Cheers, Mike.
( edit ) I'm not Bezos bashing, but the clear message is that zero KE at 100km is an enormous gap yet to be spanned for LOE. Like say 200 GJ is missing .... :-)
( edit ) Specifically that is NOT another 200 GJ sitting in the tanks at the pad. It is 200 GJ plus : you have to lift the whole gadget including all the fuel that you burn higher up later on. Most fuel is there to lift other fuel .... and so on exponentially.
( edit ) I can't recall the exact figure, but if the Earth was just a few percent heavier ( or denser for that matter ie. smaller surface radius ) then no chemical fuel is currently known that would enable us to get to orbit at all via rocketry. I repeat : at all. The fuel energy density ( read : usable payload kinetic energy obtained from a given kilogram of propellants ) must be there with respect to the strength of the surface gravity.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
... SpaceX's Merlin 1D has power-to-weight in excess of 500 ...
Oooops. My BS. :-0
I read the specific impulse column not power-to-weight. A Merlin 1D is ~ 70% of the power-to-weight of a Saturn F-1 engine. The Merlin 1-D specific impulse is however ~ 30 % more than the F-1, but the comparison isn't legitimate because the F-1 wasn't used in ( much ) vacuum.
Cheers Mike.
( edit ) I should explain : specific impulse is how much thrust ( pushing force ) do you get per fuel consumption rate ( say kilograms burned per second ). To be exact that must depend on the fuels used. It is rather problematic/unusual to have a particular engine design capable of using multiple fuels. For instance H2/LOX yields a higher specific impulse than RP-1/LOX but H2 is much lower density than RP-1 ( remember that's high purity kerosene with relatively larger/massive hydrocarbon molecules compared to hydrogen dimer ) so for a given total energy expenditure H2 needs a much bigger tank. This is why the Shuttle's main tank ( the orange one which the two SRBs were attached either side to ) was huge. Also that's why turbo feed pumps are used. Total thrust at any given moment depends on the propellant delivery rate. No point sitting at the launch pad at a low flow rate. That's a stationary flame thrower a few seconds away from being a bomb. That's also why you want the engines to go from zero to hero real quick too ... they had a saying in the 50's & 60's : it is the first inch of the flight that matters the most. :-)
( edit ) Happy and SAFE New Year to all ! :-)
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
but if the Earth was just a few percent heavier ( or denser for that matter ie. smaller surface radius ) then no chemical fuel is currently known that would enable us to get to orbit at all via rocketry.
Grumble... I don't think so.
The Tsiolkovsky equation applied naively for a single-stage arrangement does suggest that as you work ever harder on getting the mass ratio (mass at burnout to mass at liftoff) down you'll not do any better than the specific impulse your engines give (which in turn is limited by the energy content of your fuel, as you mentioned) for that mass ratio, but the multi-stage trick is a way of pushing that mass ratio effectively far lower than the most optimistic managers might suppose the engineers could achieve.
The proof of the pudding is in the doing. Away back in 1972 Pioneer 10 left the near-Earth neighborhood heading toward the stars (i.e. beyond solar system escape velocity) courtesy of an additional solid rocket stage tacked on to the Atlas-Centaur primary launch vehicle. Wikipedia says it got up to 32,114 mph. While it does not mention the altitude at that moment, that is much above required velocity for Earth escape at any altitude. So we could have escaped a heavier earth.
Staging is a neat trick, but it gets really expensive really fast. A deeply depressing chapter in the draft Harvard high school physics text I got to read because my teacher was a check-reader gave a beautiful discussion of the prospects for interstellar flight by pointing out the stunning mass ratios you would need in order to get to a nearest star within a human lifetime using chemical rocket specific impulse. I don't remember specific examples, but think you would have needed something like a planetary mass at the start just to get the human to the other end, assuming the goal was to decelerate to a landing. Taking along food, clothing, shelter, and recreational reading not accounted for.
Of course the higher specific impulse reached by using a nuclear reactor helps a little, and the yet higher impulse of ion engines helps yet more. There is, however, the pesky problem of powering your ion engine--way out there where the sunlight is rather dim, which gets you right back to a nuclear reactor, and thus a terrible weight penalty for shielding.
Well staging always improves your outcome, but as you say diminishing returns drastically apply. But one approaches a limit from below. The basic assumptions of this proposal are pretty simple :
- there is an upper limit to energy density of chemical fuels.
- fuel available to burn at any given height/speed got there via the prior burning of other fuel.
So to the extent that both of these are true then Mr Exponential strikes the killer blow alas .... he can beat any polynomial sufficiently far out into the domain.
Sadly a more massive Earth, or starting deeper down the well, can increase the energy expenditure required to a degree exceeding the ability of chemicals to provide.
{ An implicit limit I failed to mention here is the materials available to contain the combustion. A higher temperature will give a higher exhaust velocity for a given choice of propellants and thus boost thrust. The Niobium alloys AFAIK are close to that optimum, and even that in the presence of cooling strategies which - yes, you guessed it - increase the mass to be carried at any moment the rocket is operating. I guess we may be thankful that the LOX serves two purposes here. Even the radiative cooling rate of the vacuum Merlin nozzles has an upper limit too. }
Cheers, Mike.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
Sadly a more massive Earth, or starting deeper down the well, can increase the energy expenditure required to a degree exceeding the ability of chemicals to provide.
Cheers, Mike.
Would there be any advantage in launching from, say, the top of Mt. McKinley, instead of just-barely-above-sea-level at Canaveral? (Not that I expect anyone in the government to even try to get that approved. But there must be some high-altitude spot in the world that no one gives much of a damn about.)
Pardon my near-total ignorance, but would it be at all feasible and advantageous to first launch a fuel tank into a parking orbit (or something?), then launch the payload and have it mate up with the fuel it needs for the escape from Earth orbit?
David
Miserable old git
Patiently waiting for the asteroid with my name on it.
Would there be any advantage in launching from, say, the top of Mt. McKinley, instead of just-barely-above-sea-level at Canaveral?
A big part of the advantage that would come from that would be avoiding some air drag in the early part of the ascent.
Now if you had a really tall mountain right at the equator which somehow had existing excellent heavy-duty roads to the top, just maybe you'd have something, but I've seen no serious proposals at all for the real Earth we have at hand.
But the thought of starting at several miles altitude rather than sea level is a major part of the appeal of several air launch systems.
Pegasus has been around for many years, and launches pretty small payloads for pretty low prices using an old L-1011 jet passenger transport as the "first stage".
Virgin Galactic is talking up LauncherOne--initially a scheme to launch somewhat bigger satellites than Pegasus using White Knight Two as the first stage, presumably on days off from lifting paying passengers in SpaceShipTwo for rides past the edge of space (but nowhere near orbit).
Apparently as they have talked to customers they have noticed a much bigger market for somewhat bigger payloads than that combination can handle, and Virgin Galactic has announced plans for an alternate higher-capacity launch vehicle in the form of a converted retired 747-400.
Finally, and by far most ambitiously, Paul Allen is funding Stratolaunch, at another size up the scale. In this scheme Scaled Composites (who else) is planned to start with two used 747-400 aircraft, re-using such things as engines and landing gear. and many systems, but with most of the primary airframe structure being new, to make the world's largest airplane as a dedicated first stage. Funny thing--though that first stage plan has not publicly changed, and remains under construction, the rocket they planned to use is no longer the plan of record and as of June 2015 the company said they were evaluating alternatives.
Stratolaunch has a nifty "dreaming by CGI" video up on youtube suggesting how this might look in airfield operations. Come to think of it, this video suggests they are NOT planning to use 747-400 landing gear trucks.
All of these schemes allow some savings in required impulse, a lower peak dynamic pressure during ascent, a more favorable (lower-angle) initial launch trajectory, and a considerable ability to "choose your weather" as a means to avoid weather delays. In principal, for payloads in the "sweet spot" for a given system, this approach should be rather cheaper than traditional means.
None of the schemes have yet become a significant factor in the world launch market, which is currently centered at mass/velocity points well above the capability of any of them. If SpaceX drives "traditional" launch costs down far enough, the window of opportunity for these folks may shrink below the event horizon.
Pardon my near-total ignorance, but would it be at all feasible and advantageous to first launch a fuel tank into a parking orbit (or something?), then launch the payload and have it mate up with the fuel it needs for the escape from Earth orbit?
You have to use & include solutions apart from pure chemical rocketry for sure. Certainly accumulating fuel in LOE - for a later big punch further upwards/away - is a reasonable one. To my way of thinking you have to get inventive, some examples come to mind :
- more utilisation of non chemical energy for station-keeping and orbit adjustments, once you've got up there. I can't recall how happy the results were after one Shuttle experiment, but driving a current through a suitably oriented long cable can do slow work to/from the Earth's magnetic field. Generate the electricity via solar arrays and get the geometry correct, then be patient.
- that cable cheat may enable one to try really cute ideas eg. use a cable system to keep a craft from descending ( due to drag ) while it skims through the very thin upper atmosphere. Then harvest water vapour that's there for H2/O2 .... :-)
- make the fuel up there. Going to the Moon is one option. We are now more confident of some water being there than in my youth. Split the water to H2 + O2. Chilling and liquefaction can really cost on Earth, but careful situation - out of the Sun believe it or not - and you can radiate heat from your fuel store into that lovely cold vacuum. Messy but do-able. Again you want to use the free energetic photon delivery service that our Sun provides gratis.
- leave the energy source on the ground. Lasers have been demonstrated to thrust objects up. A ruddy great rail gun - atop Mt Mckinley if you like - to just brute force ram stuff up there. Punting containers of fuel up would be an ideal payload for this : fluid has no structure to disrupt with massive accelerations.
I'll be mildly contentious too : tap expertise well out the usual fields that we draw knowledge and judgment from. We need cunning plans, offbeat thinking, and blindingly obvious answers that only six-year-olds can see. For example round up all those arrested for cheating in casinos for instance, give them a base course in what matters here, and then offer them money ( lots ) IF they get a really novel and workable plan that could be tested. Real engineers can do the actual work of sprucing things up ..... :-)
Cheers, Mike.
( edit ) Darn. You want to round up those that cheated at casinos but didn't get arrested. Yep. That would be the smarter group .... :-)
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
- more utilisation of non chemical energy for station-keeping and orbit adjustments, once you've got up there.
Ion thrusters for this purpose are no longer innovative, but well on their way to standard. The basic idea here is that you use electric power you get for "free" from solar panels to accelerate xenon atoms to several times faster velocity than any chemical reaction can generate in the exhaust, so the specific impulse is ball park an order of magnitude better. This directly means the expensive propellant mass you carry up to synchronous orbit does way more work, or lasts way longer, or you carry less, or ...
Traditionally these things have pretty paltry thrust, and really pitiful thrust to weight ratios, so have been used for station-keeping or for very long-duration burns on planetary missions (think weeks or months, not seconds or minutes), but rather recently if you read the right magazines you'll find advertisements boasting of "all-electric" satellites. In plain English this means (usually) satellites for geosynchronous orbit which forgo the standard chemical rocketry to finish the job of orbital finalization after the booster stage puts the assembly into a transfer orbit, and instead use ion thrust for this job.
Plus--a smaller spacecraft as the required xenon weighs a good deal less than the chemical rocket fuel it displaces.
Minus-as the thrust is relatively speaking still pretty tiny, it takes months longer to get to final, revenue-earning, orbit than the alternatives.
Not as "way out there" as the things Mike is hoping for, but happening in the real world.
Personally, I remember well the days when ion thruster thrusts were truly tiny and it did not look like a practical means of doing much of anything. So I'm seriously impressed the technology has gotten as far as it has. Not everything stopped with the end of Apollo, though sometimes it seems so.
Elon says recovered SpaceX vehicle ready to fly again, but this one won't. It will probably be put on display. Full article here. The steering paddles look pretty good, of course they are at the "top" of the stack.
There is an extra piece of evidence that SpaceX is at least doing some elements of the necessary preparatory work for a barge recovery of the January 17 Jason-3 launch first stage in the form of an application to the FCC for RF transmission involved.
This link covers permission to operate equipment to support an experimental recovery at two locations--the Vandenberg launch complex used by SpaceX and boat and a barge both located within ten miles of:
For instance here is a great
)
For instance here is a great diagram from Mr Schutz's book :
which demonstrates beautifully the threshold aspect of kinetic energy to gain orbit. A mass is shot at a local horizontal from an elevated position ( atop a 300m tall tower ). The vertical axis in degrees is how far around the Earth did it go before it hit the ground ie. the rightmost point is 360 degrees aka a full circle and it will come back to the tower's top ( perfect world, no air resistance et al ). So it's pelting along at nearly 8 kilometers per second but a mere TWO meters per second makes all the difference. ! :-)
Cheers, Mike.
( edit ) I'm not Bezos bashing, but the clear message is that zero KE at 100km is an enormous gap yet to be spanned for LOE. Like say 200 GJ is missing .... :-)
( edit ) Specifically that is NOT another 200 GJ sitting in the tanks at the pad. It is 200 GJ plus : you have to lift the whole gadget including all the fuel that you burn higher up later on. Most fuel is there to lift other fuel .... and so on exponentially.
( edit ) I can't recall the exact figure, but if the Earth was just a few percent heavier ( or denser for that matter ie. smaller surface radius ) then no chemical fuel is currently known that would enable us to get to orbit at all via rocketry. I repeat : at all. The fuel energy density ( read : usable payload kinetic energy obtained from a given kilogram of propellants ) must be there with respect to the strength of the surface gravity.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
RE: ... SpaceX's Merlin 1D
)
Oooops. My BS. :-0
I read the specific impulse column not power-to-weight. A Merlin 1D is ~ 70% of the power-to-weight of a Saturn F-1 engine. The Merlin 1-D specific impulse is however ~ 30 % more than the F-1, but the comparison isn't legitimate because the F-1 wasn't used in ( much ) vacuum.
Cheers Mike.
( edit ) I should explain : specific impulse is how much thrust ( pushing force ) do you get per fuel consumption rate ( say kilograms burned per second ). To be exact that must depend on the fuels used. It is rather problematic/unusual to have a particular engine design capable of using multiple fuels. For instance H2/LOX yields a higher specific impulse than RP-1/LOX but H2 is much lower density than RP-1 ( remember that's high purity kerosene with relatively larger/massive hydrocarbon molecules compared to hydrogen dimer ) so for a given total energy expenditure H2 needs a much bigger tank. This is why the Shuttle's main tank ( the orange one which the two SRBs were attached either side to ) was huge. Also that's why turbo feed pumps are used. Total thrust at any given moment depends on the propellant delivery rate. No point sitting at the launch pad at a low flow rate. That's a stationary flame thrower a few seconds away from being a bomb. That's also why you want the engines to go from zero to hero real quick too ... they had a saying in the 50's & 60's : it is the first inch of the flight that matters the most. :-)
( edit ) Happy and SAFE New Year to all ! :-)
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
RE: but if the Earth was
)
Grumble... I don't think so.
The Tsiolkovsky equation applied naively for a single-stage arrangement does suggest that as you work ever harder on getting the mass ratio (mass at burnout to mass at liftoff) down you'll not do any better than the specific impulse your engines give (which in turn is limited by the energy content of your fuel, as you mentioned) for that mass ratio, but the multi-stage trick is a way of pushing that mass ratio effectively far lower than the most optimistic managers might suppose the engineers could achieve.
The proof of the pudding is in the doing. Away back in 1972 Pioneer 10 left the near-Earth neighborhood heading toward the stars (i.e. beyond solar system escape velocity) courtesy of an additional solid rocket stage tacked on to the Atlas-Centaur primary launch vehicle. Wikipedia says it got up to 32,114 mph. While it does not mention the altitude at that moment, that is much above required velocity for Earth escape at any altitude. So we could have escaped a heavier earth.
Staging is a neat trick, but it gets really expensive really fast. A deeply depressing chapter in the draft Harvard high school physics text I got to read because my teacher was a check-reader gave a beautiful discussion of the prospects for interstellar flight by pointing out the stunning mass ratios you would need in order to get to a nearest star within a human lifetime using chemical rocket specific impulse. I don't remember specific examples, but think you would have needed something like a planetary mass at the start just to get the human to the other end, assuming the goal was to decelerate to a landing. Taking along food, clothing, shelter, and recreational reading not accounted for.
Of course the higher specific impulse reached by using a nuclear reactor helps a little, and the yet higher impulse of ion engines helps yet more. There is, however, the pesky problem of powering your ion engine--way out there where the sunlight is rather dim, which gets you right back to a nuclear reactor, and thus a terrible weight penalty for shielding.
Well staging always improves
)
Well staging always improves your outcome, but as you say diminishing returns drastically apply. But one approaches a limit from below. The basic assumptions of this proposal are pretty simple :
- there is an upper limit to energy density of chemical fuels.
- fuel available to burn at any given height/speed got there via the prior burning of other fuel.
So to the extent that both of these are true then Mr Exponential strikes the killer blow alas .... he can beat any polynomial sufficiently far out into the domain.
Sadly a more massive Earth, or starting deeper down the well, can increase the energy expenditure required to a degree exceeding the ability of chemicals to provide.
{ An implicit limit I failed to mention here is the materials available to contain the combustion. A higher temperature will give a higher exhaust velocity for a given choice of propellants and thus boost thrust. The Niobium alloys AFAIK are close to that optimum, and even that in the presence of cooling strategies which - yes, you guessed it - increase the mass to be carried at any moment the rocket is operating. I guess we may be thankful that the LOX serves two purposes here. Even the radiative cooling rate of the vacuum Merlin nozzles has an upper limit too. }
Cheers, Mike.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
RE: Sadly a more massive
)
Would there be any advantage in launching from, say, the top of Mt. McKinley, instead of just-barely-above-sea-level at Canaveral? (Not that I expect anyone in the government to even try to get that approved. But there must be some high-altitude spot in the world that no one gives much of a damn about.)
Pardon my near-total ignorance, but would it be at all feasible and advantageous to first launch a fuel tank into a parking orbit (or something?), then launch the payload and have it mate up with the fuel it needs for the escape from Earth orbit?
David
Miserable old git
Patiently waiting for the asteroid with my name on it.
RE: Would there be any
)
A big part of the advantage that would come from that would be avoiding some air drag in the early part of the ascent.
Now if you had a really tall mountain right at the equator which somehow had existing excellent heavy-duty roads to the top, just maybe you'd have something, but I've seen no serious proposals at all for the real Earth we have at hand.
But the thought of starting at several miles altitude rather than sea level is a major part of the appeal of several air launch systems.
Pegasus has been around for many years, and launches pretty small payloads for pretty low prices using an old L-1011 jet passenger transport as the "first stage".
Virgin Galactic is talking up LauncherOne--initially a scheme to launch somewhat bigger satellites than Pegasus using White Knight Two as the first stage, presumably on days off from lifting paying passengers in SpaceShipTwo for rides past the edge of space (but nowhere near orbit).
Apparently as they have talked to customers they have noticed a much bigger market for somewhat bigger payloads than that combination can handle, and Virgin Galactic has announced plans for an alternate higher-capacity launch vehicle in the form of a converted retired 747-400.
Finally, and by far most ambitiously, Paul Allen is funding Stratolaunch, at another size up the scale. In this scheme Scaled Composites (who else) is planned to start with two used 747-400 aircraft, re-using such things as engines and landing gear. and many systems, but with most of the primary airframe structure being new, to make the world's largest airplane as a dedicated first stage. Funny thing--though that first stage plan has not publicly changed, and remains under construction, the rocket they planned to use is no longer the plan of record and as of June 2015 the company said they were evaluating alternatives.
Stratolaunch has a nifty "dreaming by CGI" video up on youtube suggesting how this might look in airfield operations. Come to think of it, this video suggests they are NOT planning to use 747-400 landing gear trucks.
All of these schemes allow some savings in required impulse, a lower peak dynamic pressure during ascent, a more favorable (lower-angle) initial launch trajectory, and a considerable ability to "choose your weather" as a means to avoid weather delays. In principal, for payloads in the "sweet spot" for a given system, this approach should be rather cheaper than traditional means.
None of the schemes have yet become a significant factor in the world launch market, which is currently centered at mass/velocity points well above the capability of any of them. If SpaceX drives "traditional" launch costs down far enough, the window of opportunity for these folks may shrink below the event horizon.
RE: Pardon my near-total
)
You have to use & include solutions apart from pure chemical rocketry for sure. Certainly accumulating fuel in LOE - for a later big punch further upwards/away - is a reasonable one. To my way of thinking you have to get inventive, some examples come to mind :
- more utilisation of non chemical energy for station-keeping and orbit adjustments, once you've got up there. I can't recall how happy the results were after one Shuttle experiment, but driving a current through a suitably oriented long cable can do slow work to/from the Earth's magnetic field. Generate the electricity via solar arrays and get the geometry correct, then be patient.
- that cable cheat may enable one to try really cute ideas eg. use a cable system to keep a craft from descending ( due to drag ) while it skims through the very thin upper atmosphere. Then harvest water vapour that's there for H2/O2 .... :-)
- make the fuel up there. Going to the Moon is one option. We are now more confident of some water being there than in my youth. Split the water to H2 + O2. Chilling and liquefaction can really cost on Earth, but careful situation - out of the Sun believe it or not - and you can radiate heat from your fuel store into that lovely cold vacuum. Messy but do-able. Again you want to use the free energetic photon delivery service that our Sun provides gratis.
- leave the energy source on the ground. Lasers have been demonstrated to thrust objects up. A ruddy great rail gun - atop Mt Mckinley if you like - to just brute force ram stuff up there. Punting containers of fuel up would be an ideal payload for this : fluid has no structure to disrupt with massive accelerations.
I'll be mildly contentious too : tap expertise well out the usual fields that we draw knowledge and judgment from. We need cunning plans, offbeat thinking, and blindingly obvious answers that only six-year-olds can see. For example round up all those arrested for cheating in casinos for instance, give them a base course in what matters here, and then offer them money ( lots ) IF they get a really novel and workable plan that could be tested. Real engineers can do the actual work of sprucing things up ..... :-)
Cheers, Mike.
( edit ) Darn. You want to round up those that cheated at casinos but didn't get arrested. Yep. That would be the smarter group .... :-)
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
RE: - more utilisation of
)
Ion thrusters for this purpose are no longer innovative, but well on their way to standard. The basic idea here is that you use electric power you get for "free" from solar panels to accelerate xenon atoms to several times faster velocity than any chemical reaction can generate in the exhaust, so the specific impulse is ball park an order of magnitude better. This directly means the expensive propellant mass you carry up to synchronous orbit does way more work, or lasts way longer, or you carry less, or ...
Traditionally these things have pretty paltry thrust, and really pitiful thrust to weight ratios, so have been used for station-keeping or for very long-duration burns on planetary missions (think weeks or months, not seconds or minutes), but rather recently if you read the right magazines you'll find advertisements boasting of "all-electric" satellites. In plain English this means (usually) satellites for geosynchronous orbit which forgo the standard chemical rocketry to finish the job of orbital finalization after the booster stage puts the assembly into a transfer orbit, and instead use ion thrust for this job.
Plus--a smaller spacecraft as the required xenon weighs a good deal less than the chemical rocket fuel it displaces.
Minus-as the thrust is relatively speaking still pretty tiny, it takes months longer to get to final, revenue-earning, orbit than the alternatives.
Not as "way out there" as the things Mike is hoping for, but happening in the real world.
Personally, I remember well the days when ion thruster thrusts were truly tiny and it did not look like a practical means of doing much of anything. So I'm seriously impressed the technology has gotten as far as it has. Not everything stopped with the end of Apollo, though sometimes it seems so.
Elon says recovered SpaceX
)
Elon says recovered SpaceX vehicle ready to fly again, but this one won't. It will probably be put on display. Full article here. The steering paddles look pretty good, of course they are at the "top" of the stack.
There is an extra piece of
)
There is an extra piece of evidence that SpaceX is at least doing some elements of the necessary preparatory work for a barge recovery of the January 17 Jason-3 launch first stage in the form of an application to the FCC for RF transmission involved.
This link covers permission to operate equipment to support an experimental recovery at two locations--the Vandenberg launch complex used by SpaceX and boat and a barge both located within ten miles of:
North 32 7 44 West 120 46 43
I spotted this on the NASASpaceflight.com Jason 3 thread as previously posted.