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Spacescifi

The Case For Solid Rocketry To Space

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Posted (edited)

 

If antimatter ever becomes more efficiently produced, would not dirt as propellant be sufficient to reach the Karman line and then use chemical rockets for orbital insertion?

The catch is that we are igniting the dirt with a liberal amount of antimatter.

 

The whole reason for this idea is cheap and easy refueling. Just land, take out the tractor. Scoop. Dump.

Liftoff!

Of course it's going to be bunch of ashy black exhaust but that's the price we pay.

 

Liquid propellant is best used for spqce anyway where efficiency matters most.

What do you think?

Take the size and mass of starshipX (Elon's) as a rough estimate to calculate from.

Could dirt and antimatter be enough to loft it into space? Not orbit, as the chemical AM thermal enginea do that.

 

On the moon it seems VERY viable.

 

Earth I can only hope so.

Edited by Spacescifi

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I'd advise you to stop mixing tech levels. That doesn't make for a good story. To make a believable SF you need to think about how a given technology impacts all areas of life. If you have an antimatter rocket, you can probably design your ship not to need to take up propellant at all, for an extended period of time.

Besides, if you have antimatter, why need dirt? You can use the air around you, unless you're on an airless body, in which case dirt makes sense. More to the point, why use chemical propulsion at all, outside of an emergency backup system? 

Also, it's propellant, not fuel. Your fuel is antimatter (admittedly, there's some propellant annihilated, but an insignificant amount). Your propellant is air, dirt and/or antimatter reaction products.

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40 minutes ago, Dragon01 said:

I'd advise you to stop mixing tech levels. That doesn't make for a good story. To make a believable SF you need to think about how a given technology impacts all areas of life. If you have an antimatter rocket, you can probably design your ship not to need to take up propellant at all, for an extended period of time.

Besides, if you have antimatter, why need dirt? You can use the air around you, unless you're on an airless body, in which case dirt makes sense. More to the point, why use chemical propulsion at all, outside of an emergency backup system? 

Also, it's propellant, not fuel. Your fuel is antimatter (admittedly, there's some propellant annihilated, but an insignificant amount). Your propellant is air, dirt and/or antimatter reaction products.

 

You suppose I have not already thought of the other implicatiions?

Easy antimatter production also means efficient storage and failsafes otherwise crews would never use it.

Dirt propellant is the difference between using just air and AM, which may not provide enough thrust.

 

Mixing tech levels?

If I wanted to make explorer spaceships that can land,, refuel, and relaunch, this is the quickest solution I can think up.

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Air will suffice if you heat it up enough. For an explorer spaceship, it is probably better to carry enough onboard propellant to come down and back up without needing to refuel planetside. Methane and water are good candidates. The former is more efficient, the latter has many other uses. The problem with solids is that they're very diverse. You don't know what you'll find, you don't want to be stuck on a surface that is made out of something that causes your tractor to melt. With gasses, it's easier to see what you're flying into ahead of time, but the surface will not always be visible. Air will provide enough thrust on any planet that has a surface (since H2 and He atmospheres pretty much only happen on gas giants).

My advice is: run the numbers. It's the best way of making sure your design checks out. Chemical propulsion, in particular, is not very useful if you have antimatter.

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33 minutes ago, Dragon01 said:

Air will suffice if you heat it up enough. For an explorer spaceship, it is probably better to carry enough onboard propellant to come down and back up without needing to refuel planetside. Methane and water are good candidates. The former is more efficient, the latter has many other uses. The problem with solids is that they're very diverse. You don't know what you'll find, you don't want to be stuck on a surface that is made out of something that causes your tractor to melt. With gasses, it's easier to see what you're flying into ahead of time, but the surface will not always be visible. Air will provide enough thrust on any planet that has a surface (since H2 and He atmospheres pretty much only happen on gas giants).

My advice is: run the numbers. It's the best way of making sure your design checks out. Chemical propulsion, in particular, is not very useful if you have antimatter.

 

Heating up the air enough is an issue, a non trivial issue.

In theory you could launch Elon's StarshipX with an antimatter thermal air rocket.... assuming we did not melt the engine trying.

More heat/energy required to provide the momentum transfer for stuff that weighs less (air).

Dirt would require less AM thermal energy for thrust, since the mass flow will be higher.

 

As for diverse solid propellant,I do not see at as a problem because there are solutions.

Send a probe down first to sample the soil.

Good?

Okay, land the whole ship and use chemical engines to slow for landing.

Then refuel dirt propellant and chemical if possible.

Launch again.

Chemical propellant can be pulse or constant. Whereas solid propellant burns constant till it runs out.

Thus the use of chemical propellant for landings.

It is a good idea to have at least two engines on an explorer.

One for powerful for launch, and another for orbital maneuvering.

In my example, chemical engines do double duty as orbital and landing engines.

As for numbers.... not my strong suite.

 

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If heat the steam boiler in a railroad locomotive with antimatter, we'll get a cheap and easy replacement for coal.

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Posted (edited)

Nuclear reactors use steam turbines or Stirling engines. Fusion or antimatter would use them, too, heating up water is a reasonably efficient way of capturing the energy. Yes, if you want to power a train with anything other than combustion or electricity, it will be a steam train. 

[Snip]

Edited by James Kerman
redacted by a moderator

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Some content has been removed. Personal attacks never advance the discussion so lets avoid them, please.

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12 hours ago, Spacescifi said:

If antimatter ever becomes more efficiently produced, would not dirt as propellant be sufficient to reach the Karman line and then use chemical rockets for orbital insertion?

WHY

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16 hours ago, Spacescifi said:

The whole reason for this idea is cheap and easy refueling. Just land, take out the tractor. Scoop. Dump.

Scooping dirt isn’t always easy! How many tons of propellant would you need? 
What if you land on rock?

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Posted (edited)

Or on a glass spot appeared in the previous landing.

Edited by kerbiloid

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Posted (edited)

In general, matter-antimatter annihilation releases its energy as gamma rays and short-lived charged particles. And by short, I mean nanoseconds. You can use those charged particles to produce thrust (this is the idea behind the beam core rocket) but not very much. A beam core rocket has ridiculously high ISP and almost as ridiculously low thrust to weight, so its no good as a lifter engine.

Whether your antimatter-dirt rocket works will depend almost entirely on how well that dirt absorbs gamma rays and how efficiently the so-heated dirt (or decomposition products thereof) can be ejected through a nozzle to produce thrust. As  @Dragon01 pointed out, 'dirt' is pretty diverse stuff, so there are simply too many variables here to give you a proper answer.

However, consider gunpowder as an analogous case. Loosely scattered grains of gunpowder will burn but not do much else. Carefully compressed gunpowder will burn rapidly and evenly, and can be used as solid propellant in firework rockets. Somewhere in between those two extremes it will just explode.

Now consider dirt as a heterogenous mass of stuff, the various components of which probably don't absorb gamma rays to the same extent (if at all) and so probably won't heat up particularly evenly. That, to me, sounds like a recipe for horribly random combustion instability and, most likely a short-lived, engine-rich exhaust.

TL:DR, I predict that shovelling dirt into your propellant tank and adding antimatter will lead to either not much happening or Bad Things happening.

Edited by KSK

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Posted (edited)

Which isotopes will appear if oxygen-16 annihilates with anti-lithium-7? If iron-56 does? If aluminium with anti-iron?

Edited by kerbiloid

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Posted (edited)
1 hour ago, KSK said:

In general, matter-antimatter annihilation releases its energy as gamma rays and short-lived charged particles. And by short, I mean nanoseconds. You can use those charged particles to produce thrust (this is the idea behind the beam core rocket) but not very much. A beam core rocket has ridiculously high ISP and almost as ridiculously low thrust to weight, so its no good as a lifter engine.

Whether your antimatter-dirt rocket works will depend almost entirely on how well that dirt absorbs gamma rays and how efficiently the so-heated dirt (or decomposition products thereof) can be ejected through a nozzle to produce thrust. As  @Dragon01 pointed out, 'dirt' is pretty diverse stuff, so there are simply too many variables here to give you a proper answer.

However, consider gunpowder as an analogous case. Loosely scattered grains of gunpowder will burn but not do much else. Carefully compressed gunpowder will burn rapidly and evenly, and can be used as solid propellant in firework rockets. Somewhere in between those two extremes it will just explode.

Now consider dirt as a heterogenous mass of stuff, the various components of which probably don't absorb gamma rays to the same extent (if at all) and so probably won't heat up particularly evenly. That, to me, sounds like a recipe for horribly random combustion instability and, most likely a short-lived, engine-rich exhaust.

TL:DR, I predict that shovelling dirt into your propellant tank and adding antimatter will lead to either not much happening or Bad Things happening.

 

Good points, so I would have to compress the dirt before shoving it in the propellant tank.

So drop it in the compressor filled.

Problem solved?

 

I wish lol.

Well. Did not know rocketry was so hard.

Copious amounts of stored antimatter still requires a fuel processor of propellant if you ever want good thrust once initial fuel runs out.

Other solution:  Use an antimatter powered laser to burn the dirt out the nozzle to provide thrust.

Has waste heat issues but the idea is workable in principle. Could use dirt as a heat sink and shoot it out the nozzle.

 

Edited by Spacescifi

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1 hour ago, Spacescifi said:

Copious amounts of stored antimatter still requires a fuel processor of propellant if you ever want good thrust once initial fuel runs out.

Other solution:  Use an antimatter powered laser to burn the dirt out the nozzle to provide thrust.

Has waste heat issues but the idea is workable in principle. Could use dirt as a heat sink and shoot it out the nozzle.

You really need to define what this 'dirt' is made of.

Moon dirt(lots of silica and Al) is very different from mars dirt(basalt, so mostly calcium and iron) which is very different from earth dirt(lots of carbon and silica) which is is very different from Pluto 'dirt'(mostly frozen gases).

The grain size, grain shape and most importantly gamma ray absorption will all vary wildly from each other. 

Using unrefined dirt for a rocket propellant is sort of like trying to fuel a steam engine using unspecified 'fuel'(could be nitroglycerine one day, and damp wood the next day, followed by gun cotton the third day and black powder on the fourth day, liquid hydrogen on the fifth day and liquid methane on the sixth day, then coal on the seventh day, and you don't know what it is or what it will be, as everything comes in 10kg boxes that you just toss into the burner).   

 

 

The value of using water/ice is that it is very easy to refine(melt it and let the gasses escape while letting solids settle), the value of air is that it is easy to collect(when present).

The value of using unrefined 'dirt' is the betting pool on how the rocket will explode when the 'propellant' is heated.

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4 hours ago, Terwin said:

You really need to define what this 'dirt' is made of.

Moon dirt(lots of silica and Al) is very different from mars dirt(basalt, so mostly calcium and iron) which is very different from earth dirt(lots of carbon and silica) which is is very different from Pluto 'dirt'(mostly frozen gases).

The grain size, grain shape and most importantly gamma ray absorption will all vary wildly from each other. 

Using unrefined dirt for a rocket propellant is sort of like trying to fuel a steam engine using unspecified 'fuel'(could be nitroglycerine one day, and damp wood the next day, followed by gun cotton the third day and black powder on the fourth day, liquid hydrogen on the fifth day and liquid methane on the sixth day, then coal on the seventh day, and you don't know what it is or what it will be, as everything comes in 10kg boxes that you just toss into the burner).   

 

 

The value of using water/ice is that it is very easy to refine(melt it and let the gasses escape while letting solids settle), the value of air is that it is easy to collect(when present).

The value of using unrefined 'dirt' is the betting pool on how the rocket will explode when the 'propellant' is heated.

 

I would argue that the main value of using dirt, whatever it's composition, is that it is far more plentiful than anything else.

 

Ice is great, but it is not as common as dirt is in space. Not every planet even has H2O ice, although they may have CO2 ice.

The advantage of dirty drives is that you can literally refuel anywhere.

 

I guess the biggest change is that ships would have to refine the dirt into it's liquid components and use that as as propellant.

Or refine the dirt into a powder for the solid rocket, which would be probably harder than just extracting chemicals from it for propellant.

 

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The "dirt" exists only on the Earth.
Others have rock, sand, and ice of various composition.

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“Dirt” doesn’t exist any more than “fish” do- there are big fish, small fish, fish that can fly, fish that can breathe air, fish that aren’t fish at all (crustaceans for one) but show most people pictures of them and they will identify them as “fish” regardless of the myriad differences between, say, a goldfish and a thresher shark.

Likewise, any random solid planetary body will contain a variety of minerals and compounds of varying composition, but collectively it’s easier to just call it “dirt” even though what’s in it varies widely.

 

If you’re going to fuel your interstellar rocket on any random solids, why bother landing at all? Solar systems are full of rocks floating around in asteroid belts, planetary rings and zones like the Kuiper belt and Oort Cloud, which are easily grabbed and could be collected by smaller autonomous drones and carried back to the mothership without having to land at all.

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Posted (edited)

Presumably, landing is the whole point. This is for an exploration ship, after all, which lands on planets to do its thing. The idea is that since you burn propellant on your way down, you want to top up before you go up. That said, I'm not convinced solids are the way to do it. Things like sand, in particular, have a high melting point and even if you run your engine hot enough to turn them into gas, they'll solidify and settle on the closest surface they can find as soon as they cool down. That's hard to deal with.

Edited by Dragon01

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Posted (edited)
2 hours ago, Dragon01 said:

Presumably, landing is the whole point. This is for an exploration ship, after all, which lands on planets to do its thing. The idea is that since you burn propellant on your way down, you want to top up before you go up. That said, I'm not convinced solids are the way to do it. Things like sand, in particular, have a high melting point and even if you run your engine hot enough to turn them into gas, they'll solidify and settle on the closest surface they can find as soon as they cool down. That's hard to deal with.

 

Right.

Assuming there is no water and you just want to mine metals, an airless low gravity moon or planet is a good choice. Yet refueling is the problem.

So if there is no easy way IRL, we could just deal with it.

If we have warp ability, we just carry enough propellant and resources for a single mission and return home at warp.

Which means every mission is a round trip home. To refuel and restock, even though they carry enough to do the landing and relaunch off the destination.

Because warp alone won't match velocity with landing spots, unless you warped repeatedly and dropped out for gravity assist, which still requires propellant for landing.

So unlike Star Trek, we outfit for one mission and warp back home. Outfit, do it again.

Can't just go hop from planet to planet since refueling is such an issue.

Edited by Spacescifi

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