Part Submarine... All Resuable Scifi SSTO

[Spacescifi]

 

This idea is borne from our current understanding of what physics allows for.

 

The SSTO: Imagine a submarine with a nuclear pusher plate at the rear... but with antimatter/matter bombs instead of nukes. It also has propeller engines for underwater propulsion on opposite sidewalls of the rear hull.

 

I have read somewhere that AM bombs actually leave less fallout than fission based bombs (all 'known' nuclear bombs have a fission bomb trigger). Even though their power is greater.

 

Max Payload: 40 tons cargo.

Max Crew: 40.

Launch scenario: The sub/SSTO leaves a coastal docking port until it is several kilometers from the coast (regulators will have work to do here).

Then it releases a bomb, waits for it to sink far down enough for safe detonation, and then the ship rises from the water, nose skyward and emerging partially from the ocean using propellers only. Then it detonates the bomb.

 

The thrust propels the pusher plate sub out of the water, and repeated detonations allow it to make orbit.

 

Landing: Landing by detonating AM bombs is suicide, but landing with belly rocket thrusters using nuclear or AM heated chemical propellant mixed with,an air breathing system most certainly is not.

Still... it's gonna land in the ocean.

Then propel itself like a sub to the nearest dock, unload, and repeat the entire process.

EDIT: Just one example of what we could do if we had working amounts antimatter and a reliable  abd safe compact way of storing it.

What you would not do... ever: Land on land. Unless you had to.

Since the landing is not the problem, as you have propellant alloted for that.

Relaunching is, since anything within a few kilometers will be obliterated.

The ocean don't care... well PETA might be upset for the fishies... but we will have to ignore their wealthfare to do this... at least whoever is in the blast radius. Since I do not see any company herding out the fishies before launch.

You may discuss.

 

Edited November 27, 2019 by Spacescifi

[Nightside]

Don’t be to hard on PETA, they’re just trying to protect us all from AM Godzillas 

[wumpus]

Why do you care about antimatter scaling?  With fission bombs you need at least critical mass, so mass efficiency scales up sharply after some minimum critical mass and eventually falls down as the bomb simply blows itself faster than it can split more nuclei.  Antimatter doesn't care about scaling: you throw "m" amount of antimatter in a non-vacuum chamber and you get 2mc² energy.  You might as well make a simple rocket (assuming that you can evenly stream antimatter out of your containment device.  But I can't imagine the containment device is remotely more difficult/complicated than accumulating the anti-matter.  There's no need for (low frequency) pulsed rocketry with antimatter.

If the blast emits radioactive fallout (like Orion) it makes a lot of sense to launch from Antarctica.  Then PETA is likely more concerned with the penguins.  But I doubt that Orion-like difficulties would happen with such a device.

Edited November 27, 2019 by wumpus
how did I mispell "throw"?

[Spacescifi]

18 minutes ago, wumpus said:

Why do you care about antimatter scaling?  With fission bombs you need at least critical mass, so mass efficiency scales up sharply after some minimum critical mass and eventually falls down as the bomb simply blows itself faster than it can split more nuclei.  Antimatter doesn't care about scaling: you through "m" amount of antimatter in a non-vacuum chamber and you get 2mc² energy.  You might as well make a simple rocket (assuming that you can evenly stream antimatter out of your containment device.  But I can't imagine the containment device is remotely more difficult/complicated than accumulating the anti-matter.  There's no need for (low frequency) pulsed rocketry with antimatter.

If the blast emits radioactive fallout (like Orion) it makes a lot of sense to launch from Antarctica.  Then PETA is likely more concerned with the penguins.  But I doubt that Orion-like difficulties would happen with such a device.

 

AM bombs beat nuclear bombs since you can scale down farther and still have high yields that equal or even surpass nukes.

Rocketry is limited by the thermal limits of the engine walls, which limits the amount of thrust you can achieve with an SSTO.

A pusher plate allows for even greater thrust since the reaction is not contained, but outside and pushing the ship away. Thus you do not worry about a melting engine.

Even the plate can be protected from ablation damage by spraying it with oil between bomv detonations.

 

AM bombs are an ideal form of orion pusher plate propulsion. Rockets have limits that pusher plates do not... so that is why I propose AM orion drive submarine SSTOs.

[magnemoe]

25 minutes ago, wumpus said:

Why do you care about antimatter scaling?  With fission bombs you need at least critical mass, so mass efficiency scales up sharply after some minimum critical mass and eventually falls down as the bomb simply blows itself faster than it can split more nuclei.  Antimatter doesn't care about scaling: you through "m" amount of antimatter in a non-vacuum chamber and you get 2mc² energy.  You might as well make a simple rocket (assuming that you can evenly stream antimatter out of your containment device.  But I can't imagine the containment device is remotely more difficult/complicated than accumulating the anti-matter.  There's no need for (low frequency) pulsed rocketry with antimatter.

If the blast emits radioactive fallout (like Orion) it makes a lot of sense to launch from Antarctica.  Then PETA is likely more concerned with the penguins.  But I doubt that Orion-like difficulties would happen with such a device.

Yes you don't need pulses, its probably simpler to simply have an stream of antimatter into the engine and you can use air as reaction mass if you want to however other materials might work better. 

However the main problem with antimatter outside of price is that if containment fails it all blow up. And having antimatter bombs makes this worse as if one blow up it will destroy the containment on other bombs giving you an chain reaction. 
With only one antimater container its just one containment and you can make it as good as possible. 
 

[Spacescifi]

14 minutes ago, magnemoe said:

Yes you don't need pulses, its probably simpler to simply have an stream of antimatter into the engine and you can use air as reaction mass if you want to however other materials might work better. 

However the main problem with antimatter outside of price is that if containment fails it all blow up. And having antimatter bombs makes this worse as if one blow up it will destroy the containment on other bombs giving you an chain reaction. 
With only one antimater container its just one containment and you can make it as good as possible. 
 

 

Good point.

So an antimatter project pluto air breathing rocketship could work in theory. 

 

It is still thermally limited, which means pound for pound,, you can ship more payload via orion style than you could with rocketry of any kind currently known.

Big advantages require greater risk. But I also assume the containment chambers are advanced enough to convert the AM back to normal matter... at least if I was making scifi.

Making antimatter would be just as easy.

[kerbiloid]

Spoiler

If heat a steam engine boiler with annihilating antimatter, we can make an antimatter-powered steampunk submarine.

 

[sevenperforce]

1 hour ago, Spacescifi said:

So an antimatter project pluto air breathing rocketship could work in theory. 

It is still thermally limited, which means pound for pound,, you can ship more payload via orion style than you could with rocketry of any kind currently known.

Incorrect. Antimatter is not thermally limited. If you have trouble with heat, you can use as much atmospheric cooling as you want. By the time you're out of the atmosphere, thrust is not as important, and so you again have no problems.

If you have good antimatter containment then just build SABRE but with antimatter.

 

[Spacescifi]

9 minutes ago, sevenperforce said:

Incorrect. Antimatter is not thermally limited. If you have trouble with heat, you can use as much atmospheric cooling as you want. By the time you're out of the atmosphere, thrust is not as important, and so you again have no problems.

If you have good antimatter containment then just build SABRE but with antimatter.

 

 

The engine is. And how much atmospheric cooling you get depends on other factors like:

 

How big are your intakes? How heavy is your vessel, as heavier vessels take longer to lift off, which means unless your vessel has a whole lot of intakes on it, it will have the least atmospheric cooling during the initial launch phase. As it speeds through the air it will get more cooling from oncoming air. But for the initial liftoff you should probably use propellant mixed with intake air.

There is a certain sweet spot for air intake speed cooling, especially when using antimatter. I

You need enough intake air otherwise your engine melts or you must inject cool liquid hydrogen.

Edited November 27, 2019 by Spacescifi

[sevenperforce]

2 minutes ago, Spacescifi said:

How big are your intakes? How heavy is your vessel, as heavier vessels take longer to lift off, which means unless your vessel has a whole lot of intakes on it, it will have the least atmospheric cooling during the initial launch phase. As it speeds through the air it will get more cooling from oncoming air. But for the initial liftoff you should probably use propellant mixed with intake air.

There is a certain sweet spot for air intake speed cooling, especially when using antimatter. I

You need enough intake air otherwise your engine melts or you must inject cool liquid hydrogen.

Then inject cool liquid hydrogen. You have a five-digit specific impulse in vacuum; you can carry anything you want. In the atmosphere you probably have a seven-digit specific impulse. This is a torchship.

[Spacescifi]

8 minutes ago, sevenperforce said:

Then inject cool liquid hydrogen. You have a five-digit specific impulse in vacuum; you can carry anything you want. In the atmosphere you probably have a seven-digit specific impulse. This is a torchship.

 

I thought specific impulse was how long propellant lasted? Or is it a measure of how much thrust you can get out of your propellant?

[sevenperforce]

47 minutes ago, Spacescifi said:

I thought specific impulse was how long propellant lasted? Or is it a measure of how much thrust you can get out of your propellant?

Specific impulse is the amount of thrust you get out of each kilogram of propellant. Propellant mass being equal, a rocket with 100kN of thrust and a specific impulse of 450 seconds will burn for longer (and therefore deliver greater total impulse) than a rocket with 100kN of thrust and a specific impulse of 320 seconds.

With the five-digit specific impulse of an antimatter rocket, you can pretty much burn continuously for as long as you want because you are using so little antimatter each second.

[wumpus]

1 hour ago, sevenperforce said:

Then inject cool liquid hydrogen. You have a five-digit specific impulse in vacuum; you can carry anything you want. In the atmosphere you probably have a seven-digit specific impulse. This is a torchship.

More like (low) 4 digit Isp for orbital insertion while in vacuum, assuming you are just heating up liquid hydrogen and spitting it out like a nuclear thermal rocket.  You won't need to cool a reactor, but you still need to keep the throat/nozzle from melting and that keeps the exhaust temperature not much higher than the SSMEs (which was mostly water, so it had a much lower Ve).  If you don't need that type of thrust (you aren't in danger of falling back into a gravity well), you can probably easily hit 5 digit Isp (just don't expect to get 1g burns to generate that nice artificial gravity).

But yeah.  Torchship.

3 hours ago, Spacescifi said:

 

AM bombs beat nuclear bombs since you can scale down farther and still have high yields that equal or even surpass nukes.

Rocketry is limited by the thermal limits of the engine walls, which limits the amount of thrust you can achieve with an SSTO.

A pusher plate allows for even greater thrust since the reaction is not contained, but outside and pushing the ship away. Thus you do not worry about a melting engine.

Even the plate can be protected from ablation damage by spraying it with oil between bomv detonations.

 

AM bombs are an ideal form of orion pusher plate propulsion. Rockets have limits that pusher plates do not... so that is why I propose AM orion drive submarine SSTOs.

If you are using arbitrarily small antimatter explosions, why bother with heated chemicals?  While you might have a pusher plate you still want to have the thing run in thousands of bombs per second (possibly higher.  But even then I doubt you could hide the noise).  But launching/landing would still almost certainly use antimatter SCRAMJETS.

I'd assume that an Orion would never attempt to land, and that antimatter SCRAMJETS would be used on shuttles to/from the Orion.  Hoverslamming a SCRAMJET is an exersize for the reader, so I suspect that such craft would include Shuttle-like wings (I hate the shuttle's wings, but antimatter fixes virtually all rocket issues).

Edited November 27, 2019 by wumpus

[sevenperforce]

4 minutes ago, wumpus said:

More like (low) 4 digit Isp for orbital insertion while in vacuum, assuming you are just heating up liquid hydrogen and spitting it out like a nuclear thermal rocket.  You won't need to cool a reactor, but you still need to keep the throat/nozzle from melting and that keeps the exhaust temperature not much higher than the SSMEs.

High 4-digit at worst. You can use regenerative cooling to keep the throat and nozzle solid. Hell, with antimatter-level energy density, you can afford to use film cooling and still hit high four-digit Isp.

4 minutes ago, wumpus said:

If you don't need that type of thrust (you aren't in danger of falling back into a gravity well), you can probably easily hit 5 digit Isp (just don't expect to get 1g burns to generate that nice artificial gravity).

That's where radiators come into play.

[KSK]

We're also assuming a device that is capable of easy conversion of antimatter to matter and back again. At which point, as a reader, I really don't care about melting engines, ISP or whatever. In fact, the shift from focusing on technical plausibility and hard sci-fi, to throwing in this huge McGuffin piece of technology is quite likely to break whatever immersion I had in your story. 

By all means have your matter-antimatter converter. Your story, your rules. But at that point you may as well just use your spacecraft as a backdrop for the story and just assume it can do whatever you need it to do without bogging the story down with more or less spurious technical justifications for stuff. 

Edited November 27, 2019 by KSK

[sevenperforce]

1 minute ago, KSK said:

We're also assuming a device that is capable of easy conversion of antimatter to matter and back again. At which point, as a reader, I really don't care about melting engines, ISP or whatever. In fact, the shift from focusing on technical plausibility and hard sci-fi, to throwing in this huge McGuffin piece of technology is quite likely to break whatever immersion I had in your story. 

By all means have your matter-antimatter converter. But at that point you may as well just use your spacecraft as a backdrop for the story and just assume it can do whatever you need it to do without bogging the story down with more or less spurious technical justifications for stuff. 

Yeah, the Convert-O-Tron element is pure hokey. That pretty nearly violates conservation of energy. Antimatter is an energy storage mechanism, not an energy generation mechanism.

[wumpus]

11 minutes ago, sevenperforce said:

High 4-digit at worst. You can use regenerative cooling to keep the throat and nozzle solid. Hell, with antimatter-level energy density, you can afford to use film cooling and still hit high four-digit Isp.

That's where radiators come into play.

Last I heard (some astronaut trying to explain rocket science to non-nerds), SSME was pretty much at the melting point already and regeneratively cooled with the LOH.  And of course radiators aren't going to work in orbit.

But the bigger question is why you couldn't just accelerate to orbital velocity within the atmosphere.  Normal SCRAMJETs are next to impossible at that speed, but the only issue antimatter has is where the stuff will first hit matter.

Edit: please don't make a Convert-o-tron that produces energy.  It really needs to require (at least) 2mc² energy per "m" of antimatter produced.  Violating the conservation of energy makes Harry Potter look like hard sci-fi.

Edited November 27, 2019 by wumpus

[kerbiloid]

Spoiler

The Matter Sign Switcher.
Anti <=> Not-Anti.

 

 

[Spacescifi]

31 minutes ago, wumpus said:

Last I heard (some astronaut trying to explain rocket science to non-nerds), SSME was pretty much at the melting point already and regeneratively cooled with the LOH.  And of course radiators aren't going to work in orbit.

But the bigger question is why you couldn't just accelerate to orbital velocity within the atmosphere.  Normal SCRAMJETs are next to impossible at that speed, but the only issue antimatter has is where the stuff will first hit matter.

Edit: please don't make a Convert-o-tron that produces energy.  It really needs to require (at least) 2mc² energy per "m" of antimatter produced.  Violating the conservation of energy makes Harry Potter look like hard sci-fi.

 

Setting has hyperdrives too... so go figure. Everything is justified by plot needs.

But if anyone wishes to utilize SSTO's as common place in scifi it requires stuff we do not have.

It is not safe otherwise and thus it's use cannot be justified as common enough to trade with across the starry heavens.

Because with only known abilities what have ya got? Project Orion SSTO variants with all the fallout issues, and ludicrously expensive antimatter vessels that would make Kanye and Elon both go bankrupt.

Edited November 27, 2019 by Spacescifi

[kerbiloid]

What amuses me a lot is why anybody thinks that antimatter is cleaner than traditional nukes.

It does not produce pure photons, how many times was it spoken.
It produces mostly 3.14-mesons of various signs which later decay into those photons.
But primarily these mesons will bombard everything next to the explosion zone causing various nuclear reactions and producing a hardly predictable mess of radioactive shisotopes.
As well such dense flow of gamma will cause additional nuclear reactions.
Also lightweight atoms will be accelerated and bombard matter beyond the reactions zone.
And if the yield is enough high and the temperature reaches fusion values this will make the fun grow moar.

***

And no, Orion/pusher plate is not an atmospheric engine. And not an underwater one. It probably can survive an atmospheric launch, but it does not use shockwaves for propulsion, it needs them as much as a car engine needs detonation (see "octane number", etc).
It is propelled with gaseous tungsten flow. The atmosphere doesn't help it, it drags the tungsten jet and dissipates its energy. In exchange it produces shockwaves killing the engine.

Also is doesn't have anything to do with antimatter, except causing fusion in a pellet, where the annihilation input is still negligible.
Because it doesn't need to be bombarded with 0.5 c fast tungsten cores, it works at ~150 km/s tungsten speed and is happy with this range of value, obviously achievable with any regular nuke.

[KSK]

1 hour ago, Spacescifi said:

Setting has hyperdrives too... so go figure. Everything is justified by plot needs.

But if anyone wishes to utilize SSTO's as common place in scifi it requires stuff we do not have.

It is not safe otherwise and thus it's use cannot be justified as common enough to trade with across the starry heavens.

Because with only known abilities what have ya got? Project Orion SSTO variants with all the fallout issues, and ludicrously expensive antimatter vessels that would make Kanye and Elon both go bankrupt.

Yeah, that's kind of my point. You're writing a setting where access to space is so safe and commonplace that interstellar trade is a thing. You're positing a technology level where creation, storage and control of antimatter is easy and reliable.

But then you throw in a load of detail which gives the exact opposite impression. The weight of your spacecraft is a factor. Engine running temperature is a factor. Propellant quantity is a factor. These are all things that suggest that spaceflight is still hard and risky and, speaking as a reader, it jars.

Put another way, if I was writing a story set in the present day, I might have one of my characters cross the Atlantic in an airliner. Unless anything of note happened along the way, there wouldn't be much to say about it. My character buys a ticket, goes to the airport, maybe lets it all hang out a bit over some piece of (as he sees it) security pantomime, gets on his plane and falls asleep. The next paragraph he's debarking, checking his coat pocket for his passport and resigning himself to more security checks.

The design and technical details of the airliner wouldn't get a moment of page time. They're normal, they're routine, my character in all probability doesn't know much about them and if he did he wouldn't care enough for them to warrant a mention. He certainly wouldn't spend his flight wondering about the make, model and ISP of whatever turbofan was pushing him through the sky, still less fret about the operating temperature of the turbine at the core of that turbofan.

[KSK]

But moving on, if what you want is easy and reliable SSTO travel, why not go for an antimatter powered Skylon?

Skylon was designed to put 15 tons of payload into LEO. To do that it carried 250 tons of propellant. I don’t have numbers for how much of that was LOX and how much was hydrogen but from a simple consideration of molecular masses, most of those 250 tons would be LOX.

With an antimatter powered Skylon, LOX is dead weight because you don’t need to burn your fuel with an oxidiser. That frees up a vast amount of mass for extra payload and/or propellant. More than enough for an extra 25 tons of cargo and 40 crew.

Probably enough for multiple round trips to orbit and back especially if you assume a gliding reentry and a little bit of powered flight to your landing site. 

Or, as the saying goes - once you’re in LEO you’re halfway to anywhere - and with an antimatter Skylon you probably have the propellant reserve to get there.

If you want to make your sci-fi Skylon a bit more flexible, add belly thrusters and retrothrusters for landing away from pre-prepared runways.

And yeah Skylon is only a paper design thus far but on paper it works. Real life engineering considerations may well have eaten into that payload capacity to the point where the economics no longer worked but hey - that’s the beauty of fiction - you can assume that the paper design could become a reality.

And all of the above is assuming that the antimatter rocket powering your sci-fi Skylon is about as efficient and powerful (or has the same ISP and thrust) as a hydrolox engine which is likely to be an excessively conservative assumption.

Edited November 27, 2019 by KSK

[wumpus]

1 hour ago, KSK said:

But moving on, if what you want is easy and reliable SSTO travel, why not go for an antimatter powered Skylon?

The heart of Skylon is a system to cool incoming air (indirectly with LOH later used as fuel).  With anti-matter, such cooling really isn't necessary (although it would certainly help efficiency).  I'd recommend going straight to a SCRAMJET, although getting the thing started becomes an issue (which SABRE avoids by using compressors).

But the real point of "if you have temperature limits you almost certainly have fuel limits", and the problems you are asking about simply don't exist in a world with easily available antimatter and interstellar travel.  They are "technologies that no longer need improvement", quite possibly from centuries back (and whatever improvements they have is next to inconceivable as they are optimizing for things we can only guess about).

If you want to show off your knowledge of thermal limits, interstellar space isn't the place for it.  You'd need something set roughly in the 21st century.  Although I'm pretty sure trying to use less than .1m² of radiator per MW of power will require unobtanium (with near perfect themal conductivity, radiation, and a melting point over 4000K).

[Spacescifi]

5 minutes ago, wumpus said:

The heart of Skylon is a system to cool incoming air (indirectly with LOH later used as fuel).  With anti-matter, such cooling really isn't necessary (although it would certainly help efficiency).  I'd recommend going straight to a SCRAMJET, although getting the thing started becomes an issue (which SABRE avoids by using compressors).

But the real point of "if you have temperature limits you almost certainly have fuel limits", and the problems you are asking about simply don't exist in a world with easily available antimatter and interstellar travel.  They are "technologies that no longer need improvement", quite possibly from centuries back (and whatever improvements they have is next to inconceivable as they are optimizing for things we can only guess about).

If you want to show off your knowledge of thermal limits, interstellar space isn't the place for it.  You'd need something set roughly in the 21st century.  Although I'm pretty sure trying to use less than .1m² of radiator per MW of power will require unobtanium (with near perfect themal conductivity, radiation, and a melting point over 4000K).

 

You make a valid point. With stuff like FTL hyperdrives being cheap enough for interplanetary trade in mere days, they probably are more challenged by massive planetary modifications and add ons.

I would hardly be surprised if they had some type of vacuum reaction engine and stuck it on the backs of asteroids and small moons for thrust.

 

Still... the real reason I consider this is basically how to find a way to beat gravity and get massive payloads up without cheating make believe.

In space I don't mind making up stuff, as it is required to go anywhere interesting in a reasonable amount of time.

But lifting off a planet like Earth can be done several ways, one way among them being an MHD... which strangely enough, if powered via antimatter and it rocket engines too,  it could do a air rocket/air MHD combo to orbit.

 

So any somewhat more grounded approach to the challenges of SSTO flight is a composite solution... which in any case will require burning less propellant since the MHD is helping with fligh in tandem with the rockets.

 

 

 

[KSK]

5 hours ago, wumpus said:

The heart of Skylon is a system to cool incoming air (indirectly with LOH later used as fuel).  With anti-matter, such cooling really isn't necessary (although it would certainly help efficiency).  I'd recommend going straight to a SCRAMJET, although getting the thing started becomes an issue (which SABRE avoids by using compressors).

Very true. 'Antimatter powered Skylon' is a bit of a misnomer but Skylon was a convenient place to start, it being a present day airbreathing SSTO design that I could find some numbers for. 

5 hours ago, Spacescifi said:

Still... the real reason I consider this is basically how to find a way to beat gravity and get massive payloads up without cheating make believe.

 

15 hours ago, Spacescifi said:

But I also assume the containment chambers are advanced enough to convert the AM back to normal matter... at least if I was making scifi.

Making antimatter would be just as easy.

One of those things is not like the other.