Jump to content

Which of these (listed below) is the best method for sublight space travel?


Maximum7

Recommended Posts

Lets just assume that everything I list below is possible (because some will be based on unknown energies). I have provided some links.

Take into account when choosing the drive

1.)How efficient and easy to maintain is it?

2.) How fast it can go?

3.) Anything else that can go wrong.


Here are the options

1.) Antimatter rocket

2,) Ion drive

3) Bussard ramjet

4.) Dipole drive https://www.nextbigfuture.com/2018/...ss-space-propulsion-concept-dipole-drive.html

5.) Fusion rocket

6.) Halo drive  https://arxiv.org/abs/1903.03423

7.) Solar sail

8.) EMdrive https://en.wikipedia.org/wiki/RF_resonant_cavity_thruster

9.) Photon rocket

10.) Magnetic sail

11.) Vacuum energy sail

12.) Nano electrokinetic thruster https://en.wikipedia.org/wiki/Nano_electrokinetic_thruster

13.) Quantum vacuum thruster https://en.wikipedia.org/wiki/Quantum_vacuum_thruster

14.) Plasma drive

15.) Beam powered propulsion https://en.wikipedia.org/wiki/Beam-powered_propulsion

16.) Nuclear photonic rocket https://en.wikipedia.org/wiki/Nuclear_photonic_rocket

17.) Pulse detonation engine https://en.wikipedia.org/wiki/Pulse_detonation_engine

18.) Mach Effect Drive https://en.wikipedia.org/wiki/Mach_effect

19.) Unruh radiation propulsion drive https://www.google.com/amp/s/www.vice.com/amp/en_us/article/7x3ed9/darpa-is-researching-quantized-inertia-a-theory-of-physics-many-think-is-pseudoscience

Edited by Maximum7
Link to comment
Share on other sites

2 hours ago, Maximum7 said:

Lets just assume that everything I list below is possible (because some will be based on unknown energies). I have provided some links.

Take into account when choosing the drive

1.)How efficient and easy to maintain is it?

2.) How fast it can go?

3.) Anything else that can go wrong.


Here are the options

1.) Antimatter rocket

2,) Ion drive

3) Bussard ramjet

4.) Dipole drive https://www.nextbigfuture.com/2018/...ss-space-propulsion-concept-dipole-drive.html

5.) Fusion rocket

6.) Halo drive  https://arxiv.org/abs/1903.03423

7.) Solar sail

8.) EMdrive https://en.wikipedia.org/wiki/RF_resonant_cavity_thruster

9.) Photon rocket

10.) Magnetic sail

11.) Vacuum energy sail

12.) Nano electrokinetic thruster https://en.wikipedia.org/wiki/Nano_electrokinetic_thruster

13.) Quantum vacuum thruster https://en.wikipedia.org/wiki/Quantum_vacuum_thruster

14.) Plasma drive

15.) Beam powered propulsion https://en.wikipedia.org/wiki/Beam-powered_propulsion

16.) Nuclear photonic rocket https://en.wikipedia.org/wiki/Nuclear_photonic_rocket

17.) Pulse detonation engine https://en.wikipedia.org/wiki/Pulse_detonation_engine

18.) Mach Effect Drive https://en.wikipedia.org/wiki/Mach_effect

19.) Unruh radiation propulsion drive https://www.google.com/amp/s/www.vice.com/amp/en_us/article/7x3ed9/darpa-is-researching-quantized-inertia-a-theory-of-physics-many-think-is-pseudoscience

 

Best? That really depends on what you want to do, how safe you want to be, and how long you you want the trip to take.

Some of the drives listed are theoretical and have not been proven to be possible to make. Others like antimatter and fusion only get their best performance at temperatures that would melt your engine. So can they break even almost with nuclear for performance in space, since rocket engines cannot survive the heat that would allow one to run antimatter and fusion engines at much hotter tempertures for longer burn rates and higher thrust.

 

Photon would wreck everything behind it for miles. Pusher plate is possible but is kind of like a lowered powered photon drive that still wrecks stuff for miles behind the ship.

For practicality, speed, and safety optimization, meaning we CAN do it, it would be nuclear or ion with a nuclear reactor.

Both are slow, but nuclear is faster.

 

That said, none is good enough for scifi unless you are willing to accept and deal with each drive's drawbacks.

Edited by Spacescifi
Link to comment
Share on other sites

Beam propulsion is really the only practical method for relativistic velocities with our current understanding of physics.

That said it has its own problems, but these could potentially be overcome. Though of course no matter what you do you have some very powerful hardware on your hands...

The problem with beam propulsion is that it needs to either limit the cruise velocity to allow deceleration with some other propulsion system or it needs infrastructure in the target system to be present. Of course a self replicating system (if that ever becomes possible...) could potentially seed nearby stars with the necessary infrastructure in a fairly decent amount of time, allowing human scale missions to nearby star systems in just a few centuries (maybe less) after the first few seed vehicles are deployed, and with fairly short (proper) travel times for human crews. (side note, I've often pondered what slower than light interstellar civilization would look like, how it would work, the technology in use, and so on)

Photon beams aren't as efficient as mass beams in most cases so they seem like a really good option. Could even be used for rapid interplanetary travel and missions to the Kuiper belt and beyond.

Link to comment
Share on other sites

2 hours ago, Bill Phil said:

The problem with beam propulsion is that it needs to either limit the cruise velocity to allow deceleration with some other propulsion system or it needs infrastructure in the target system to be present.

Or it needs an expendable part of the ship to separate and become a retrograde reflector.

Link to comment
Share on other sites

Ion/Plasma drives, and solar/magnetic sails are too weak to be considered sublight engines. They would help speed up interplanetary travel by potentially a good amount, but you won't be getting to another star anytime soon.

The Halo drive is only good if you have a black hole nearby already (which we don't), so for our intents, is useless.

Em drive, and other similar engines are dubious at best.

Beamed sails, and Orion are good for more near-term interstellar travel if we really want it, but it would still take up to a century or more to reach another star. And in the beamed sails case, unless you have another drive, or some other way to slow the sail down on the other end, it better be a one-way probe.

I would say fusion is one of the best methods (and one we could have within a century or so), after antimatter. Beamed sails are good as well once you can get an interstellar network set up.

Edited by Spaceception
Link to comment
Share on other sites

14 hours ago, Bill Phil said:

The problem with beam propulsion is that it needs to either limit the cruise velocity to allow deceleration with some other propulsion system or it needs infrastructure in the target system to be present. Of course a self replicating system (if that ever becomes possible...) could potentially seed nearby stars with the necessary infrastructure in a fairly decent amount of time, allowing human scale missions to nearby star systems in just a few centuries (maybe less) after the first few seed vehicles are deployed, and with fairly short (proper) travel times for human crews. (side note, I've often pondered what slower than light interstellar civilization would look like, how it would work, the technology in use, and so on)

In the classic Niven and Pournelle book The Mote in God's Eye, the jumpdrive-capable human empire encounters its first intelligent aliens in the form of a sublight beamed-power ship.  This ship solved the deceleration problem by being a huge solar sail.  It was sent on its way with a massive battery of lasers then planned to stop by using its sail to brake during a close pass by the destination star.  The main problem the aliens had with this scheme was political.  They didn't have a single world government and their civilization was never stable due to internal pressures.  So they'd nuked themselves back to the Stone Age MANY times in their very long history.  One such episode happened while this ship was en route, with its launching lasers being used in their nth world war.

That's the main problem I see for humans and beamed power, too.  All spacedrives worthy of the name are also WMDs, due to being able to direct the vast amount of energy required in the desired direction.  I see beamed power as more vulnerable to misuse than most other schemes where the power is aboard the ship.  For example, an Orion ship is a high-capacity nuclear bomber in orbit but it can be built and fueled far enough away to pose little real threat.  Even if it does some start dropping nukes on Earth, there's time to intercept them.  With beamed power, OTOH, all you need is a few mirrors in orbit and brief flicking of the beam to them, and you can vaporize anything you want without significantly slowing the ship.

Link to comment
Share on other sites

12 hours ago, pincushionman said:

The advantages of both are that we know they work; we already understand how they could be built; and we already understand their limitations well.

Not only that , the only thing preventing us from utilizing them is our own misguided obeisance to the opinions of people [-snip-].

Edited by Starhawk
Redacted by moderator
Link to comment
Share on other sites

On 9/14/2019 at 9:47 PM, pincushionman said:

I'm a little sad these aren't already on the list. The advantages of both are that we know they work; we already understand how they could be built; and we already understand their limitations well.

I can't say that "we know" the NSWR works.  There's quite a bit of disagreement on that score.  I'm inclined to be dubious, myself.  I don't trust Zubrin--he's got too much of the airs of a wild-eyed zealot for my taste.  But let's say everybody agrees on the numbers and the numbers indicate it would actually work.  That's just the beginning of the problem.  Designing the tanks so the fuel doesn't just go critical for no reason seems even less likely than agreement on the underlying numbers.  And even if that is possible, it will be hugely expensive just to develop the necessary manufacturing plant, must less build the actual system.  And even if you get past that, you still have the very real issue that a fuel leak will likely cause the ship to explode.

http://www.projectrho.com/public_html/rocket/enginelist2.php#nswr

 

Link to comment
Share on other sites

On 9/16/2019 at 9:41 AM, Geschosskopf said:

I can't say that "we know" the NSWR works.  There's quite a bit of disagreement on that score.  I'm inclined to be dubious, myself.  I don't trust Zubrin--he's got too much of the airs of a wild-eyed zealot for my taste.  But let's say everybody agrees on the numbers and the numbers indicate it would actually work.  That's just the beginning of the problem.  Designing the tanks so the fuel doesn't just go critical for no reason seems even less likely than agreement on the underlying numbers.  And even if that is possible, it will be hugely expensive just to develop the necessary manufacturing plant, must less build the actual system.  And even if you get past that, you still have the very real issue that a fuel leak will likely cause the ship to explode.

Like Orion, it's less a question of science, we know the science quite well, partly a question of engineering, and certainly a question of politics.

This kind of stuff was basically figured out by the 1960s, it's just a question of which groups among us have the moral fortitude to treat those people and groups, that would sabotage such a revolutionary leap in spaceflight, as the pickpockets and racketeers that they are.

 

 

Link to comment
Share on other sites

On 9/16/2019 at 9:41 AM, Geschosskopf said:

I can't say that "we know" the NSWR works.  There's quite a bit of disagreement on that score.  I'm inclined to be dubious, myself.  I don't trust Zubrin--he's got too much of the airs of a wild-eyed zealot for my taste.  But let's say everybody agrees on the numbers and the numbers indicate it would actually work.  That's just the beginning of the problem.  Designing the tanks so the fuel doesn't just go critical for no reason seems even less likely than agreement on the underlying numbers.

Oh, it would work. Whether it would work at peak efficiency is another question, but it would definitely work.

I wonder if you could build an open-cycle molten-salt reactor that could expend a working fluid like a NSWR during launch and then function more like a fission fragment rocket for high specific impulse during interplanetary flights. A vehicle based on this engine would need to use drop tanks for launch but would otherwise be pretty fully reusable and could fly single-stage to the surface of Mars easily enough.

Link to comment
Share on other sites

10 hours ago, Nothalogh said:

Like Orion, it's less a question of science, we know the science quite well, partly a question of engineering, and certainly a question of politics.

 

2 hours ago, sevenperforce said:

Oh, it would work. Whether it would work at peak efficiency is another question, but it would definitely work.

 

Well;, you believe crazy Zubrin, I'll wait to see whether the justifiably skeptical, arguably saner people have to say.  And as mentioned, even if the numbers ultimately say it could work in theory, and even if the politics get sorted out, there's still the immense practical engineering problem of simply building the fuel tanks at all, let alone making them even remotely safe from punctures in operation.  These issues put the NSWR in the same category as drives that require the presence of a black hole or the like.  Maybe possible in theory but utterly impractical to build.

Link to comment
Share on other sites

1 hour ago, Geschosskopf said:

Well;, you believe crazy Zubrin, I'll wait to see whether the justifiably skeptical, arguably saner people have to say.  And as mentioned, even if the numbers ultimately say it could work in theory, and even if the politics get sorted out, there's still the immense practical engineering problem of simply building the fuel tanks at all, let alone making them even remotely safe from punctures in operation.  These issues put the NSWR in the same category as drives that require the presence of a black hole or the like.  Maybe possible in theory but utterly impractical to build.

The challenges are not substantially different than those involved in building molten-salt reactors or pressurized heavy water reactors. There are some critical elements that need work, but the engineering problems are really not that bad.

Link to comment
Share on other sites

1 hour ago, sevenperforce said:

The challenges are not substantially different than those involved in building molten-salt reactors or pressurized heavy water reactors. There are some critical elements that need work, but the engineering problems are really not that bad.

Um, no..    Not.  At.  All.  The NSWR has NOTHING in common with a normal (or even molten salt) reactor, other than they both involve uranium.  Thus, the challenges are ENTIRELY different.

In the conventional reactors you mention, the uranium is solid, in the fuel rods, and doesn't move.  The pressurized water or molten salt is merely coolant, absorbing heat from the solid core and carrying it away to keep it from melting.  As this fluid circulates through the fuel rods, it picks up bits of radioactive solids so is usually not the actual working fluid---otherwise you'd contaminate the turbines, which would complicate maintenance.  So instead, the coolant goes through a heat-exchanger to pass the heat on to the actual working fluid, which is water in a separate set of pipes.  This water turns to steam, spins the turbines to make electricity, condenses, gets cooled in the big towers, and back into the heat exchanger.

A NERVA is essentially a conventional reactor just like the above.  You still have a solid fuel core around which you circulate a fluid to carry away the heat.  The only difference is that the cooling system is total-loss.  The heated fluid is allowed to expand out the nozzle to provide thrust, instead of circulating back through the core.

The NSWR is completely different in basic concept from any of the above.  It has no solid fuel core around which a fluid passes.  Instead, the uranium is dissolved in the water.  That's where the "nuclear saltwater" part of the name comes from.  This water is stored in such a way that the uranium in it is prevented from reaching critical mass until it enters the combustion chamber.  Once in the combustion chamber, the uranium heats up, boiling the water and shooting both itself and the steam out the nozzle.

This sounds all very nice in theory, but the rub is storing the nuclear saltwater.  You can't have it in a single big tank or the uranium in it would go critical in the tank, just as it does in the combustion chamber, and the ship would explode.  About the only way anybody can think of to store the fuel is in a great mass of very long, very small-diameter tubes made of and/or separated by some neutron-absorbing material.  IOW, the fuel tank configuration would resemble the core of a conventional reactor, with the tubes of nuclear saltwater being analogous to the solid fuel rods, and the neutron-absorbing stuff between them being analogous to the control rods.  So basically, the fuel tank itself (not the actual engine) would essentially be a nuclear reactor core in full SCRAM mode.

Now think of what that implies for the ship just sitting still.  First, there's the mass of fuel as uranium is heavy.  Then there's the mass of all the neutron-absorbing stuff, which is also very heavy.  And the whole thing is still giving off radiation and making heat even when the engine's not running, so needs both shielding around the outside AND its own cooling system to carry off the waste heat that will always be happening.  And all this stuff has to be very small-diameter, which makes it both problematic to manufacture, hugely expensive, and not having much margin for the normal erosion of materials when exposed to neutrons.  Also, if you build an NSWR ship in orbit, all the tankers sent to fuel it up will have to be build the same way, and have even more shielding because it'll be on the ground to start with.  And of the tanker crashes on launch, you end up with a big pile of uranium going critical with no shielding at all.

Now think about how this would work with the engine running.  First, you have to come up with some system to force the nuclear saltwater out of the long, skinny tubes you have to store it in.  This is going to take quite a bit of pushing because there'll be so much friction loss in the long, small-diameter tubes, yet the pressure can't be very high or the skinny tubes will rupture.  And you'll need scads of such pumps, 1 for each of the myriad of fuel tubes., so way more weight and complexity.  But if you do somehow get the engine running, you create thrust, which will cause the heavy uranium to be centrifuged down to the bottom of the tubes instead of remaining uniformly distributed in solution.  This could result in the fuel going critical at the bottom ends of the tubes.  At the very least, it will screw up the ratio of uranium to water, making it too rich to start with and too lean later.

Now think about the maintenance problem of all this.  All the tubes and the neutron-absorbing stuff will have to be replaced frequently because they'll erode.  All those pumps will need frequent care, too.  But the big operational problem is how to deal with fuel leaks.  You have thousands of tubes, all rather long, no doubt made in multiple sections.  They could each leak anywhere along their lengths.  But they're densely packed so you can't access any but the outer layer of tubes.  So, if you get a leak in one of the interior tubes, it'll be spraying uranium all over the area.  The water boils away in the vacuum and you're left with uranium icicles, which will go critical as they're out of their neutron-absorbing sheaths.  This will burn bigger holes in other tubes, allowing more uranium build-up, resulting eventually in the whole tank exploding.

This is what makes the whole NSWR idea so crazy.  The very property of the nuclear saltwater which makes it work (in theory) as a rocket fuel also prevents any workable way to store the stuff or transport the fuel.

Link to comment
Share on other sites

25 minutes ago, Geschosskopf said:

Um, no..    Not.  At.  All.  The NSWR has NOTHING in common with a normal (or even molten salt) reactor, other than they both involve uranium.  Thus, the challenges are ENTIRELY different.

In the conventional reactors you mention, the uranium is solid, in the fuel rods, and doesn't move.  The pressurized water or molten salt is merely coolant, absorbing heat from the solid core and carrying it away to keep it from melting.  As this fluid circulates through the fuel rods, it picks up bits of radioactive solids so is usually not the actual working fluid---otherwise you'd contaminate the turbines, which would complicate maintenance.  So instead, the coolant goes through a heat-exchanger to pass the heat on to the actual working fluid, which is water in a separate set of pipes.  This water turns to steam, spins the turbines to make electricity, condenses, gets cooled in the big towers, and back into the heat exchanger.

A NERVA is essentially a conventional reactor just like the above.  You still have a solid fuel core around which you circulate a fluid to carry away the heat.  The only difference is that the cooling system is total-loss.  The heated fluid is allowed to expand out the nozzle to provide thrust, instead of circulating back through the core.

The NSWR is completely different in basic concept from any of the above.  It has no solid fuel core around which a fluid passes.  Instead, the uranium is dissolved in the water.  That's where the "nuclear saltwater" part of the name comes from.  This water is stored in such a way that the uranium in it is prevented from reaching critical mass until it enters the combustion chamber.  Once in the combustion chamber, the uranium heats up, boiling the water and shooting both itself and the steam out the nozzle.

This sounds all very nice in theory, but the rub is storing the nuclear saltwater.  You can't have it in a single big tank or the uranium in it would go critical in the tank, just as it does in the combustion chamber, and the ship would explode.  About the only way anybody can think of to store the fuel is in a great mass of very long, very small-diameter tubes made of and/or separated by some neutron-absorbing material.  IOW, the fuel tank configuration would resemble the core of a conventional reactor, with the tubes of nuclear saltwater being analogous to the solid fuel rods, and the neutron-absorbing stuff between them being analogous to the control rods.  So basically, the fuel tank itself (not the actual engine) would essentially be a nuclear reactor core in full SCRAM mode.

Now think of what that implies for the ship just sitting still.  First, there's the mass of fuel as uranium is heavy.  Then there's the mass of all the neutron-absorbing stuff, which is also very heavy.  And the whole thing is still giving off radiation and making heat even when the engine's not running, so needs both shielding around the outside AND its own cooling system to carry off the waste heat that will always be happening.  And all this stuff has to be very small-diameter, which makes it both problematic to manufacture, hugely expensive, and not having much margin for the normal erosion of materials when exposed to neutrons.  Also, if you build an NSWR ship in orbit, all the tankers sent to fuel it up will have to be build the same way, and have even more shielding because it'll be on the ground to start with.  And of the tanker crashes on launch, you end up with a big pile of uranium going critical with no shielding at all.

Now think about how this would work with the engine running.  First, you have to come up with some system to force the nuclear saltwater out of the long, skinny tubes you have to store it in.  This is going to take quite a bit of pushing because there'll be so much friction loss in the long, small-diameter tubes, yet the pressure can't be very high or the skinny tubes will rupture.  And you'll need scads of such pumps, 1 for each of the myriad of fuel tubes., so way more weight and complexity.  But if you do somehow get the engine running, you create thrust, which will cause the heavy uranium to be centrifuged down to the bottom of the tubes instead of remaining uniformly distributed in solution.  This could result in the fuel going critical at the bottom ends of the tubes.  At the very least, it will screw up the ratio of uranium to water, making it too rich to start with and too lean later.

Now think about the maintenance problem of all this.  All the tubes and the neutron-absorbing stuff will have to be replaced frequently because they'll erode.  All those pumps will need frequent care, too.  But the big operational problem is how to deal with fuel leaks.  You have thousands of tubes, all rather long, no doubt made in multiple sections.  They could each leak anywhere along their lengths.  But they're densely packed so you can't access any but the outer layer of tubes.  So, if you get a leak in one of the interior tubes, it'll be spraying uranium all over the area.  The water boils away in the vacuum and you're left with uranium icicles, which will go critical as they're out of their neutron-absorbing sheaths.  This will burn bigger holes in other tubes, allowing more uranium build-up, resulting eventually in the whole tank exploding.

This is what makes the whole NSWR idea so crazy.  The very property of the nuclear saltwater which makes it work (in theory) as a rocket fuel also prevents any workable way to store the stuff or transport the fuel.

 

LOL. I tend to agree. Even thermonuclear pusher plate propulsion sounds safer and more reliable compared to this.

At least you do not have to worry about your vessel exploding due to a chemical mishap. As nuclear bombs are designed to only blow up under specific circumstances.

Edited by Spacescifi
Link to comment
Share on other sites

1 hour ago, Geschosskopf said:

Um, no..    Not.  At.  All.  The NSWR has NOTHING in common with a normal (or even molten salt) reactor, other than they both involve uranium.

Yes, I am aware. You need not inform me of the difference between pressurized reactors, molten salt reactors, and a NSWR.

1 hour ago, Geschosskopf said:

Thus, the challenges are ENTIRELY different.

No, not necessarily.

You go on to list many of the very real challenges, which are readily acknowledged. They are by no means solved. But they are not significantly more challenging than the early materials and engineering hurdles for pressurized nuclear reactors. They are different challenges, obviously, but they are not dramatically more different. It is nothing whatsoever like the challenges in creating a Halo drive, for example.

Link to comment
Share on other sites

8 minutes ago, sevenperforce said:

Yes, I am aware. You need not inform me of the difference between pressurized reactors, molten salt reactors, and a NSWR.

No, not necessarily.

You go on to list many of the very real challenges, which are readily acknowledged. They are by no means solved. But they are not significantly more challenging than the early materials and engineering hurdles for pressurized nuclear reactors. They are different challenges, obviously, but they are not dramatically more different. It is nothing whatsoever like the challenges in creating a Halo drive, for example.

I am glad he explained it for those not familiar with NSWR. Like me.

I still think project Orion is better than NSWR.

They are both radioactive, but at least project orion has less points of failure.

With NSWR, the possible points of catastrophic failure are multiplied tenfold. And for what?

Performance and thrust I doubt are dramatically better than an orion pusher plate, at the cost of multiple complicated possible points of failure.

Edited by Spacescifi
Link to comment
Share on other sites

14 minutes ago, Nothalogh said:

Just a cursory look at even the worst case ISP and TWR should tell you exactly "for what".

For pete's sake, you could put a probe in the outer solar system in a few months, with one of these pushing it.

 

Okay

 So if we could engineer it to work it would make great probe? Good... but I want human crewes spaceships.

Scaling it up for a spaceship with a human crew sounds rather dangerous.

For a human crew I think old boom-boom is better.

Link to comment
Share on other sites

27 minutes ago, Spacescifi said:

Okay

 So if we could engineer it to work it would make great probe? Good... but I want human crewes spaceships.

Scaling it up for a spaceship with a human crew sounds rather dangerous.

For a human crew I think old boom-boom is better.

One of the nice things about NSWRs is that if something DOES go horribly wrong, it becomes an impromptu single-pulse Orion. So structure your vehicle accordingly, and you're fine.

Link to comment
Share on other sites

This thread is quite old. Please consider starting a new thread rather than reviving this one.

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...