Space travel without combustion or nuclear power. (Thought experiment/discussion.)

[Hyperspace Industries]

I read recently that in my home country it is illegal to own more than a small amount of model rocket fuel. 

This got me thinking: What if we couldn't use combustion rockets, or nuclear propulsion? What insane (or not) measures would we need to go to, to be able to explore space?

First off, a few rules:

1. All technology must either exist completely (cold gas thrusters, ion engines, propellers) or need relatively little new engineering (so skyhooks are allowed, but not space elevators).

2. Combustion is allowed in small parts, so, internal combustion engines and jet engines are allowed, but not rocket engines.

3. Nuclear energy and propulsion is entirely banned. No fission, no fusion, not on the ground, in space or anywhere else.

[lrd.Helmet]

I think your biggest hurdle would be escaping earths atmosphere. Nowadays we use brute force to get up there and non combusting rocket engines don't provide enough power. Maybe a rail gun to accelerate you spaceship and yeet it into orbit?

[Piscator]

Well, I think there was talk about using ground-based lasers (solar-powered in your scenario) to heat a rockets reaction mass to the necessary levels, but I don't know how seriously this can be taken. I guess heating the right parts and keeping the others cool might turn out rather difficult.

[mikegarrison]

Travelling through space is easy. It's starting or stopping or steering that is the difficult problem.

[kerbiloid]

Thanks to Galileo and his relativity principle, just stay where you are, and the whole universe will flow around you.

[magnemoe]

On 12/24/2021 at 3:36 PM, Piscator said:

Well, I think there was talk about using ground-based lasers (solar-powered in your scenario) to heat a rockets reaction mass to the necessary levels, but I don't know how seriously this can be taken. I guess heating the right parts and keeping the others cool might turn out rather difficult.

It was an company thinking of using microwaves for this. To make it simpler do this as 3 stages, first is air drop from a plane second is an air breathing second stage as in heating air and 3rd is the orbital stage with reaction mass. Second stage should be pretty easy to recover, hit it with an microwave to give it trust then needed. 
I added the air drop and two stages who the company did not have as it you don't need to try to take off this with, just hit it with microwaves 12 km up.

----
The reason rocket fuel is restricted is that its very close to gunpowder, its limits on how much gunpowder you can keep to and that is easier to regulate with gun control. 
Lots of competitive marksmen prefer to load their own ammo, but they are known. More danger someone with lots of rocket fuel does something kerbal, or hold my beer. 

Now  as an company with permits you can do other stuff like fire artillery or launch missiles from planes who make sense if you make artillery or shells or missiles. 
Some guy at an forum said their company Learjet was pretty rare in having under wing hard point for missiles and an console for launching them as they was testing some missile. 
They also had pods for tracking the missile and computers but the launch system had lots of reed tape and restrictions. 
 

[tater]

https://www.transastracorp.com/apis-spacecraft

 

[Second Hand Rocket Science]

Maybe solar sails? Surprised no one has mentioned them yet. If we could make a laser that produced a strong enough stream of photons and directed it onto a solar sail, it just might be enough to escape Earth's atmosphere. However, photons would probably dissipate on Earth much quicker than in the cold vacuum of space which would mean for every meter up you flew you would have less power. Once in space it would be easy enough to direct the solar sail towards the Sun, but now we encounter another problem with solar sails.

Solar sails pretty much can't be controlled. You either direct the solar sail towards the Sun and see which direction the thrust makes you go or have no thrust. You really can't control orbital maneuvers like prograde and retrograde, because you most likely will only have prograde at your disposal. Even if the solar sail was able to move on hydraulics, you probably would just have less and less thrust until you had none.

On 12/26/2021 at 8:20 PM, tater said:

https://www.transastracorp.com/apis-spacecraft

 

That Omnivore engine is really interesting. It sounds like fusion power... actually, it sounds exactly like a fusion reactor from the future! Something reacts with an everyday item e.g. any liquids with the sun in the Omnivore, sea water and some sort of fancy chemical mix of Tritium and Helium-3 in a fusion reactor. There is one bad thing about this; also like the fusion reactor, this is the sort of thing that will be "Coming 2023!" this year, then in 2023, "Coming 2024!" and then in 2024 "Coming... uhhhh... soon?" 

Edited January 9, 2022 by Second Hand Rocket Science

[Hyperspace Industries]

59 minutes ago, Second Hand Rocket Science said:

That Omnivore engine is really interesting. It sounds like fusion power... actually, it sounds exactly like a fusion reactor from the future! Something reacts with an everyday item e.g. any liquids with the sun in the Omnivore, sea water and some sort of fancy chemical mix of Tritium and Helium-3 in a fusion reactor. There is one bad thing about this; also like the fusion reactor, this is the sort of thing that will be "Coming 2023!" this year, then in 2023, "Coming 2024!" and then in 2024 "Coming... uhhhh... soon?" 

Nope, it's solar thermal, decent isp (think nerva without nuclear reactor bureaucracy) decent thrust.

Mirrors point sunlight to heat the liquid, water would make more thrust with lower isp, hydrogen more isp,  lower thrust.

Sorry if I misunderstood your comment.

[Second Hand Rocket Science]

Just now, Hyperspace Industries said:

Nope, it's solar thermal, decent isp (think nerva without nuclear reactor bureaucracy) decent thrust.

Mirrors point sunlight to heat the liquid, water would make more thrust with lower isp, hydrogen more isp,  lower thrust.

Sorry if I misunderstood your comment.

Nope, you've not misunderstood my comment. In fact, I've just misunderstood how the Omnivore works. Thanks for pointing this out!

[wumpus]

There was Escape Dynamics and their attempt to build a SSTO craft by heating it with microwave power as it lifted off to orbit.  Isp should approach NTR, but have even more issues of the "heating chamber" heating up everything around it (including the less focused microwaves).  https://en.wikipedia.org/wiki/Escape_Dynamics

It was my favorite "power point rocket company".  Probably 20 years before their time*, but I suspect that once Starship lands (with or without a crew), that cutting fuel costs will be a real thing in space research.

Also there are electrodynamic tethers for raising your orbit using electricity once you are in orbit (of the Earth, don't try it on the Moon, Mars, or any other body without a magnetic field).

* this is not a good thing.  You can't make payroll until the infrastructure exists to get things going.  Building a "steam engine before steam engine time" kills many people every time the pressure vessel explodes.  Generally speaking, the whole "great inventor" theory of  technology completely misses that most of the inventions are useless before the infrastructure is ready, and had the "great inventor" merely slept in that day the next day someone else would have done it.

[Rakaydos]

Balloon launch is a wonderful thing- you can get to the edge of space  just by displacing the very air that's difficult to climb through. However, you dont gain the velocity advantage that  a staged rocket would have, getting to the same altitude. You're effectively launching from a small pad 40-50 miles up.

Spinlaunch is working on a purely kinetic circular accelerator. It still has some problems to sort out, but using a similar system in the soft-vacuum around a high altitude baloon could plausably get you to orbital velovity, albet with a PE only 50 miles up.

From there, something like VASMIR, a high thrust electric propulsion engine, might be able to circularize before  the orbit decays.

[magnemoe]

On 1/10/2022 at 8:13 PM, wumpus said:

There was Escape Dynamics and their attempt to build a SSTO craft by heating it with microwave power as it lifted off to orbit.  Isp should approach NTR, but have even more issues of the "heating chamber" heating up everything around it (including the less focused microwaves).  https://en.wikipedia.org/wiki/Escape_Dynamics

It was my favorite "power point rocket company".  Probably 20 years before their time*, but I suspect that once Starship lands (with or without a crew), that cutting fuel costs will be a real thing in space research.

Also there are electrodynamic tethers for raising your orbit using electricity once you are in orbit (of the Earth, don't try it on the Moon, Mars, or any other body without a magnetic field).

* this is not a good thing.  You can't make payroll until the infrastructure exists to get things going.  Building a "steam engine before steam engine time" kills many people every time the pressure vessel explodes.  Generally speaking, the whole "great inventor" theory of  technology completely misses that most of the inventions are useless before the infrastructure is ready, and had the "great inventor" merely slept in that day the next day someone else would have done it.

Steam engine time  that is from discworld is it not? 
And yes to steam engines the problem was precision and metallurgy.  Its not random chance that guns kept getting better at the same time. 
For other technology marked is often the limiting factor. TV is an niche marked, yes its useful for guiding missiles and you can use it to watch stuff from far away so it can be used for surveillance at dangerous places like prisons. 
And yes lots of infrastructure heavy projects has the same issues. 

[KerikBalm]

Just pointing it out: technically speaking, monopropellant, TNT, nitroglycerin, etc do no combust, they just very energetically decompose.

[wumpus]

On 1/13/2022 at 12:51 PM, magnemoe said:

Steam engine time  that is from discworld is it not? 
And yes to steam engines the problem was precision and metallurgy.  Its not random chance that guns kept getting better at the same time. 
For other technology marked is often the limiting factor. TV is an niche marked, yes its useful for guiding missiles and you can use it to watch stuff from far away so it can be used for surveillance at dangerous places like prisons. 
And yes lots of infrastructure heavy projects has the same issues. 

Some googling implies that the concept is taken over by "technological determinism", which completely gets it wrong [I'll have to stop using the phrase, sad].  The original was from Charles Fort, so it makes sense that he doesn't understand why steam came when it did.  Also same reason airplanes occurred when they did: as internal combustion engines got more powerful and lighter, it became easier and easier to build an airplane.  The Wright brothers were well aware of this and knew they were pressed for time before better engine builders would "invent" the airplane (there's a motorcycle built by Glen Curtis in the Smithsonian.  Presumably built to test an engine, or as a marketing stunt (I think it set a speed record)).

Probably the bit were "the exception proves the rule" is the Turbo Code.  From 1970-2000ish, there was almost no improvement in digital encoding of transmitted messages (for error correction).  Then, suddenly, someone developed the Turbo Codes which can reach near enough to theoretical perfection with a slight delay as massive calculations are done.  So this invention is decades "late".  Except it isn't the only "perfect" code we currently use.  The other is the LDPC family, which was invented decades "too early" and forgotten until somebody looked hard for patent-free competitors for the Turbo Codes...

[this will teach me to to include a random side rant in a post.  But the topic was so fanciful I thought it was safe.]

[magnemoe]

1 minute ago, wumpus said:

Some googling implies that the concept is taken over by "technological determinism", which completely gets it wrong [I'll have to stop using the phrase, sad].  The original was from Charles Fort, so it makes sense that he doesn't understand why steam came when it did.  Also same reason airplanes occurred when they did: as internal combustion engines got more powerful and lighter, it became easier and easier to build an airplane.  The Wright brothers were well aware of this and knew they were pressed for time before better engine builders would "invent" the airplane (there's a motorcycle built by Glen Curtis in the Smithsonian.  Presumably built to test an engine, or as a marketing stunt (I think it set a speed record)).

Probably the bit were "the exception proves the rule" is the Turbo Code.  From 1970-2000ish, there was almost no improvement in digital encoding of transmitted messages (for error correction).  Then, suddenly, someone developed the Turbo Codes which can reach near enough to theoretical perfection with a slight delay as massive calculations are done.  So this invention is decades "late".  Except it isn't the only "perfect" code we currently use.  The other is the LDPC family, which was invented decades "too early" and forgotten until somebody looked hard for patent-free competitors for the Turbo Codes...

[this will teach me to to include a random side rant in a post.  But the topic was so fanciful I thought it was safe.]

Yes, planes is an good point, people had started to understand how to fly an plane it just lacked an engine but had it not been for the glide flight pioneers it would taken longer. 
And its obviously exceptions to the rule.  A lot of is how an new invention requires another technology to exist for it to be practical. 

[JoeSchmuckatelli]

Okay - stupid knuckledragger question time... 

If earth based lasers can shove a sail sat out of the solar system https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.space.com/amp/laser-sail-centering-breakthrough-starshot.html&ved=2ahUKEwiG3KDagrL1AhVUJEQIHcA_BmEQtwJ6BAgHEAE&usg=AOvVaw3wv9Y56_JRSHUz7KcKtZqA

 

Can a nuclear powered space ship shove itself out with onboard lasers? 

Edited January 14, 2022 by JoeSchmuckatelli

[Rakaydos]

21 minutes ago, JoeSchmuckatelli said:

Okay - stupid knuckledragger question time... 

If earth based lasers can shove a sail sat out of the solar system https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.space.com/amp/laser-sail-centering-breakthrough-starshot.html&ved=2ahUKEwiG3KDagrL1AhVUJEQIHcA_BmEQtwJ6BAgHEAE&usg=AOvVaw3wv9Y56_JRSHUz7KcKtZqA

 

Can a nuclear powered space ship shove itself out with onboard lasers? 

Photon drives have an ISP equal to the actual speed of light. Nothing in this universe can be more efficient. But their practical thrust sucks.

[magnemoe]

5 minutes ago, Rakaydos said:

Photon drives have an ISP equal to the actual speed of light. Nothing in this universe can be more efficient. But their practical thrust sucks.

A bit related the initial breakthrough starshot mission  planned to bounche the laser between the probe and the base station increasing the efficiency many times. 
looks like they has dropped this, however I imagine this would be much better used on an larger probe with an much larger mirror with probe level acceleration say 3% of an g for an cube sat payload rather than 50.000 g for an wafer. 

[wumpus]

22 hours ago, Rakaydos said:

Photon drives have an ISP equal to the actual speed of light. Nothing in this universe can be more efficient. But their practical thrust sucks.

Pretty sure the wavelength of the photon matters (blue LEDs are probably the best you can do now).  And make sure you carefully paint the "exhaust" side of your heat sinks black and the "front" side white.  You'll get a significant amount of thrust from just the heat sinks.

[kerbiloid]

11 hours ago, wumpus said:

Pretty sure the wavelength of the photon matters (blue LEDs are probably the best you can do now)

To provide as effective thrust as hydrogen, the photon should probably be of the nucleon Comton wavelength, ~10^-15 m.

Probably, only a mini-blackhole can accelerate the photons provide photons of such wavelength.

And as the blackhole should be enough light to carry it onboard (say, a charged blackhole in a static electric field), its lifespan would be extremely short.

So, it actually the blackhole should be generated on every ignition.

Thus, the most handy kind of the blackhole is probably a kugelblitz.

And as the kugelblitz is electrically neutral, it can't be held at all. It should appear and immediately evaporate, turning into ultra-high-energy photons.

And as we can only make the kugelblitz be rotating and manage the energy distribution only equatorially, the practically usable kugelblitz explosion can be only spherical.

As the kugelblitz explosion is spherical, it will hit any chamber walls radially and damage them.

Thus, the kugelblitz should be generated and exploded behind the ship and push it forwards.

Kugelblitz Orion.

In turn, the kugelblitz in this case can be made rotating, but not around the ship axis, but perpendicularly.
So, the ship is in its equatorial plane, and more energetical photons generated by the kugelblitz explosion are in this plane, too.
This helps to redistribute the energy and momentum to reduce the sideways loss.

As the kugelblitz is rotating perpendicularly to the ship axis, the photon pushes will be rotating the ship., 
To avoid this, a pair of counter-rotating kugelblitzen should be used.

Probably the kugelblitzen should be not just counter-rotating, but maybe also synchronized to send the photons in counterphase.

To smoothen the energy distribution, the pair of kugelblitzen should be replaced with any even number of them, uniformly distributed around the axis.

The pusher plate should be replaced with a cloud of charged dust in magnetic field.

Thus we come to the ultimate solution - the Mutiblitz Orion.

Actually, just the Kugelblitz Orion, but with multiple ephemerical kugelblitzen.

Edited January 16, 2022 by kerbiloid

[mikegarrison]

On 1/14/2022 at 11:18 AM, wumpus said:

Also same reason airplanes occurred when they did: as internal combustion engines got more powerful and lighter, it became easier and easier to build an airplane.  The Wright brothers were well aware of this and knew they were pressed for time before better engine builders would "invent" the airplane (there's a motorcycle built by Glen Curtis in the Smithsonian.  Presumably built to test an engine, or as a marketing stunt (I think it set a speed record)).

This dramatically downplays what the Wrights actually did.

1) They built the most technically advanced gliders in the world.

2) In the process of learning to fly them, they invented 3-axis control, which all airplanes to this day use.

3) They built their own wind tunnel to test their ideas. In the process they discovered that all the published literature on lift and drag coefficients was wrong. (Well, sort of. It had been experimentally measured both smaller and larger than the true value. The scientific understanding of it was not totally off-base, but it had so much uncertainty that it was a real problem.) They came up with a much better estimate of dynamic pressure. (They knew lift and drag varied as a function of speed squared, but they didn't know the coefficient they experimentally determined was actually 1/2 the air density.) That was extremely important to sizing the airplane.

4) They commissioned their own engine, made (at great expense) out of aluminum.

5) They realized that propeller blades were actually wings, and so they designed them with proper airfoil shapes (that they also tested in their wind tunnel).

Almost all of this was absolutely unique to the Wrights at the time they first flew. Very few people even had come close to understanding any of these things, while the Wright put them all together in a very scientific way, with meticulous lab and flight testing.

Edited January 19, 2022 by mikegarrison

[wumpus]

3 hours ago, mikegarrison said:

This dramatically downplays what the Wrights actually did.

1) They built the most technically advanced gliders in the world.

2) In the process of learning to fly them, they invented 3-axis control, which all airplanes to this day use.

3) They built their own wind tunnel to test their ideas. In the process they discovered that all the published literature on lift and drag coefficients was wrong. (Well, sort of. It had been experimentally measured both smaller and larger than the true value. The scientific understanding of it was not totally off-base, but it had so much uncertainty that it was a real problem.) They came up with a much better estimate of dynamic pressure. (They knew lift and drag varied as a function of speed squared, but they didn't know the coefficient they experimentally determined was actually 1/2 the air density.) That was extremely important to sizing the airplane.

4) They commissioned their own engine, made (at great expense) out of aluminum.

5) They realized that propeller blades were actually wings, and so they designed them with proper airfoil shapes (that they also tested in their wind tunnel).

Almost all of this was absolutely unique to the Wrights at the time they first flew. Very few people even had come close to understanding any of these things, while the Wright put them all together in a very scientific way, with meticulous lab and flight testing.

All true.  But the point  is that even with all that, they knew quite well that a sufficiently skilled engine maker could make a brick fly (although probably not control it without putting in similar time as the Wrights).  They had the advantage of understanding flight, but they needed to pay that for that advanced engine if they wanted to be first.  They also needed a rather strong headwind, something not available for the [planned] 100th anniversary flight of a strong [exact?] replica.

Also they hadn't discovered how badly wind tunnels scale, especially at the size they were using.  But even badly scaled wind tunnels gave more accurate information than the guesses at how aerodynamics worked at the time.

[kerbiloid]

They were aware of the primitivie motorless gliders and the early dirigibles (mid-XIX), so they had to combine.

[Beamer]

Since this is posted in the Science & Space section rather than a rocket building section I'm going to say it...

It's worth noting that most scientific exploration of space has been done from the Earth's surface. By a huge margin. There is very little science that was done in space that hasn't been replicated or even improved on Earth's surface, except of course for the narrow field of science that actually involves putting humans in space, which you don't need for exploration from the surface. Point in case, the upcoming ELT is expected to offer 16 times better imaging than Hubble, and that will be done in a few years (and yes, that does stand for "Extremely Large Telescope" ).

Sure, the various rovers, landers and planetary orbiters have taught us some things we might not have been able to conclusively measure from Earth, but those tend to be very local and directly related to the geographic features of the relevant body and generally fit more in the fields of geography and climate rather than astronomy and cosmology.

In the grander scheme of things, sending up rockets in the pursuit of science and exploration of space is like taking a stroll through your back garden and studying the spider webs you find there. It's interesting and not entirely useless and it prepares you for a possible future trip to the neighbour's lot, but it doesn't tell you all that much about what's "out there".