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Best Spaceship We Could Build Now


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Nuclear saltwater rockets can actually be made much smaller than orion drives, as like minmags they are not limited to the minimum size of self contained explosives.

Regarding specific impulses: Pure fission Orion can have isps between 1800-4500s, Thermonuclear Orion can push this up to 7500-12000s, MinMag Orion can do 9500-16000s, NSWRs can do 4000-8000s (though I've also seen values of 67000s and 482000s)

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59 minutes ago, Bill Phil said:

Saltwater isn't the best choice. The reason it works for nuclear salt water is that the specific salt used contains fissile material, and is not the same kind of saltwater found in Earth's oceans. Either use normal water or some other propellant.

Yep. If you have a bunch of antimatter laying around then your best route to orbit and beyond is probably a LOX-afterburning liquid-hydrogen antimatter-thermal rocket. 

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45 minutes ago, wafflemoder said:

Nuclear saltwater rockets can actually be made much smaller than orion drives, as like minmags they are not limited to the minimum size of self contained explosives.

Regarding specific impulses: Pure fission Orion can have isps between 1800-4500s, Thermonuclear Orion can push this up to 7500-12000s, MinMag Orion can do 9500-16000s, NSWRs can do 4000-8000s (though I've also seen values of 67000s and 482000s)

Pure fission Orion can potentially reach 12000s. This is because the bomb yield per kilogram actually improves with higher bomb masses.

Mini-Mag can reach 16000s, yes, but it can actually exceed 20000s and likely 30000s if fusion boosting is used (increasing the fission burnup rate). 

I've never seen anything to indicate NSWR ISP that high, though if it does exist the temperature would be immense and would require magnetic confinement, and potentially have low thrust unless you have really good radiators.

Edited by Bill Phil
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I've only ever seen Orion figures above 10000s when using thermonuclear hydrogen bombs, which do get really efficient with size. Pure fission weapons are pretty terrible, which is why they were quickly superseded by thermonuclear weapons.

Looking through some of the papers on Mini-Mag Orion, they seem to top off at 25000s using Curium 245 as the fissile material, with values around half that for plutonium and uranium based charges.

The 482 ks value for NSWR probably represents the theoretical maximum, in much the same way H-bomb orion can have a  theoretical maximum ISP of 100 ks.

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25 minutes ago, wafflemoder said:

I've only ever seen Orion figures above 10000s when using thermonuclear hydrogen bombs, which do get really efficient with size. Pure fission weapons are pretty terrible, which is why they were quickly superseded by thermonuclear weapons.

Looking through some of the papers on Mini-Mag Orion, they seem to top off at 25000s using Curium 245 as the fissile material, with values around half that for plutonium and uranium based charges.

The 482 ks value for NSWR probably represents the theoretical maximum, in much the same way H-bomb orion can have a  theoretical maximum ISP of 100 ks.

The Mini-Mag Orion papers don't use fusion boosting in the pulse units - which would boost the fission yield significantly. Many fission bombs do the same. They do use a small amount of fusion for the initial neutron source, but not a large amount.

Fusion boosting is essentially having a hollow fissile core with fusion fuel inside that undergoes fusion during the explosion - releasing more neutrons and thus causing more fission. This would benefit Mini-Mag quite well. The papers assume a 10% burnup fraction for the Curium target - this can be theoretically increased much more, likely to 30% or even 40%. This would greatly increase the available energy, and thus the specific impulse. 

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2 hours ago, Bill Phil said:

Nuclear Saltwater doesn't actually perform as well as Orion, depending on the chosen Orion vehicle. Remember, NSWR gets around 6000 seconds of ISP, and advanced Orions can easily double that assuming the original papers were correct. It may be possible to improve NSWR performance, but it's also possible to improve Orion performance. And it certainly doesn't outperform Mini-Mag, which is theoretically capable of even higher ISP if it used fusion boosting.

It's also much more difficult to build - at least Orions don't try to actually contain their nuclear detonations or if they do they use magnetic nozzles and much, much smaller detonations.

Those are methods of getting stuff into space, not actual space vehicles. That said, they're vastly superior to rockets in many ways, provided we actually build them. But we don't call seaports ocean-going ships. Infrastructure is not the same as a vehicle - at least for now. Orbital skyhooks and other such things do combine vehicles with infrastructure.

Your question is what is the best we could build now. And the best we could build now just can't do that. Even Mini-Mag is stretching the "now" part a bit far. Now, theoretically, if we could build gas-core fission rockets then we can have closed cycle gas core rockets for landing and some kind of Z-Pinch drive like Mini-Mag for space. You don't need much delta-V since the Mini-Mag can slow you down over the target - maybe 2 km/s.

Basically two engine systems:

1.) Closed Cycle Gas Core NTR: Take off and landing

2.) Fusion Boosted Mini-Mag Orion: Finalizing orbit and some in-space maneuvering

This vehicle would suffer the worst of both worlds, however, as it would need to stow its space drives and other things to land. A separate dedicated landing vehicle would be far more appropriate.

Now if you just want to take off and land and use some other system to get around space itself and not a realistic drive, you can just use number 1 above.

1.) This thread is about the now. Antimatter is out of the question except for - and this is a very big stretch - antimatter initiated nuclear systems.

2.) Saltwater isn't the best choice. The reason it works for nuclear salt water is that the specific salt used contains fissile material, and is not the same kind of saltwater found in Earth's oceans. Either use normal water or some other propellant.

3.) Anti-iron is even more difficult than anti-hydrogen and has worse performance than electron-positron annihilation because you will not get perfect annihilation due to the more complex atom.

 

1. Yes. And I still chose to go further since apparently modern technology will only allow a rocket to takeoff to orbit and reenter at leisure if it has minimal to no payload, and what payload there is is for ISRU equipment to crack LH and LOX from ocean water upon landing on a beach. Maybe a nuclear reactor would help, I dunno, but the scifi dream of a spaceship that can come and go simply by refueling off water and taking off again is farfetched and difficult. But not impossible... just might not be worth it due to small payloads.

2. I am well read and know about the uranium salts for the Nuclear Salt Water Rocket. I only chose saltwater because it is abundant, and I know it is a poor propellant choice. Why do you think I chose AM thermal to augment it? Because I figured that nuclear would not havd the needed thrust to make a difference about reaching orbit. But people are aware of the vast power of AM. Now assuming even that is not good enough because saltwater is that poor of a get to orbit propellant, onboard machines might take days or weeks to split LH and LOX from ocean water to fill propellant tanks.

And then, with AM it surely would get back to space. Just takes days or weeks of propellant processing. That's all.

 

See... I am interested in a spaceship that can land on an alien Earth, refuel with water, and takeoff to orbit again.

 

3. Perhaps. But the limits of modern science have forced my hand. So I am just leaving it to the future to figure out the details of anti-iron. Even so, I am sure there is a way to get full annihilation of it... even if we don't know how. Scifi need not explain how to do what even scientists can't do. If I could do that I should be richer than Elon.

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If you're looking for theoretically plausible options, than magnetic monopole catalyzed nucleon conversion, or Q-ball antimatter mirrors are really good options.

Essentially monopoles can force protons and neutrons to decay into pions and positrons, which can further decay into muons, neutrinos, and gamma rays. The end result is nearly identical to matter-antimatter annihilation. What makes 'conversion' systems better than antimatter is that magnetic monopoles are not consumed in the reaction, so as long as propellant is available (which can be anything from hydrogen to literal dirt) the drive can operate indefinitely, without additional monopoles being required. You could also make a monopole conversion ramjet,  a more feasible variant of the bussard fusion ramjet, which uses monopoles to convert interstellar or interplanetary gas directly into energy, giving you essentially unlimited range and top speeds of very high fractions (30-80%) of lightspeed.

In addition to this, the magnetic monopoles are far easier to store than antimatter and you would need to store less of it. Magnetic monopoles only convert matter (at reasonable rates) in high temperature conditions, allowing for it to be stored bound to regular matter. These could be used in any applications antimatter could, with only slightly reduced performance for far safer and more manageable fuels. One of the best resources for information on Magnetic monopole propulsion is The Orion's Arm Universe Project, which is a very realistic sci-fi setting.

Q-balls can also be used for effective propulsion, in more ways than one. Q-balls are a hypothetical particles (?) and dark matter candidate than can "reflect" any matter it comes into contact with into antimatter for zero energy (in fact the Q-ball actually gains energy but we'll get to that). This allows for Q-balls to be used in a 'mirror' converting some fraction of a crafts propellant into antimatter for propulsion. This is really convenient as it also allows for you to both work around antimatter storage and allow it to be trivially created in situ from any materials. Much like the magnetic monopoles mentioned earlier, this can be used as a ramscoop to allow for (nearly) unlimited range.

As mentioned, Q-balls actually gain energy when converting matter into antimatter. Apparently they draw it from the quantum vacuum (not entirely sure myself). A single Q-ball can convert ~8000 tons of matter to antimatter before becoming fully charged (unable to convert any more matter), gaining ~31 grams of mass in the process. The real kicker is that these charged q-balls, despite only massing 31 grams, actually have 8000 tons of mass-energy, meaning that they can store 260 million times more energy per kilogram than antimatter. Now there probably isn't a way to harness this energy, but if there was, it would allow for ridiculously efficient craft. Again, Orion's Arm also has a fair deal of information regarding "Q-Mirrors" and "Q-Batteries", though there are also several scientific papers floating around about the interesting properties of Q-balls.

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38 minutes ago, wafflemoder said:

If you're looking for theoretically plausible options, than magnetic monopole catalyzed nucleon conversion, or Q-ball antimatter mirrors are really good options.

Essentially monopoles can force protons and neutrons to decay into pions and positrons, which can further decay into muons, neutrinos, and gamma rays. The end result is nearly identical to matter-antimatter annihilation. What makes 'conversion' systems better than antimatter is that magnetic monopoles are not consumed in the reaction, so as long as propellant is available (which can be anything from hydrogen to literal dirt) the drive can operate indefinitely, without additional monopoles being required. You could also make a monopole conversion ramjet,  a more feasible variant of the bussard fusion ramjet, which uses monopoles to convert interstellar or interplanetary gas directly into energy, giving you essentially unlimited range and top speeds of very high fractions (30-80%) of lightspeed.

In addition to this, the magnetic monopoles are far easier to store than antimatter and you would need to store less of it. Magnetic monopoles only convert matter (at reasonable rates) in high temperature conditions, allowing for it to be stored bound to regular matter. These could be used in any applications antimatter could, with only slightly reduced performance for far safer and more manageable fuels. One of the best resources for information on Magnetic monopole propulsion is The Orion's Arm Universe Project, which is a very realistic sci-fi setting.

Q-balls can also be used for effective propulsion, in more ways than one. Q-balls are a hypothetical particles (?) and dark matter candidate than can "reflect" any matter it comes into contact with into antimatter for zero energy (in fact the Q-ball actually gains energy but we'll get to that). This allows for Q-balls to be used in a 'mirror' converting some fraction of a crafts propellant into antimatter for propulsion. This is really convenient as it also allows for you to both work around antimatter storage and allow it to be trivially created in situ from any materials. Much like the magnetic monopoles mentioned earlier, this can be used as a ramscoop to allow for (nearly) unlimited range.

As mentioned, Q-balls actually gain energy when converting matter into antimatter. Apparently they draw it from the quantum vacuum (not entirely sure myself). A single Q-ball can convert ~8000 tons of matter to antimatter before becoming fully charged (unable to convert any more matter), gaining ~31 grams of mass in the process. The real kicker is that these charged q-balls, despite only massing 31 grams, actually have 8000 tons of mass-energy, meaning that they can store 260 million times more energy per kilogram than antimatter. Now there probably isn't a way to harness this energy, but if there was, it would allow for ridiculously efficient craft. Again, Orion's Arm also has a fair deal of information regarding "Q-Mirrors" and "Q-Batteries", though there are also several scientific papers floating around about the interesting properties of Q-balls.

 

Hmmm. I do appreciate your effort to help but.... this is beyond my comprehension, and even though I could figure it out it seems theoretical, meaning we don't know if magnetic monopoles exist or if they can. Same goes for the Q-balls.

Unlike antimatter.

Overall, orion's arm gets far more into detail than I ever will in my scifi. I am far more interested in how technology effects the characters.

 

Meaning I like to explore the implications of a said technology on societiy more than how it works.

 

 

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That's totally understandable. You can probably further justify whatever propulsion system you choose to use, even ones that are very obviously obsolete or problematic, with legal nonsense. I could totally see a megacorp or the like copyrighting the idea of fusion or antimatter drives, forcing unaffiliated parties into using orion drives instead.

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2 hours ago, Spacescifi said:

I figured that nuclear would not havd the needed thrust to make a difference about reaching orbit. But people are aware of the vast power of AM. Now assuming even that is not good enough because saltwater is that poor of a get to orbit propellant

The difference between a nuclear saltwater rocket and an antimatter rocket is NOT an issue of poor thrust on the latter's part.

AM still needs propellant.

Saltwater is much better as a "get to orbit" propellant than hydrogen, if you're heating it up at antimatter levels.

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17 minutes ago, wafflemoder said:

That's totally understandable. You can probably further justify whatever propulsion system you choose to use, even ones that are very obviously obsolete or problematic, with legal nonsense. I could totally see a megacorp or the like copyrighting the idea of fusion or antimatter drives, forcing unaffiliated parties into using orion drives instead.

 

Haha... at this point all I see is that known quanities of stuff we have and could make if we had more (antimatter) don't fit the bill for my scifi.

For example, my scifi will explore civilizations where space travel is common as air passenger jet flight.

Interplanetary and interstellar in reasonable time requires totally fictional stuff I make up for plot. Insert fictional drive here, but not without rules and limits. For example, the hyper drive can put a ship near any planet with 1g or greater. Anything less they can only thrust via constant acceleration to. Meaning it would take a few hours to reach the moon, but they could reach Mars in about a minute or so... just have to find what represents it in the huge hyperspace room first. Which is easy if they have done it before. Hyperspace is a system of tunnels (pathways to other solar systems) and rooms (what represents a solar system).

 

2 minutes ago, sevenperforce said:

The difference between a nuclear saltwater rocket and an antimatter rocket is NOT an issue of poor thrust on the latter's part.

AM still needs propellant.

Saltwater is much better as a "get to orbit" propellant than hydrogen, if you're heating it up at antimatter levels.

 

Okay...what kind of plume should I expect to show the reader?

I want scientific accuracy there at least.

 

 

Is it a long plume of white steam?

Or just bluish white fiery exhaust?

Or both?

Edited by Spacescifi
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Now that have a slightly better handle on what your aiming for, here's a shortlist of what might work in your setting for planetary operations, and my best guess of performance and what they might look like.

The Nuclear (Fission) Options:

  • Liquid Core Fission Rocket (Open Cycle): Very good TWR, but lower ISP. Liquid fissiles mix with and heat hydrogen propellant. Most fissiles are kept within the reactor, but some can escape, possibly bad for occupied worlds. ISP of 1000-2000s, engine TWR of 8~50. Bright translucent white exhaust. No residual smoke or steam trail.
  • Gas Core Fission Rocket (Open Cycle): Similar to Liquid cores, but fissiles heated to a gas for increased efficiency. Fissiles escape more easily than liquid cores, possibly bad for occupied worlds. ISP of 3000-7000s, engine TWR of 5~20. Bright translucent blue exhaust, with subtle hints of magenta from hydrogen plasma. No residual smoke or steam trail.
  • Gas Core Fission Rocket (Closed Cycle): Similar to above, but fissiles and hydrogen are kept separate, at the cost of added complexity and reduced performance. Not intrinsically bad for occupied worlds. ISP of 1500-3000s, engine TWR of 2~15. Bright translucent blue-white exhaust. No residual smoke or steam trail.
  • Salt Water Nuclear Rocket (Very Open Cycle): Liquid Fallout, very very bad for inhabited worlds. ISP of 4000-10000+, TWR of 10~40?. Very bright translucent blue exhaust, with hints of magenta from hydrogen plasma. Residual trail of white-light grey steamy clouds.

External Fission and Fission/Fusion Pulse systems are a poor choice for planetary use for reasons already discussed, so wouldn't be a fit for the setting imo.

Fusion isn't well suited for planetary use either. ICF and MIF systems suffer similar problems to other pulsed propulsion systems, but with lower TWRs in favor of much higher ISPs. MCF systems have very poor TWRs but fantastic ISP. You can thrust augment a Fusion drive with "afterburners" (injecting additional propellant to increase thrust at the expense of fuel economy), but this results in worse performances than fission thermal rockets.

Antimatter Options: (probably the better choice for an FTL capable society)

  • Liquid Core AM Thermal: Cleaner than fission, antimatter annihilates before it can escape, but some x-rays can be emitted. Pretty safe. ISP of 1500-2500s, engine TWR of 10-40. Bright blue-white exhaust
  • Gas Core AM Thermal: Uses more antimatter than liquids. Emits some x-rays and gamma, but otherwise fairly safe. ISP 4000-10000s, TWR 3-10. Bright blue-indigo? exhaust. No trail
  • Fusion augmented AM Gas Core: Using deuterium in addition to hydrogen. Less antimatter is needed and x-ray emissions are reduced. Safe. ISP 3000-7000, TWR 3-10. Bright blue-indigo? exhaust. No trail

Any higher power antimatter systems aren't well geared for planetary use, and put out significant amounts of x-rays and gamma.

As for how you could handle your FTL PlotdriveProject Rho has a page for designing FTL in fiction which might be a useful resource.

Edited by wafflemoder
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9 hours ago, wafflemoder said:

Now that have a slightly better handle on what your aiming for, here's a shortlist of what might work in your setting for planetary operations, and my best guess of performance and what they might look like.

The Nuclear (Fission) Options:

  • Liquid Core Fission Rocket (Open Cycle): Very good TWR, but lower ISP. Liquid fissiles mix with and heat hydrogen propellant. Most fissiles are kept within the reactor, but some can escape, possibly bad for occupied worlds. ISP of 1000-2000s, engine TWR of 8~50. Bright translucent white exhaust. No residual smoke or steam trail.
  • Gas Core Fission Rocket (Open Cycle): Similar to Liquid cores, but fissiles heated to a gas for increased efficiency. Fissiles escape more easily than liquid cores, possibly bad for occupied worlds. ISP of 3000-7000s, engine TWR of 5~20. Bright translucent blue exhaust, with subtle hints of magenta from hydrogen plasma. No residual smoke or steam trail.
  • Gas Core Fission Rocket (Closed Cycle): Similar to above, but fissiles and hydrogen are kept separate, at the cost of added complexity and reduced performance. Not intrinsically bad for occupied worlds. ISP of 1500-3000s, engine TWR of 2~15. Bright translucent blue-white exhaust. No residual smoke or steam trail.
  • Salt Water Nuclear Rocket (Very Open Cycle): Liquid Fallout, very very bad for inhabited worlds. ISP of 4000-10000+, TWR of 10~40?. Very bright translucent blue exhaust, with hints of magenta from hydrogen plasma. Residual trail of white-light grey steamy clouds.

External Fission and Fission/Fusion Pulse systems are a poor choice for planetary use for reasons already discussed, so wouldn't be a fit for the setting imo.

Fusion isn't well suited for planetary use either. ICF and MIF systems suffer similar problems to other pulsed propulsion systems, but with lower TWRs in favor of much higher ISPs. MCF systems have very poor TWRs but fantastic ISP. You can thrust augment a Fusion drive with "afterburners" (injecting additional propellant to increase thrust at the expense of fuel economy), but this results in worse performances than fission thermal rockets.

Antimatter Options: (probably the better choice for an FTL capable society)

  • Liquid Core AM Thermal: Cleaner than fission, antimatter annihilates before it can escape, but some x-rays can be emitted. Pretty safe. ISP of 1500-2500s, engine TWR of 10-40. Bright blue-white exhaust
  • Gas Core AM Thermal: Uses more antimatter than liquids. Emits some x-rays and gamma, but otherwise fairly safe. ISP 4000-10000s, TWR 3-10. Bright blue-indigo? exhaust. No trail
  • Fusion augmented AM Gas Core: Using deuterium in addition to hydrogen. Less antimatter is needed and x-ray emissions are reduced. Safe. ISP 3000-7000, TWR 3-10. Bright blue-indigo? exhaust. No trail

Any higher power antimatter systems aren't well geared for planetary use, and put out significant amounts of x-rays and gamma.

As for how you could handle your FTL PlotdriveProject Rho has a page for designing FTL in fiction which might be a useful resource.

Thank you.

Do any of these work with plain saltwater?

Because refueling by splitting hydtogen will take time. Hours or days.

Like I know I know the payload will be small.

It is ironic really. Using a big rocket to filled witu water to lift six crew off a planet!

No such thing as small shuttlecraft IRL using rocketry! Because of several factorsm

Edited by Spacescifi
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As none of them are chemical based, pretty much any fluid propellant can be used, with the exceptions of nuclear saltwater rockets and fusion augmented antimatter. Internal plumbing would have to be tailored to a certain propellant though (no jury rigging an H2O fueled craft to use O2, or at least not easily). The propellant used would affect the ISP and engine power with higher molar mass particles generally giving lower thrust and ISP.

Some propellant processing will be required though, to remove any materials that could cause blockages in the plumbing where temperatures aren't 5000+ Kelvin. Salts, metals, and carbon soot would be the biggest offenders, remaining solid while the more volatile components are evaporated. Some propellants may also chemically react with the engine itself, oxidizing, corroding or otherwise jeopardizing the integrity of the engine. Halogens and Chalcogens like bromine, oxygen, sulfur, chlorine and especially fluorine should be avoided because of this. For this reason propellants would still need to be processed (often quite heavily), but could be sped up significantly by the shear power available from these spacecraft (The mainsail's description of being able to power a small nation isn't that far off the mark). Resource extraction would still take some time though, especially for larger craft. Distilled water would probably be your go to for exploration vessels in locations without the infrastructure in place to refuel with hydrogen. More civilized areas would probably stick with hydrogen though.

Some of the more favorable and abundant propellants (ordered roughly by efficiency):

H2, He, NH3, H2O, Ne, N2, O2?, Ar, CO2?

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In terms of shuttle craft, there should be a lot of options available (I'm assuming shuttles are non-FTL craft primarily for ferrying small crews or payloads to and from planets and moons with various masses and atmospheres)

With how large your ships are, you could probably get away with having a few types of shuttles for various purposes and/or of various sizes. If the technology is available, you could have smart ships that reconfigure themselves for a specific task. Shuttle craft probably wouldn't be needed (but nice to have) for more developed worlds with extensive orbital infrastructure in place, or smaller moons like those of saturn and uranus (excluding titan), where gravity and dV are minimal.

Main categories I can think of are moon-mars sized (atmosphere is negligible), earth-superearth sized (low pressure), and earth-superearth sized (high pressure).

...and now I want to design a family of shuttle vehicles for an assortment of planetary environments of 5-10 crew/20t payload (space shuttle like) and 25-50 crew/100t payload (starship like)

Any prefered propulsion system for shuttle craft.

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2 hours ago, wafflemoder said:

 

...and now I want to design a family of shuttle vehicles for an assortment of planetary environments of 5-10 crew/20t payload (space shuttle like) and 25-50 crew/100t payload (starship like)

Any prefered propulsion system for shuttle craft.

I am concerned that saltwater AM thermal won't be efficient enough to loft a 100 ton payload to orbit.... and if it did, the ship would be big.... probably bigger than Elon's Starship.

Splitting into better fuel processing seems inevitable.

3 hours ago, wafflemoder said:

As none of them are chemical based, pretty much any fluid propellant can be used, with the exceptions of nuclear saltwater rockets and fusion augmented antimatter. Internal plumbing would have to be tailored to a certain propellant though (no jury rigging an H2O fueled craft to use O2, or at least not easily). The propellant used would affect the ISP and engine power with higher molar mass particles generally giving lower thrust and ISP.

Some propellant processing will be required though, to remove any materials that could cause blockages in the plumbing where temperatures aren't 5000+ Kelvin. Salts, metals, and carbon soot would be the biggest offenders, remaining solid while the more volatile components are evaporated. Some propellants may also chemically react with the engine itself, oxidizing, corroding or otherwise jeopardizing the integrity of the engine. Halogens and Chalcogens like bromine, oxygen, sulfur, chlorine and especially fluorine should be avoided because of this. For this reason propellants would still need to be processed (often quite heavily), but could be sped up significantly by the shear power available from these spacecraft (The mainsail's description of being able to power a small nation isn't that far off the mark). Resource extraction would still take some time though, especially for larger craft. Distilled water would probably be your go to for exploration vessels in locations without the infrastructure in place to refuel with hydrogen. More civilized areas would probably stick with hydrogen though.

Some of the more favorable and abundant propellants (ordered roughly by efficiency):

H2, He, NH3, H2O, Ne, N2, O2?, Ar, CO2?

 

How does one go about the process of filtering out alien fish, crabs, or octopus that get sucked up up while sucking water out thr ocean?

What? Let machines do it?

At some point I am betting the crew will have to roll up their sleeves and get the pipe and clean it.

So not only must their plumbing work,  it must be designed for ease of cleaning by the crew.

Edited by Spacescifi
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Properly cooked sealife efficiently turns into water, carbon dioxide, nitrogen, and small amount of lime.

P.S.
The octopus is a thing. It's a ready to use pellet for thermal propulsion. Though jellyfishes give more pure exhaust.

For crabs they have the special tool.

Spoiler

71W9xO7eKoL._AC_SX522_.jpg

 

P.P.S.
Lemme suggest a topic for the next thread: "How to protect your pusher plate from fouling."

Edited by kerbiloid
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2 hours ago, Spacescifi said:

I am concerned that saltwater AM thermal won't be efficient enough to loft a 100 ton payload to orbit.... and if it did, the ship would be big.... probably bigger than Elon's Starship.

No worries there. Here's a "basic" rundown of what a water propelled AM Gas Core SSTO could look like. 

My assumptions:

  • 16000 m/s of dV.
  • Upright landing, change height to length if sideways landing is desired (doesn't make any real difference)
  • 8 meter diameter rocket, height determined by tankage volume. Additional 8 meters in height from engines, and 25 meters in height from payload bay.
  • 100t payload + 10t for misc structural and avionics.
  • Water: 0.8 kg/L in tankage. Tankage mass is 5% the propellant mass. (95.3% propellant)
  • Antiprotons: 0.01 kg/L in tankage. Tankage mass is 10000% the fuel mass. (1% fuel)
  • Water:Antiproton mass ratio = 1,000,000:1 (used at a rate of 10,000,000:1, allowing for 10 water refuelings before additional antimatter is required)
  • Vacuum ISP = 2400s, sea level ISP = 1600s. Engine vacuum TWR = 6. Engine sea level TWR = 4.
  • Minimum allowable surface TWR: 1.4

Calculated values: (masses calculated after payload mass fraction is known)

  • Combined reaction mass (water+antiprotons): ~0.8kg/L in tankage. Tank mass is 5.1% the reaction mass. (95.1% reaction mass)
  • Gross mass/dry loaded mass: 1.9731        = 835.4 t
  • Tankage mass/dry loaded mass: 0.0496  = 21 t
  • Engine mass/dry loaded mass: 0.6906     = 292.4 t
  • Payload mass/dry loaded mass: 0.2362.  = 100 t
  • Misc structural mass: 0.0236                      = 10 t
  • Dry empty mass:                                            = 323.4 t
  • Water propellant mass                                  = 412 t
  • Antiproton fuel mass                                     = ~0.41 kg
    • Total vacuum (sea level) thrust: 17.21 (11.47) MN
    • Total height: 43.3 meters
  • dV (no payload): 19340 m/s
  • (no payload) Vacuum (Sea level) TWR: 2.39 (1.59)
    • Time to fill by US fire hydrant (500-1500 gal/min): 1.2 to 3.6 hours
    • Time to fill by average garden hose (17 gal/min): 4.44 days

For comparison, Starship (just the upper stage) has a 9 meter diameter, is 50 meters tall, and weighs ~1420 tons fully fueled with payload.

Edited by wafflemoder
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5 hours ago, wafflemoder said:

No worries there. Here's a "basic" rundown of what a water propelled AM Gas Core SSTO could look like. 

My assumptions:

  • 16000 m/s of dV.
  • Upright landing, change height to length if sideways landing is desired (doesn't make any real difference)
  • 8 meter diameter rocket, height determined by tankage volume. Additional 8 meters in height from engines, and 25 meters in height from payload bay.
  • 100t payload + 10t for misc structural and avionics.
  • Water: 0.8 kg/L in tankage. Tankage mass is 5% the propellant mass. (95.3% propellant)
  • Antiprotons: 0.01 kg/L in tankage. Tankage mass is 10000% the fuel mass. (1% fuel)
  • Water:Antiproton mass ratio = 1,000,000:1 (used at a rate of 10,000,000:1, allowing for 10 water refuelings before additional antimatter is required)
  • Vacuum ISP = 2400s, sea level ISP = 1600s. Engine vacuum TWR = 6. Engine sea level TWR = 4.
  • Minimum allowable surface TWR: 1.4

Calculated values: (masses calculated after payload mass fraction is known)

  • Combined reaction mass (water+antiprotons): ~0.8kg/L in tankage. Tank mass is 5.1% the reaction mass. (95.1% reaction mass)
  • Gross mass/dry loaded mass: 1.9731        = 835.4 t
  • Tankage mass/dry loaded mass: 0.0496  = 21 t
  • Engine mass/dry loaded mass: 0.6906     = 292.4 t
  • Payload mass/dry loaded mass: 0.2362.  = 100 t
  • Misc structural mass: 0.0236                      = 10 t
  • Dry empty mass:                                            = 323.4 t
  • Water propellant mass                                  = 412 t
  • Antiproton fuel mass                                     = ~0.41 kg
    • Total vacuum (sea level) thrust: 17.21 (11.47) MN
    • Total height: 43.3 meters
  • dV (no payload): 19340 m/s
  • (no payload) Vacuum (Sea level) TWR: 2.39 (1.59)
    • Time to fill by US fire hydrant (500-1500 gal/min): 1.2 to 3.6 hours
    • Time to fill by average garden hose (17 gal/min): 4.44 days

For comparison, Starship (just the upper stage) has a 9 meter diameter, is 50 meters tall, and weighs ~1420 tons fully fueled with payload.

 

So you are saying that this ship is smaller and,weighs less than Elon's starship and is better... only because of AM?

Wow.

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Yeah, antimatter is kind of insane, and thats with using less efficient water as a propellant. This craft could probably only get 100t payloads off of worlds less than 2 Earth masses with thin earthlike atmospheres, which should cover most "Earthlike" planets. On smaller worlds however, its payload capacity skyrockets. Quick table of parameters for the same vehicle for different world sizes. (limiting vehicle parameter in bold)

World Mars         Ganymede  Pluto        

Ceres        

Required dV (km/s) 4 2 1 0.3
Gravity (gee) 0.38 0.15 0.06 0.03
Low Orbit Payload (t) 1460 4800 8760 27100
TWR (local) 1.4 1.68 2.05 1.4
Vessel dV (km/s) 4.9 2 1 0.35

 

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4 hours ago, wafflemoder said:

Yeah, antimatter is kind of insane, and thats with using less efficient water as a propellant. This craft could probably only get 100t payloads off of worlds less than 2 Earth masses with thin earthlike atmospheres, which should cover most "Earthlike" planets. On smaller worlds however, its payload capacity skyrockets. Quick table of parameters for the same vehicle for different world sizes. (limiting vehicle parameter in bold)

World Mars         Ganymede  Pluto        

Ceres        

Required dV (km/s) 4 2 1 0.3
Gravity (gee) 0.38 0.15 0.06 0.03
Low Orbit Payload (t) 1460 4800 8760 27100
TWR (local) 1.4 1.68 2.05 1.4
Vessel dV (km/s) 4.9 2 1 0.35

 

Nice.

 

So a proper scifi SSTO then?

Takeoff to orbit, reentry and with enough propelllant left for landing?

What is really interesting is that this ship is like a jack of all trades exploration ship for Earth worlds.

But if flying to lower g worlds like Mars, the moon, or elsewhere you really can't refuel your water supply easily like on Earth.

Which logically means that spaceships FOR Earth worlds ONLY fly to Earth worlds, and Mars ships are designed only for mars etc. Simply because exoplanet resource refueling is the only choice a near empty rocket has. Sill easier than mining and processing metal ores offworld.

Want to trade cargo? Rendezvous in orbit with Earth ship and have it go back to Earth.

Edited by Spacescifi
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A ship like that would probably be able to refuel from water ice and hydrates. This would allow it refuel basically anywhere. The only locations in our solar system such a vessel wouldn't be able to refuel from would be Venus, Jupiter, Saturn, Uranus, Neptune, and possibly Io. Nearly all outer solar system bodies (with the exception of Io, and possibly some minor bodies) have thick crusts of icy material. Main belt objects like Ceres and Vesta have hydrate minerals at the surface, where water can be cooked out of them fairly easily. Mars has considerable amounts of ice under much of its surface, as well as hydrated minerals. Mercury and the Moon only have water ice in polar craters, and I don't believe they have any hydrated minerals.

The ship would still be limited by its antimatter reserves, but it could dedicate a fraction of its payload volume to more antimatter.

With the amount of antimatter present on this ship, (about a pound), the storage efficiency has a negligible impact on the overall craft specifications. Even so, the antimatter containment unit is 100 times more massive than the antimatter itself, while this is slightly optimistic for magnetic storage, it isn't something unattainable with the efficiencies of storing more than a few thousand atoms at a time. You could alternatively have antihelium stored inside fullerenes, for a tankage fraction of ~200:1, which is in the same ballpark as what is being used. Magnetic levitation of antihydrogen ices might be able to approach tankage fractions of 1:1 or lower, but I decided against using it from the potential danger of a single centralized antimatter container.

Edited by wafflemoder
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7 hours ago, wafflemoder said:

A ship like that would probably be able to refuel from water ice and hydrates. This would allow it refuel basically anywhere. The only locations in our solar system such a vessel wouldn't be able to refuel from would be Venus, Jupiter, Saturn, Uranus, Neptune, and possibly Io. Nearly all outer solar system bodies (with the exception of Io, and possibly some minor bodies) have thick crusts of icy material. Main belt objects like Ceres and Vesta have hydrate minerals at the surface, where water can be cooked out of them fairly easily. Mars has considerable amounts of ice under much of its surface, as well as hydrated minerals. Mercury and the Moon only have water ice in polar craters, and I don't believe they have any hydrated minerals.

The ship would still be limited by its antimatter reserves, but it could dedicate a fraction of its payload volume to more antimatter.

With the amount of antimatter present on this ship, (about a pound), the storage efficiency has a negligible impact on the overall craft specifications. Even so, the antimatter containment unit is 100 times more massive than the antimatter itself, while this is slightly optimistic for magnetic storage, it isn't something unattainable with the efficiencies of storing more than a few thousand atoms at a time. You could alternatively have antihelium stored inside fullerenes, for a tankage fraction of ~200:1, which is in the same ballpark as what is being used. Magnetic levitation of antihydrogen ices might be able to approach tankage fractions of 1:1 or lower, but I decided against using it from the potential danger of a single centralized antimatter container.

 

Interesting.... that is quite good, but the irony is my scifi hyperdrive won't drop any spaceships off near any mass without a surface gravity of 1g or greater. 

And by near, I mean dropping out of hyperspace into low planetary orbit of a given celestial body.

All the planets in our solar system with the exception of Saturn and Jupiter have less than 1g gravity.

What does that mean?

It means we could drop off near Saturn or Jupiter with ease, or even drop off near the sun (suicidal by the way), but to go anywhere else we would have to burn propellant.

Which means I would need entirely different ships for intetplanetary orbit to orbit trips as proposed to the launch ships we have discussed at length.

I know the options for that... and even with AM the performance is not that great.... unless wait time is not a problem.

Of course an AM pusher plate changes that but I digress.

I guess it's not bad if I really want to write hard scifi. I suppose they could find a moon around Saturn or Jupiter and refuel a water AM thermal rocket in good time.

Edited by Spacescifi
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