Earth Launch with Lunar ‘Fuel’

guest blogger john hare

Earth launch for heavy vehicles currently involves lifting a lot of propellant to lift a lot less vehicle to lift even less payload. One of the frequent criticisms of suborbital flight is that it only uses a small fraction of the energy required to reach orbit. While that argument has some serious validity issues, it would be nice to be able to pop up a suborbital vehicle and hand off a payload to something else that took it to orbit. Mass ratio required would drop by a factor of 5. While it would be nice, it may be a while before some magic tech makes it possible.

Tethers are the frequent solution suggested for making this happen. Unfortunately current tech seems to be that your suborbital vehicle would need to be traveling at mach 15 or so to match velocities with a rotovator. While this will be a major breakthrough when it takes place, it still requires a serious performance vehicle to make the rendezvous. The suborbital vehicle for that mission will have to be fairly aggressively designed if it is a single stage. The mass ratio is about half that of an orbital vehicle with serious TPS still required. It will have to ride the tether around for a few orbits to get home, or land far enough down range that getting home is another logistics problem. As better tethers become available, these problems will slowly get better until a true beanstalk becomes possible.

I’m not aware of any other feasible technologies for doing the job of an advanced rotovator.

With airless aerobraking propulsion, there is a possible solution.  A chunk of lunar LOX launched into a near earth reentry trajectory will be at over 11 km/sec as it makes a near approach 100 miles up. If one pound of this impacted a suborbital pop up vehicle that had no significant horizontal velocity it would deliver an impulse equivalent to an Isp of 1,100+. If that pound vaporized and rebounded at random from a heat shield, it would deliver equivalent of another Isp of 550. So each pound of lunar volatiles would have an effective ‘Isp’ of 1,650 while the suborbital vehicle is motionless earth relative. As the vehicle gathered momentum, ‘Isp’ would drop as a linear function of less impact velocity of each succeeding LLOXball. By the time the suborbital vehicle was pushed to orbit, ‘Isp’ would be down to about 460 or so. Lunar regolith aerogel was suggested for the airless aerobraking. If feasible, that would solve several problems with the concept.

It works out to about 1.5 times as much LLOX as vehicle to make the push to orbit. A one ton upper stage with heat shield would need about one and one half tons of LLOX impact to push it to orbit. The size vehicle it would take to get that one ton inert upper stage into position is in dispute by the various people that build actual hardware. The old V2 would have used 4 tons of vehicle and 9 tons of propellant. There are at least a half a dozen credible newspace companies that believe they can beat that with a vehicle that flies daily or more. The list of less credible is somewhat more extensive. The list of companies that can place a ton in orbit without help is fairly long, and fairly expensive.

If a firm can just match the old tech and get an upper stage boost from the moon, then a ton to orbit will be considerably cheaper than is currently possible. This is a 14 ton earth GLOW and 1.5 lunar volatiles per ton to LEO. Heavy lift is the field that would make this pay. A modern expendable design for this purpose would have a mass ratio of about 2.5 and a dry mass of less than 10%. A 3,000 ton GLOW (Saturn5 class) would get 900 tons in orbit in one shot with help from 1,350 tons of lunar volatiles in intersect trajectory.

If it becomes desirable to get a lot of large payloads from the earth surface into space, this might be one path for doing it. If a suborbital craft can fly often, then it could launch large payloads once a day as it phased with the moon launched trajectory paths. It would be cheaper to use lunar raw material to facilitate earth launch than to manufacture finished components on the moon for the short term of a few decades. If SPS became economically desirable, this is a technique that could help make it possible to launch millions of tons of earth built products into orbit.

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johnhare

johnhare

I do construction for a living and aerospace as an occasional hobby. I am an inventor and a bit of an entrepreneur. I've been self employed since the 1980s and working in concrete since the 1970s. When I grow up, I want to work with rockets and spacecraft. I did a stupid rocket trick a few decades back and decided not to try another hot fire without adult supervision. Haven't located much of that as we are all big kids when working with our passions.
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21 Responses to Earth Launch with Lunar ‘Fuel’

  1. jsuros says:

    What a great idea. It can be applied to any of the general class of “sample return” missions where you have lots of cheap mass in orbit around a planet and are willing to trade it for bringing mass up from the surface cheaply.

    Trading mass from the ice moons of a gas giant for a big tank of He3 comes to mind, as well as mining Phobos to lift really heavy samples from Mars.

  2. john hare says:

    Jsuros,

    Are you suggesting using the martian moons to facilitate mars exploration and return?

  3. sjv says:

    Take a look at:

    http://www.walthelm.net/inverted-aerobraking/main.htm

    Which describes much the same idea. I found it while looking to see if there was a copy online of :

    Donald Kingsbury and Roger Arnold, The Spaceport, Analog Nov & Dec 1979

    They propose a “rail” several hundred km along a low earth orbit. A suborbital vehicle climbs to the rail, “lands” on the rail at high relative velocity, and the rail releases lunar oxygen progressively along its length, which is captured by a scoop on the suborbital vehicle, which “rebounds” the gas flow and expands it out a nozzle. More efficient of lunar oxygen than your proposal, possibly, but at the expense of considerable orbital infrastructure and a somewhat hair-raising “landing”.

    Later versions of the Leoport replace this with a mass driver type magnetic accelerator rail. Orbital momentum is transferred from the Leoport to the upward bound suborbital craft, and it maintained by incoming loads of lunar rock, some of which is then sent on to earth in returning sub-orbital vehicles.

    My recollections is that they later realized that keeping such a long rail “horizontal” along its orbit and straight would be extremely difficult or impossible. Functionally, it be like a tether, but not limited by material strength. But the mass and complexity would be considerable.

  4. jsuros says:

    I don’t know about return to Earth, but if you could mine volatiles from Phobos and launch them into a trajectory where they intersect with a vehicle that can raise itself up above most of the atmosphere of Mars, then you have a very easy way to move that vehicle into suborbital and/or orbital trajectories. It seems like a very good way to make multiple trips between Mars orbit and Mars surface with a minimum of ground infrastructure.

    Or in the simplest case, if you lug a ton of ice with you from earth and leave it in HEMO when you arrive, you could launch a sample return mission from a lander to just above the atmosphere, and airlessly aeroaccelerate it to orbit.

    It wouldn’t take much of a solid rocket to lift your sample return container up say 100 miles from the Martian surface, would it? Then aeroaccelerate it into orbit and have your return vehicle rendezvous and capture it.

  5. john hare says:

    Jsuros,

    I think you are seeing possibilities better than I am for this sort of thing. Reducing lift requirements from the surface to Martian orbit would definitely reduce cost of operations there. I’m starting to see your sample return point. Getting a NMO (Near Mars Object) to do what you suggested with eccentric HEO would be a gain.

    As far as I got was slowing an Earth grazing NEO to barely captured. I would prefer a 10,000 mile perigee to 100 on something large enough to do serious damage. Might also be a way to do large sample return from NEOs without rendezvous. Send an impactor first to blast off a chunk and start it moving along with the snowballs.

  6. jsuros says:

    I gave asteroid deflection some thought, actually. Here’s my idea. Send your LOXballs out to sling around Jupiter to reverse the direction of their orbit. On their return to the inner solar system, steer them into an intercept trajectory with an asteroid. Vaporize the LOXballs just before the collision and you have a cloud of gas closing at around twice the orbital velocity of the asteroid applying a whopper of an impulse uniformly across the entire surface area. Repeat as necessary until the asteroid is going where you want. With enough time to prepare this would probably deflect a dinosaur killer.

    I remember reading about a cold war scheme to mine Earth orbit by sending a “probe” full of plastic pellets to circle the moon and return on a anti-spin orbit. The idea was that you could release a cloud of pellets and sweep enemy satellites from the sky with very high energy collisions. After a few years the plastic pellets would dissolve in solar UV into pieces small enough to be pushed into decaying orbits by the solar wind. I’m glad the cold war is over. Anyway, my point is that though I don’t understand the math myself I’m pretty sure it would work.

    I like your NEO breakup and large scale “sample return” scheme. The only problem I see is that NEOs are the cheapest possible source of aeroacceleration volatiles. You run into a chicken and egg problem.

  7. Keith Henson says:

    There seems to be an approach described at the website to pop up 25 ton payload and 25 ton reaction mass laser stage to 250 miles and use a 4 GW laser to push it into GTO.

    This only makes sense for a traffic model in the billion kg/year range since the laser and redirection mirrors at GEO are about a 100 billion dollar investment. It does reduce the cost to around $10/kg for the lift from suborbital to GEO.

    This is a new proposal that originated within the last few months.

    Keith Henson

  8. john hare says:

    Sjv,

    Take a look at:

    http://www.walthelm.net/inverted-aerobraking/main.htm

    Which describes much the same idea. I found it while looking to see if there was a copy online of :

    When you go to that site, look in the upper right hand corner for an animation of Pulsed Inverted Aerobraking. Click on that and you get exactly what I was trying to say here except that they do it right.

    This will look like plagiarism poorly done on my part to any impartial observer. While it wasn’t, I certainly can’t prove that. What’s worse is that I used to read Analog, and have read stuff by Kingsbury. I don’t know for sure that I didn’t forget reading about the concept. This is embarrassing.

    Anybody interested in this concept should go to that site and check it out. They even have a way around the poor performance at low impact velocities, on board hydrogen plus impact oxygen for onboard Isp in the thousands.

    The only thing they seem to have missed was Jsuros idea of onboard pellets hitting the incoming LLOXballs for reliable vaporization. I included that suggestion in my apology email to the author and inventor of Pulsed Inverted Aerobraking, Dr. Walthelm.

  9. jsuros says:

    I had a sneaking suspicion the idea was too simple to be original. At least it’s only a couple of years old. Usually these brilliant schemes were thought of in the 1950’s…

    Dr. Walthelm’s idea of storing solar energy in heated lunar soil to continue operations over the long nights is very interesting. It gets around the “we have to build our bases at the poles” constraint that seems to have taken root in recent years.

  10. john hare says:

    Jsuros,

    I couldn’t find anything else by him on the net with a quick search. Could you point me to his solar storage info?

    Also you do have a contribution in the impact vaporization by small solid if it goes into service.

    I’m going to have to spend some time checking out prior art on these concepts when I go stray from the rocket tech.

  11. sjv says:

    This will look like plagiarism poorly done on my part to any impartial observer.

    But any experienced observer will know how common this sort of independent development is. Happens to me all the time.

    Don’t sweat it. Nothing to be embarrassed about at all. Take it as a sign that maybe your ideas aren’t all nuts.

  12. john hare says:

    Sjv,

    If possible, I would like to avoid the appearance as well as the reality of wrong doing. I intend to do business in this field sooner or later. If I reach that point, trust becomes an issue.

    There may be perfectly valid reasons to share a room with your secretary at the conference, and nothing wrong happened. That will be a cold comfort as you search for a new job while going through a divorce.

  13. jsuros says:

    John,

    I always check the higher level directories of links that interest me. Old habit. Dr. Walthelm’s thermal storage paper is here: http://www.walthelm.net/NightTimeEnergyStorage.pdf

    Independent rediscovery of ideas happens all the time. As a callow undergraduate I once invented the shift register. My Professor told me to do the reading next time…

  14. jsuros says:

    John,

    One last crazy idea to apply to this whole concept.

    You mentioned Dr. Walthelm’s idea for spraying fuel into the incoming rain of LOXballs to add chemical energy to the applied impulse when the vehicle has speeded up and the kinetic energy differential has dropped. How about the opposite problem? What if you wanted to exchange momentum with a stream of volatiles that was moving hundreds of km/s relative to your vehicle.

    This is way out there, but I can think of several potential sources of volatiles at these energy levels. Maybe we’ll spot an asteroid transiting the solar system from interstellar space, or find ways of speeding masses up to these levels using mass drivers, or use high acceleration very close to the sun.

    Firing a plume of really high speed rocket exhaust into the oncoming impulse gas might lower the speed of the gas that hits your vehicle from an energy level that would destroy you down to usable levels. You would do this until the velocity differential dropped to tens of km/s, then start injecting fuel when you get down to single km/s.

    I got this idea from a past discussion of adding rocket thrust to aerobraking to slow down faster. It turns out that it wouldn’t work, the plume of exhaust partially lubricates your passage through the atmosphere and the deceleration methods do not add up to the sum of the methods. This is a similar principle to the “supercavitation bubbles” that allow russian skval torpedoes to fly through water at 200 knots by firing a rocket plume ahead of themselves and then flying through the hole in the water so opened. A better space example would be to approach a planetary atmosphere at a relative velocity of 100 km/s and try aerobraking. Normally you would die, but if you fly behind a hard enough rocket plume you would get some deceleration from your passage through the atmosphere and survive.

    Like I said, a crazy idea. I wonder if it could ever work in practice?

  15. john hare says:

    Jsuros,

    The very high speed gas impacts can be done as in project Orion. Another that is mentioned at times is Medusa, which is a spaceship with ‘parachute’ which spreads the nuclear blast over a much larger area and is a lighter shock absorber. There would be a lot less ‘fuel’ required at solar escape velocities is all. I think this might be the seed of a method of exploring the outer solar system economically.

    His Hydrogen would be in the rocket chamber just before LLOX impact so that it would operate as a pulsed combustion rocket with external LOX supply. His numbers assumed a perfect rebound instead of the 50% that I did. So that 2,200 m/s LLOX impact would have the same net impulse as a 4,400 m/s LOX/H2 rocket exhaust velocity per pound. At 1 km/sec impact, on board Isp would be ~3,500.

    I never picked up on the higher level directories trick, thanks. I think I could win a pool for least formal education on this site.

  16. Bob Steinke says:

    As far as independent discovery, this method is a lot like the capture tube idea without a tube.

    http://www.islandone.org/LEOBiblio/SPBI1CT.HTM

  17. kert says:

    http://www.esa.int/SPECIALS/Aurora/SEMT8WWIPIF_0.html
    iMARS working group put out their latest Mars sample return mission report this summer. I believe they pegged the price tag of the mission around 6-8 Billion.

    Most of the criticism of it was directed at two-launcher architecture, with claims that autonomous planetary rendezvous has never been done before hence it being too risky.
    Well, Orbital Express ASTRO/NextSat pair, with the expertise of Boeing, Ball Aerospace and MDA combined performed a near flawless coreography of mutiple hydrazine transfers last summer.

    Now with all this in mind, can anyone propose a cheaper or more capable MSR ? I believe they have competitions and prizes for that by the way.
    See the iMARS_Report_July2008.pdf linked above.

  18. Eric Collins says:

    I’ll throw in one more variation on a the current theme.

    When I first read this, I was thinking that it would be nearly impossible to hit a moving target (on a suborbital trajectory) with a stream of snowballs (LOX balls, whatever) hurled from the moon several days earlier. I guess it would be the responsibility of the pilot of the suborbital vehicle to be in the right place at the right time to get in the way of the incoming snowballs.

    Then I started thinking about the Bussard ram scoop. It might be possible to generate a magnetic funnel to collect the snowballs as they are approaching the vehicle. The snowballs themselves would probably have way to much kinetic energy/linear momentum to be captured in such a way. However, if they were to be vaporized (as you suggest) and also ionized, then it may be possible to channel the material into a nozzle/thrust chamber (either in a muzzle loading or perhaps a ram-scoop configuration).

    Chances are good that this idea has also already been considered. It’s new to me, though, so take it for what it’s worth (about $0.02).

  19. john hare says:

    Eric,

    Check out the link Sjv supplied. Dr Walthelm worked this idea over years ago with hundreds of robotic spacecraft shepherding the snowballs to the precise trajectories.

    I got a nice reply from him describing some of his viewpoint.

  20. PeterH says:

    On the tangent of magnetic coupling between the spacecraft being orbited and the reaction mass being thrown at it, do that and the reaction mass doesn’t need to be a vapor. A magnetic scoop on the spacecraft could draw momentum from a stream of iron pellets. Or a train of large magnetized rings could fly over the spacecraft, each giving it a modest boost. The rings could then employ a high ISP or propellant-less re boost.

    Probably as many variants on momentum transfer launch as we can think of means of transferring momentum without destroying the spacecraft or cargo.

  21. john hare says:

    PeterH,

    Tether, iron pellets, or vapor, energy of position is possibly the first lunar marketable resource.

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