Rockets are dual-use with ICBMs? No problem; just build a gigantic cannon instead:
The tricky part is convincing Mossad that the gun is purely for civilian use so that they don’t murder you…
Great cite. Thank you.
The OTRAG design planning to have 456 small engines power the first stage reminded me of this: Model Rockets (xkcd.com). And specifically figure 4 therein. Which almost certainly would not go to space on any day, much less to-day. 
ARCA Space is trying to be the next OTRAG:
It’s a steam-powered stage with a rather unimpressive specific impulse.
If that gets funded, it’s a sign that the financial bubble has not yet popped.
Every nickel of investment in new space launch should be on hold until we see the results of Starship’s orbital test. If that test works and the vehicle delivers close to expected performance, then a new bar for cheap space has been set and a model for how to get there proven out.
If Starship works, I don’t think there is even a use case for a space elevator, as a Starship-based space transportation system will already be cheaper. Maybe one day space elevators will ve developed for massive orbital mass transfer to GTO, but they won’t be needed for cheap access to space.
So why invest in something this complex and ultimately expensive? It looks like an amateur 3D modeler’s idea of what a rocket might look like after first hearing about the rocket equation and learning how to cut and padte objects.
Wow. I read ARCASpace’s wiki entry from OTRAG’s. But totally missed that insane impressive device. I’d wondered why wiki had them as a “See also” from OTRAG. Now I know.
To bring us back to the topic of this thread, in another example of an idea before its time, there’s this thing that oddly foreshadows some of Starship itself:
The wacky keeps on coming. Robert Truax was to rocketry sort of what Burt Rutan was/is to airplanes. Unlike Rutan, he’s just a little too far out ahead of the curve to have most of his stuff actually work.
Nah, that rocket would work perfectly in Kerbal Space Program!
No one serious is “investing” in ARCA. They get a few dribbles of money here and there, including seemingly $500k from New Mexico, as well as some crowdfunding and cryptocurrency, but this many steps behind even the weirdest US launch companies. I just posted it because it’s funny. I don’t think it speaks much of the rest of the small launch industry and their (real, but different) problems.
I’m not sure a space elevator ever makes sense on Earth. The problem is capital cost. Even if you can build it, a space elevator will cost several tens of billions and be able to lift a finite amount of mass per year. If that can’t pay for >~5% of the cost of building it, it’s not viable. Starship does not have those same capital costs. Even if the marginal cost is higher, it doesn’t have the problem of having so much money tied up in the system.
I wouldn’t put it quite like that–it’s more that he was too ahead of the curve to get significant buy-in from the people with the money. The Sea Dragon passed an external design review (by TRW), and a number of the basic technologies (like the submerged ocean launch) had already been tested. It almost certainly would have worked.
Whether it would have achieved its claimed $/kg figures, or whether the reusability parts would have panned out, is a different story. But there’s nothing wrong with either the basic physics or the general engineering feasibility.
The first satellite launchers were expensive because they were derived from military missiles that by design were one-use and obsessed with squeezing the last gram of payload out of a launcher of fixed size and weight. We’ve long known that you could make spaceflight a lot cheaper if you used economy of scale. Not only do the fixed costs of conducting a launch get spread over more payload, but the engineering challenges get easier: make a rocket big enough and you can use sheet steel for the tankage instead of foil-thin metal that actually costs more per square meter. The problem is that no one was willing to commit to developing a capacity for million-pound payloads. It’s similar to what critics back in the 1930s said of proposed western hydroelectric projects: “who’s going to buy the power- jackrabbits?”
No sober risk analysis twenty years ago would have supported developing Starship. But Musk said “by golly I’m going to do it anyway”, and did so.
Before that, there was Hitler’s V3. And even earlier, the ‘Paris gun’ from WW1.
I’d like to see some quantitative estimates about this. What is starship’s expected cost to geosync per KG of payload?
If we had a space elevator, it’s just the energy required to lift the payload (minus a few engineering inefficiencies), I might even do a back-of-the envelope myself from basic physics…
Granted, we don’t have a space elevator, or even the unobtanium needed to build one. And it would be an enormous capital expense, and it’s not useful for LEO… but we’re really interested in deeper space here, surely?
Surely it’s easier to ride the elevator to GEO and then boost down to LEO than it is to get into orbit in the first place?
ETA: 7.8km/s to orbit; add 1.8 km/s to account for drag and gravity losses.
Versus 6 km/s to go from GEO to LEO.
That’s actually much closer than I was expecting! GEO is expensive in terms of DV.
Getting to a lower orbit from a higher orbit costs the same as getting to the higher orbit from the lower.
However, if you had a space elevator you could have release points below geosynchronous height that would put you in an eccentric orbit with your target height at periapsis, leaving you with just a circularization burn. Unfortunate in this context that’s the more expensive burn, but it’s still less energy than a straight Hohmann transfer from GEO to LEO.
Disclaimer: everything I know about orbital mechanics I learned from Kerbal. Actually, to be super-Kerbal in this context you’d release with your periapsis far enough into the atmosphere to aerobrake your apoapsis down to your desired height after a few passes, then jettison your heat shield and you’d only need to lift your periapsis from skimming the atmosphere up to target height. That should require less delta-V than circularizing by doing the second half of a Hohmann transfer.
However, if you had a space elevator you could have release points below geosynchronous height that would put you in an eccentric orbit with your target height at periapsis<
If you drop something off a space elevator at a height of, say, 300Km, it is just going to fall to Earth like a stone. Many people don’t realise that the majority of energy used to put a satellite into LEO is not in lifting it a few hundred Km, it’s giving it the speed (kinetic energy) to maintain orbit.
Which is why the various ‘space tourism’ programs that pop above the stratosphere for a few minutes are just gimmicks: nothing to do with any real space program.
A geosynchronous elevator doesn’t have to be skyscraper massive. The first one could be a ribbon with a capacity of a couple of tons. If it broke what didn’t fly away into space or burn up in the atmosphere would float to the ground like confetti. We can’t build one now but short of that there are multiple ways to use tethers for kinetic energy transfer. And before you could build a elevator for Earth you could do so for the moon or Mars with less demanding requirements.
Mars, perhaps; that would be easier. The moon doesn’t rotate fast enough, I think.
Meanwhile: come on Musky-boy, press that button? I really would like to see a viable heavy lift launch system in my lifetime…
The proposed idea is that lunar tethers could have their center of mass at the Earth-Moon L1 and L2 points; because one end would be anchored to the moon stability wouldn’t be a problem.
Yes, I think there are quite a few tether ideas that don’t require such strong unobtanium and might even be possible with current materials. We’ve got to get them up there somehow first, though, and there’s the issue of economic payback viability…
At 300km, it’ll drop pretty much like a stone, because its radial velocity is not much faster than it is at the surface. As you move up the elevator, however, your radial velocity increases (still 360 degrees/day, but each degree covers a greater distance since the radius is larger as you go up, so you’re traveling at higher metres/second) and the required velocity to maintain an orbit at that elevation decreases. At geosynchronous orbit height, these two velocities coincide. Just below GEO height, you’ll have most but not quite all of the velocity you’d need to orbit at that height. If you released from the elevator there, you’d end up in an eccentric orbit with your release point at apoapsis, and your periapsis somewhat lower (more eccentricity the lower you release). You can give yourself a periapsis of any height you want by releasing at the appropriate height. But the lower your target periapsis, the greater your eccentricity will be.
That’s not the way to look at it. You have to look at all the system costs. How much mass is the elevator? How much will it cost to manufacture, and how long will that take? Capital costs have to be recouped.
Once you have your elevator, how long will it last before it has to be dismantled? How much mass can be put in orbit per day, and what are the operating costs? How much mass can be lifted over its lifespan? How do you do maintenance and inspections on 24,000 miles of cable? What does insurance look like? How much damage will be done if the elevator is hit by orbital debris, and how do you mitigate that risk?
Then there’s the problem that not only does the elevator only really work for objects destined for GEO and beyond, but it also only puts satellites in an equatorial orbit. So factor in the cost of boosting satellites, changing orbital inclination when necessary, etc.
Compare that to a reusable tin can that can place anything under 150 tons in whatever orbit you want, for the cost of fuel and a much smaller set of fixed costs.
There are a million reasons why the real cost of a space elevator will not even be close to just the energy cost of putting a kg in GEO.