We need a better way to get to space

[lmm]

Much as I love to cheer for British engineering, I don't understand the logic here. A rocket would require an expensive inspection before reuse but a spaceplane wouldn't? Why?

Also not one SABRE engine has even been built yet, whereas SpaceX has got very close to landing their rockets.

[dredmorbius]

SpaceX have landed their rockets.

Just not ... in one piece.

[rm_-rf_slash]

I'm no rocket scientist but I could imagine rockets having a place in regular space travel. Lets assume that we can harness solar power efficiently and safely store the extra energy in hydrogen and oxygen gas. Then let's say that we could construct sturdy and modular components that can be disassembled and re-assembled at some kind of orbital station, so that the boosters that take people into orbit for whatever reason could be rebuilt in orbit to carry a load of asteroid-mined metals back to the surface.

Again, I don't know any of the mechanics or physics, but if energy was abundant and parts could be reused, would rockets really be all that bad?

[7952]

Sea Dragon [1] is slightly similar to that.

Fuel is a small part of the cost of a rocket, most of the cost is in the engines and structures. Cheap production of hydrogen or oxygen is unlikely to make things much cheaper.

Also, any mass left over at engine cut-off requires a large quantity of fuel at lift-off and possibly necessitating a larger more expensive rocket. This would make re-purposing of boosters in orbit less likely.

[1] https://en.wikipedia.org/wiki/Sea_Dragon_(rocket)

[drewg123]

I was hoping the article would talk about space elevators, and not space planes. I'm eagerly awaiting materials science and geo-politics to mature enough to allow the construction of space elevators.

https://en.wikipedia.org/wiki/Space_elevator

[gjulianm]

I think the problem with space elevators are not as much with the materials but with the logistics of deploying that. How do you get the cable up there? You can't just shoot up a rocket with a cable attached and expect the cable to stay upright: it would fall down unless you give it horizontal speed. But if you do that, you'd probably end up orbiting the Earth and tying it up with the cable.

The other option would be dropping the cable down, but you'd probably end up with a similar problem. I'm no physicist, but I'm pretty sure that dropping that amount of mass would shift the center of mass of the satellite-cable system and mess with the orbit.

Even if you manage to deploy the cable, you'd still have the problem of the counterweight. I've read that proposed solutions include a captured asteroid (we've just been able to land - or crash, depending on how you see it - in one), a space station/spaceport (that's definitely not cheap), an extended cable (which probably would require even more complex materials) or junk from the construction (still the same problem).

And we still haven't got to the point of security. How do you keep things (space junk, satellites, meteors) from hitting the cable? What would we do if several kilometers of ultra-strong cable fell down into the earth?

I think that space elevators are a nice fantasy, and just that. When we have mature enough materials and geopolitics, we'd probably be better off using them on other methods that seem to be far more viable.

[Balgair]

FYI for all the readers here: Carbon nanotubes won't work, the phonon effects (lattice interactions) in that very large crystal usually add up to break them after a few cm. Think of it like like a very narrow and very long tube half filled with water. There are vibrations along the length of it, some big and some small in amplitude. When those random waves in the water tube interact, they can add up, sometimes so much so that they break the tube. I know that is now totally correct, but that's the gist.

http://www.ruf.rice.edu/~rau/phys600/p273.pdf

Many more here:

https://scholar.google.com/scholar?q=carbon+nanotubes+phonon...

[avmich]

I used to think space elevators are practically impossible because of interactions with lower flying space objects. Now I'm less sure; perhaps we can have a technology of active avoidance.

Other problems - like an extremely capable cable material, ways to climb up and down etc - are getting gradually solved over last years, so I'm cautiously more optimistic than before.

[jcfrei]

I don't really see the benefits of space elevators, to be honest. At an altitude of 100km the gravity is still virtually the same. And you still need a huge amount of fuel in order to put your rocket/plane into orbit. Unless you build an elevator with a height of 42'164km (geostationary orbit) - but that seems unrealistic to me.

[7952]

This thread [1] gives a good explanation of why Skylon should be treated with scepticism.

[1] https://m.reddit.com/r/engineering/comments/2wstn6/i_am_very...

[blisterpeanuts]

It's a slick looking video, but what about reentry? It's not that hard to get a ship up there (the X-15 was flying to the edge of space 50 years ago), and launching like a jet plane obviously has many advantages over rockets, but when it comes back down it's going to hit the atmosphere at a pretty high velocity, unless it's carrying enough fuel to gradually lower itself back into airspace where the jets can kick in. The craft in the video does not appear to have VTOL capability.

But, if they can solve such problems, great. I'm thinking that eventually we'll have some kind of electrical or hybrid mass driver (catapult) system for getting non-human cargo into low orbit[1], much cheaper (and quieter) and obviously could accomplish many launches a day for one-way missions.

You could get a large space station or interplanetary craft up there rather affordably using this approach. Specialized reentry vehicles as well. Launch the parts cheaply, robots assemble the parts in orbit, then launch the humans expensively.

1. https://en.wikipedia.org/wiki/Mass_driver

[Amorymeltzer]

Space planes should absolutely be part of our strategy, but their effectiveness diminishes once you get past LEO. An effective program would have different vehicles for different purposes, using the right tool for each job.

[nickff]

Taking mass to low earth orbit (LEO) is the gating item to increased space travel and exploration; Skylon, SpaceX, Blue Origin, and Orbital Sciences are all focused on reducing this cost. It is quite well understood that outside of plans like Mars Direct and Semi-direct, interplanetary and interstellar travel will require other technologies such as novel electric and nuclear drives, but we are simply not at a point where that is an issue yet.[1][2]

[1] https://en.wikipedia.org/wiki/Ion_thruster

[2] https://en.wikipedia.org/wiki/Nuclear_thermal_rocket

[rikkus]

20 years ago, I remember dreaming up a train pulling a cable with a glider at the far end. I'm sure there are many technical issues with this approach, possibly including the cable needing to be incredibly strong, light and flexible. Please tell me it would work, though, as I still enjoy the mental image.

[nickff]

Reaching orbit is mostly an issue of velocity, not altitude. This is why balloons can get very high, above of almost all earth's atmosphere, while being far from orbit. Rockets spend most of their ascent traveling nearly horizontal to the ground (they only go straight up at the beginning to get out of the densest part of the atmosphere).

[skizm]

So is infertility in astronauts still a problem? I could be totally wrong, but I was under the impression we haven't solved the problem of increased radiation negatively affecting fertility in both male and female astronauts.

[simonh]

I'd have thought sperm/egg freezing would do the trick.

[Mvandenbergh]

For all that effort to reduce oxidiser mass by using atmospheric oxygen, it's still 80% propellant by mass. Saturn V was 85%.

Still impressive if they can make it work, since of course Saturn V wasn't reusable.

[avmich]

So, with Saturn-5 only 15% was dry mass - and with Skylon 20%? That's 33% increase. Moreover, Saturn-5 was staged - and Skylon is single-stage, and have single stage to orbit with 20% dry mass looks somewhat like a miracle.

[anon8764]

www.et3.com gradually leading up to the top of everest, jettisoning the capsule (6,500 km/h (4,000 mph)) to break out of the atmosphere.

I have not done the math, physics, etc on this, but it's an interesting idea worth exploring.

But that said, do we really belong in space when we cannot care for our own? Wouldn't that be akin to giving sugar to ants? only multiplying suffering and cruelty exponentially in space? Perhaps a refactoring of our culture and our methods of using/allocating/expending resources should be our first priority.

[grogenaut]

If people had waited to leave Europe until the 1970s the culture had been "refactored" enough for the masses, I doubt the world would have advanced as far as it had and the pressure of the population growth from industrialization would have caused some real issues. Actually I think it might be refactored even worse for the masses. Letting the average person go out and build new things helped a lot.

Also, do you really think we can only fix one problem at a time? Did the birth of the transistor stop the civil rights movement?

[reitanqild]

(anon8764 was downvoted when I wrote this.)

I disagree but still upvoted this to get it to 0. I find the tought interesting but wrong. It seems more suffering is caused by various misguided attempts at refactoring culture etc and less by technology.

National socialism and communism are two widely known attempts at refactoring culture that has created more misery than all technological advances combined so far.

[noir_lord]

Pushing boundaries technologically has a tendency to pull others along with it, accessing space cheaply would have the potential to create entire new markets and access to new resources all of which would help in the long term everyone else.

[iamcurious]

Interesting, let's say it should be our first priority, how does that translate into action? Please remember that mobilizing large amounts of people towards a goal is hard problem, specially when the goal involves copious amounts of research and experiment.

[aggieben]

Giant railguns. That is all.

[iwwr]

Light-gas guns may be a good contender while railguns are sorted out. https://en.wikipedia.org/wiki/Light-gas_gun

[baldfat]

Squished human beings, but good for some cargo. Would be cool if we could shoot fuel and metal into space, but the heat would be through the roof through the first layer of atmosphere.

[acd]

Tango that, how about a space railgun that is launched either from earth or from a high airplane?