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Revisiting WEAV but With Magnetic Nozzles and regenerative cooling


Spacescifi
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It has been said that Wingless Electromagnetic Air Vehicles (WEAV) main obstacle is power.

So lets assume we have enough electric power onboard an SSTO that is a WEAV to get it to orbit.

Lets also assume we use air plasma, magnetic nozzles and regenerative cooling on the magnetic nozzes as wel as stored fuel for plasma propulsion in space.

Could such a setup work provided a vessel has sufficient electriv power?

In space the magnetic nozzle would be needed with plasma exhaust.

 

I am also thinking that with regnerative cooling, you could use magnetuc nozzles like normal rocket nozzles to reach space before switching to plasma exhaust produced from onboard propellanr.

 

I presume such has never been done, but it sounds like a way to make a proper STTO if they have the power.

 

 

 

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1 minute ago, Spacescifi said:

It has been said that Wingless Electromagnetic Air Vehicles (WEAV) main obstacle is power

Provide references, please

2 minutes ago, Spacescifi said:

So lets assume we have enough electric power onboard an SSTO that is a WEAV to get it to orbit

Define how much power is needed.  That will dictate the size/weight of the vehicle

3 minutes ago, Spacescifi said:

Could such a setup work provided a vessel has sufficient electriv power?

Very hard to say without information.  You have the issue of shielding and electrical insulation, both electrical and magnetic.  Electricity is a funny thing, can work differently at extreme voltages

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2 hours ago, linuxgurugamer said:

Provide references, please

Define how much power is needed.  That will dictate the size/weight of the vehicle

Very hard to say without information.  You have the issue of shielding and electrical insulation, both electrical and magnetic.  Electricity is a funny thing, can work differently at extreme voltages

 

I see. Come to think of it... a more simple approach would be better.

Using electrodes with plasma to lift a vehicle into the air will run into the same problem as scramjets if they try to reach suborbital velocity. Air friction, which will likely erode the electrodes on each launch... making them single use. Regenerative cooling of electrodes may may not work, and if it does, only under certain degrees of heat from friction and no more than that.

 

A better solution than the original post: A scifi version of vasmir as an SSTO.

 

Normal bell nozzle, but an awesome source of power/electricity propels plasma out the nozzle at enough density and speed that it can launch navy destroyer weight-like (9,300 tons)  vessels as SSTO with only 10%  (930 tons) of the vessel's mass dedicated to propellant to ionize and exhaust as plasma.

Vessel would be capable of 1 hour of 3g to totally exhaust it's propellant, or 1g for 3 hours of 1g or something inbetween.

I do not know how much power/electricity is needed to acomplish this feat, but I reckon it is probably an absurd amount. Which is not exactly an obstacle for science fiction. Still, I think regenerative cooling could do wonders on any real VASMIR or wannabe torch drive

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8 hours ago, Spacescifi said:

Air friction, which will likely erode the electrodes on each launch... making them single use. Regenerative cooling of electrodes may may not work, and if it does, only under certain degrees of heat from friction and no more than that.

Do you know what "air friction" and "electrodes" and "regenerative cooling" are? Because it doesn't seem like you do.

8 hours ago, Spacescifi said:

A better solution than the original post: A scifi version of vasmir as an SSTO.

Normal bell nozzle, but an awesome source of power/electricity propels plasma out the nozzle at enough density and speed that it can launch navy destroyer weight-like (9,300 tons)  vessels as SSTO with only 10%  (930 tons) of the vessel's mass dedicated to propellant to ionize and exhaust as plasma.

Vessel would be capable of 1 hour of 3g to totally exhaust it's propellant, or 1g for 3 hours of 1g or something inbetween.

What you are describing has absolutely nothing in common with VASIMR (not "vasmir").

What you are describing is a torchship. 

First of all, the total weight of your proposed ship is ABSOLUTELY irrelevant. It doesn't matter. If you have a source of energy like the one you're describing, you could launch a spaceship that was 10 tonnes or 100 tonnes or 1,000 tonnes or 10,000 tonnes or 100,000 tonnes. Everything is scaleable. Saying "enough density and speed that it can launch navy destroyer weight" is meaningless, because it doesn't matter how big your payload is. If you want a bigger payload, cluster more engines. Everything scales.

In your first example, where your vehicle can reach LEO from Earth's surface in a single stage while expending only 10% of its mass as propellant, you will need an engine with a specific impulse of roughly 9,200 seconds and a T/W ratio that is large enough to get off the ground. Such an engine would have nothing in common with any engine that actually exists or has been proposed.

In your second example, where your vehicle is capable of going for 1 hour at 3 gees of acceleration or 3 hours at 1 gee of acceleration, it will have developed a whopping 105,498 m/s of dV. This is not a torchship; this is a blowtorchship. It is as different from your first example as an SR-71 is from a V-1 buzz bomb. Using the same mass ratios you described before, we would be looking at a specific impulse of approximately 105,100 seconds, or roughly 0.3% of the speed of light. You would need continuously evaporating Planck black holes wrapped in small, frangible moons to achieve that kind of thrust and impulse for even five minutes, let alone hours.

I feel like I've said this before, but let me say it again, @Spacescifi. If you want to have spaceships that do a thing, say that they do the thing. Don't try to make the science work because it won't. Call it warp drive or slipstream or temporal displacement or whatever else you want to call it, but don't try to make science do something it doesn't want to do.

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If we take the highest ISP ion thruster out there, the DS4G, and take its numbers (2,5 N of thrust for 250 kW of power), scale it to your destroyer sized spaceship, give it TWR of 1,5 to get off the ground, we get a continuous power requirement of around 14 TW, which happens to be about five times larger than total world electrical power generation.

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6 hours ago, Shpaget said:

If we take the highest ISP ion thruster out there, the DS4G, and take its numbers (2,5 N of thrust for 250 kW of power), scale it to your destroyer sized spaceship, give it TWR of 1,5 to get off the ground, we get a continuous power requirement of around 14 TW, which happens to be about five times larger than total world electrical power generation.

How much does it weigh, this thruster? I'm betting more than 2.5N.

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10 hours ago, sevenperforce said:

Do you know what "air friction" and "electrodes" and "regenerative cooling" are? Because it doesn't seem like you do.

What you are describing has absolutely nothing in common with VASIMR (not "vasmir").

What you are describing is a torchship. 

First of all, the total weight of your proposed ship is ABSOLUTELY irrelevant. It doesn't matter. If you have a source of energy like the one you're describing, you could launch a spaceship that was 10 tonnes or 100 tonnes or 1,000 tonnes or 10,000 tonnes or 100,000 tonnes. Everything is scaleable. Saying "enough density and speed that it can launch navy destroyer weight" is meaningless, because it doesn't matter how big your payload is. If you want a bigger payload, cluster more engines. Everything scales.

In your first example, where your vehicle can reach LEO from Earth's surface in a single stage while expending only 10% of its mass as propellant, you will need an engine with a specific impulse of roughly 9,200 seconds and a T/W ratio that is large enough to get off the ground. Such an engine would have nothing in common with any engine that actually exists or has been proposed.

In your second example, where your vehicle is capable of going for 1 hour at 3 gees of acceleration or 3 hours at 1 gee of acceleration, it will have developed a whopping 105,498 m/s of dV. This is not a torchship; this is a blowtorchship. It is as different from your first example as an SR-71 is from a V-1 buzz bomb. Using the same mass ratios you described before, we would be looking at a specific impulse of approximately 105,100 seconds, or roughly 0.3% of the speed of light. You would need continuously evaporating Planck black holes wrapped in small, frangible moons to achieve that kind of thrust and impulse for even five minutes, let alone hours.

I feel like I've said this before, but let me say it again, @Spacescifi. If you want to have spaceships that do a thing, say that they do the thing. Don't try to make the science work because it won't. Call it warp drive or slipstream or temporal displacement or whatever else you want to call it, but don't try to make science do something it doesn't want to do.

 

7 hours ago, Shpaget said:

If we take the highest ISP ion thruster out there, the DS4G, and take its numbers (2,5 N of thrust for 250 kW of power), scale it to your destroyer sized spaceship, give it TWR of 1,5 to get off the ground, we get a continuous power requirement of around 14 TW, which happens to be about five times larger than total world electrical power generation.

 

Thank you.

 

Sevenperforce, 10% of the destroyer weighted spaceship would be propellant either way. The energy source aboard would be potent enough to ionize and electromagnetically thrust out the plasma hard enough for the figures I gave.

 

They are not separate examples but one and the same. That 10% of propellant can last 3 hours at 1g, or 1 hour at 3g.

 

I too am curious how much the ion thruster would weigh... but that is not a good example since I am thinking of a plasma rocket like VASIMIR but on steroids as it were.

The main difference being a far more potent energy source to ionize and propel the plasma.

 

Question: I reckon such a vessel may just have to look like a classic belly lander SSTO.

Why? Use chemical dual axis thrusters for launch/landing, and flip to boost to orbit or slow your descent.

 

Why? Something tells me that shooting a plasma plume with 5 times the energy production of the entire planet at the ground may leave a crater or blow up the ground like a bomb.

 

SSTO's in scifi... this knowledge shows how powerful they would be if they had the same basic feats as depicted.

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1 hour ago, Spacescifi said:

Sevenperforce, 10% of the destroyer weighted spaceship would be propellant either way. The energy source aboard would be potent enough to ionize and electromagnetically thrust out the plasma hard enough for the figures I gave.

They are not separate examples but one and the same. That 10% of propellant can last 3 hours at 1g, or 1 hour at 3g.

Yes, thrusting for one hour at three gees or for three hours at one gee produce the same total impulse. I was not saying that those were different examples. I was saying that those two (equivalent) examples were completely different, separate, and dissimilar from your first example, where your spaceship burns 10% of its mass as propellant to reach LEO.

If you have a vehicle which can thrust for an hour at three gees, then it doesn't need to burn 10% of its mass as propellant to reach LEO. Reaching LEO would burn less than 1% of its mass.

1 hour ago, Spacescifi said:

Something tells me that shooting a plasma plume with 5 times the energy production of the entire planet at the ground may leave a crater or blow up the ground like a bomb.

Well, here you may be right.

An  Arleigh Burke-class navy destroyer has a minimum displacement of around 7000 tonnes.

In the example you've given, where the main engine delivers three gees of acceleration, you're looking at a thrust of 206 meganewtons. At a specific impulse of 105,100 seconds, the mass flow is approximately 200 kilograms per second. That might not seem like much, but if these 200 kilograms are accelerated to 0.3% the speed of light, that's a power rating of 1.06e11 kW. Not only is this the minimum power requirement of your engine (we'll get to that in a second), but more importantly it's the amount of energy in the engine plume. That is the equivalent of about 7 Hiroshima-sized nuclear bombs exploding every second. At this exhaust speed, the plasma plume doesn't even notice the atmosphere as it effortlessly excavates away the Earth's crust, leaving a time-zone-wide supervolcano at the launch site.

Let's talk about the engine energy requirements. VASMIR has a peak efficiency of about 73%, although conceivably a super-advanced model could reach a peak efficiency of around 87%. That should be approximately the physical limit. That means the engine will produce 1.6e10 kW of waste heat. With only 200 kilograms of propellant being expended per second, there's nowhere for that heat to go and no way to regeneratively cool the engine. Let's assume this navy destroyer spaceship has a surface area of around 8,300 square meters, just like the USS Cole. The spaceship will heat up until each square meter is radiating 1,927 kilowatts of heat. Assuming that the exterior surface is a perfect blackbody and ignoring the atmosphere, the average temperature of the spaceship will be 4,124 K or approximately 3850 degrees Celsius. That is significantly higher than the melting point of tungsten as well as the boiling point of steel.

And that engine? This "energy source" will need to come up with a way to produce 2.2e11 kW. Envisioning such an energy source will be left as an exercise for the reader. However, note that if pure fusion were used as the energy source, this would require the continuous fusion of approximately 350 kilograms of hydrogen per second. At least we don't have to worry about having enough propellant.

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56 minutes ago, sevenperforce said:

Yes, thrusting for one hour at three gees or for three hours at one gee produce the same total impulse. I was not saying that those were different examples. I was saying that those two (equivalent) examples were completely different, separate, and dissimilar from your first example, where your spaceship burns 10% of its mass as propellant to reach LEO.

If you have a vehicle which can thrust for an hour at three gees, then it doesn't need to burn 10% of its mass as propellant to reach LEO. Reaching LEO would burn less than 1% of its mass.

Well, here you may be right.

An  Arleigh Burke-class navy destroyer has a minimum displacement of around 7000 tonnes.

In the example you've given, where the main engine delivers three gees of acceleration, you're looking at a thrust of 206 meganewtons. At a specific impulse of 105,100 seconds, the mass flow is approximately 200 kilograms per second. That might not seem like much, but if these 200 kilograms are accelerated to 0.3% the speed of light, that's a power rating of 1.06e11 kW. Not only is this the minimum power requirement of your engine (we'll get to that in a second), but more importantly it's the amount of energy in the engine plume. That is the equivalent of about 7 Hiroshima-sized nuclear bombs exploding every second. At this exhaust speed, the plasma plume doesn't even notice the atmosphere as it effortlessly excavates away the Earth's crust, leaving a time-zone-wide supervolcano at the launch site.

Let's talk about the engine energy requirements. VASMIR has a peak efficiency of about 73%, although conceivably a super-advanced model could reach a peak efficiency of around 87%. That should be approximately the physical limit. That means the engine will produce 1.6e10 kW of waste heat. With only 200 kilograms of propellant being expended per second, there's nowhere for that heat to go and no way to regeneratively cool the engine. Let's assume this navy destroyer spaceship has a surface area of around 8,300 square meters, just like the USS Cole. The spaceship will heat up until each square meter is radiating 1,927 kilowatts of heat. Assuming that the exterior surface is a perfect blackbody and ignoring the atmosphere, the average temperature of the spaceship will be 4,124 K or approximately 3850 degrees Celsius. That is significantly higher than the melting point of tungsten as well as the boiling point of steel.

And that engine? This "energy source" will need to come up with a way to produce 2.2e11 kW. Envisioning such an energy source will be left as an exercise for the reader. However, note that if pure fusion were used as the energy source, this would require the continuous fusion of approximately 350 kilograms of hydrogen per second. At least we don't have to worry about having enough propellant.

 

Wow... so I guess a scifi torchship would need 99.99 efficiency with only like 1% waste heat?

Will the hull still glow? Hope not lol... crew would get broiled alive even if the hull is unobtanium that won't melt.

 

What about just using chemical thrusters to hover over the ocean and then flip to use the Blowtorch drive from there?

Surely the ocean can take it... it's gonna make an epic splash though.

 

This is not like Firefly... but we are seeing what would happen if we could do stuff like that.

 

Originally I wanted an SSTO simply for trade..  like it would be cool to have as many spaceports on a planet as airports.

But with SSTOs this dangerous, I reckon doing that would be insane and be regulated with as much red tape as possible.

Likely have only a few international spaceports on a given planet near metropolitan cities or capitols.

 

So the ultimate appeal of SSTO's, to go and come as you please... does not really allow for that without getting a minimum distance from the ground before flipping and ingniting a plume of doom behind you.

 

Question: Assuming land launch, what is the minimum distance required on ascent using chemical rockets before flipping to engage the uber plasma rocket?

I reckon the overall mass of the ship to propellant ratio would be greater than 10%, inasmuch the chemical dual axis belly thrusters must vertically launch the ship high enough into the atmosphere where the ship can flip it's nose upward and not nuke blast the ground with it's plume.

 

Even then, I reckon a super plume like this would cause shockwaves on the ground that normal rockets leave... but at a farther distance.

 

So seeing it in the far distance and being under it would get someone blown away lol.

 

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23 minutes ago, Spacescifi said:

Wow... so I guess a scifi torchship would need 99.99 efficiency with only like 1% waste heat?

Will the hull still glow? Hope not lol... crew would get broiled alive even if the hull is unobtanium that won't melt.

Well, 99.99% efficiency would be 0.01% waste heat. But there is a thermodynamic limit to the maximum efficiency of a magnetohydrodynamic thruster, somewhere around 87% even with superconductors. So you're not getting rid of that heat. 

In any event, what you are describing is not a magnetohydrodynamic thruster at all, anymore. You just have a pure fusion rocket, with liquid hydrogen going in one side and disassociated deuterium plasma coming out the other side. Sufficient inertial confinement for proton-proton fusion is something that even a star struggles to accomplish (the mean time for any proton to undergo fusion with another proton in our sun is on the order of 9 billion years).

3 hours ago, Spacescifi said:

What about just using chemical thrusters to hover over the ocean and then flip to use the Blowtorch drive from there?

Surely the ocean can take it... it's gonna make an epic splash though.

In a vertical-takeoff ascent, the thrust line of the main engines will intersect the surface for somewhere between 90-150 seconds. Let's say 100 seconds. In that time, the plume will dump approximately ten megatons TNT equivalent into the surface of the Earth, and it will do so using relativistic particles. If this occurs over the ocean, it will vaporize 4.7e9 kilograms of water (that's based on enthalpy of vaporization; heat capacity is a rounding error at this point), producing a superheated steam explosion approximately 35 kilometers in diameter.

3 hours ago, Spacescifi said:

Originally I wanted an SSTO simply for trade..  like it would be cool to have as many spaceports on a planet as airports.

But with SSTOs this dangerous, I reckon doing that would be insane and be regulated with as much red tape as possible.

This is not an SSTO. This is a super fusion torchship which can leave Earth, fly to Pluto, land, and come back to Earth on a single tank of fuel. This is not part of any SSTO class of vehicles.

4 hours ago, Spacescifi said:

Question: Assuming land launch, what is the minimum distance required on ascent using chemical rockets before flipping to engage the uber plasma rocket?

With exhaust traveling at 0.3% of the speed of light, I would say you should be at least as far away as the moon before you point your engine toward Earth.

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Y

1 hour ago, sevenperforce said:

Well, 99.99% efficiency would be 0.01% waste heat. But there is a thermodynamic limit to the maximum efficiency of a magnetohydrodynamic thruster, somewhere around 87% even with superconductors. So you're not getting rid of that heat. 

In any event, what you are describing is not a magnetohydrodynamic thruster at all, anymore. You just have a pure fusion rocket, with liquid hydrogen going in one side and disassociated deuterium plasma coming out the other side. Sufficient inertial confinement for proton-proton fusion is something that even a star struggles to accomplish (the mean time for any proton to undergo fusion with another proton in our sun is on the order of 9 billion years).

In a vertical-takeoff ascent, the thrust line of the main engines will intersect the surface for somewhere between 90-150 seconds. Let's say 100 seconds. In that time, the plume will dump approximately ten megatons TNT equivalent into the surface of the Earth, and it will do so using relativistic particles. If this occurs over the ocean, it will vaporize 4.7e9 kilograms of water (that's based on enthalpy of vaporization; heat capacity is a rounding error at this point), producing a superheated steam explosion approximately 35 kilometers in diameter.

This is not an SSTO. This is a super fusion torchship which can leave Earth, fly to Pluto, land, and come back to Earth on a single tank of fuel. This is not part of any SSTO class of vehicles.

With exhaust traveling at 0.3% of the speed of light, I would say you should be at least as far away as the moon before you point your engine toward Earth.

 

Okay..... I do not give up easily. There may be a loophole yet.

VASIMIR is supposed to be great at throttling it's thrust down or up right?

So let's say the scifi SSTO can do that too as well.

Of course it lowers propellant efficiency but also engine heat, meaning more propellant is spent getting to LEO and also the exhaust speed is lower.

 

Now... this is the hard part.

What is the sweet spot exhaust speed that will allow the destroyer weighted spaceship into orbit under it's own power while not nuking the planet.?

The way  see it, yes the SSTO will have a lot less propellant once it reaches space, but it's engine can make up for it in space anyway.

 

The only reason I designed the engines to be so uber was because I wanted enough efficiency for multiple course corrections in space without refueling as well as a possible landing.

But the way the numbers look, I am thinking it would be better to just second stage it.

The first stage would be the largest ever though.

Also, the second stage would have have to flip so as to point the engine at space only. Since the plume would kill the first stage if it hit it.

 

I think the SSTO ability is nice to have, including the abiity to throttle it down to more... chemical rocket like efficiency.

 

I think that perhaps if the efficiecy is better than chemical but not too much better it could allow for a safer SSTO.

 

Sigh.... it seems SSTOs only make sense on non-inhabited low gravity worlds... or ones that have dedicated spaceports that will launch a first stage into orbit to bring you down to the spaceport.

 

So much for scifi classic SSTOs.

 

Ironically the lower mass ships, assuming the same engine, would require less power to reach the same efficiency... but that is not much of solution to the real problem if the sheer lethality of it all.

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2 hours ago, Spacescifi said:

VASIMIR is supposed to be great at throttling it's thrust down or up right?

So let's say the scifi SSTO can do that too as well.

VASMIR doesn't throttle its thrust so much as it has the ability to shift gears. It can produce high thrust with low specific impulse or low thrust with high specific impulse.

VASMIR is not the only engine that can do this. Even the F-1 engine on the Saturn V could adjust its mixture ratio in flight, using more oxidizer at launch for greater thrust and less near the end of the burn for greater specific impulse. That (along with a larger Descent Engine nozzle) is how they were able to add enough dV to send rovers to the moon without adding any fuel.  Certain nuclear thermal rocket designs do this as well, pumping liquid oxygen into the nozzle to add thrust but decrease propellant velocity.

2 hours ago, Spacescifi said:

What is the sweet spot exhaust speed that will allow the destroyer weighted spaceship into orbit under it's own power while not nuking the planet.?

There isn't one. Not because engines can't "shift gears" but because what you're describing is a physics-breaking monstrosity which cannot exist. Something which cannot exist cannot have properties subject to probing by the laws of physics.

2 hours ago, Spacescifi said:

The only reason I designed the engines to be so uber was because I wanted enough efficiency for multiple course corrections in space without refueling as well as a possible landing.

Not to be pedantic, but you haven't really designed anything. You've simply stated a series of specifications which cannot all be simultaneously true.

What course corrections do you need? No one needs multiple hours of one-gee thrusting for course corrections. If your story needs abrupt course corrections then simply have it carry a little more propellant. No one is going to be adding up how much propellant you have used.

3 hours ago, Spacescifi said:

Sigh.... it seems SSTOs only make sense on non-inhabited low gravity worlds... or ones that have dedicated spaceports that will launch a first stage into orbit to bring you down to the spaceport.

So much for scifi classic SSTOs.

What you have described is nothing like a scifi classic SSTO, so I'm not sure why you would apply its properties to SSTOs.

3 hours ago, Spacescifi said:

Ironically the lower mass ships, assuming the same engine, would require less power to reach the same efficiency... but that is not much of solution to the real problem if the sheer lethality of it all.

No, they would have the same power to mass requirements. Clustering is key.

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There is no loophole you could find that any number of substantially smarter people than us haven't. I do not mean to be rude here, but this is not a case of doing something nobody has done yet, it is a case of not understanding physics. What you are describing cannot physically exist, because physics itself does not allow it.

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All of these questions, @Spacescifi, sound a little like asking, “If people could fly like Superman, how high could they fly if they only ate cereal?”

There is so much undefined about this question that it is not only impossible to answer, but there is no set of assumptions or other ideas which can be adopted to make the question make sense.

The problem is not that the question invokes a fictional character with fictional abilities; that’s fine. The problem is that it attempts to connect physical reality to that fiction in a way that doesn’t make sense. If people could fly like Superman, then they would have the flight powers of Superman; there is nothing in either the fictional DC Comics world or the physical world where a cereal diet has a relationship to maximum altitude. It’s just undefined, like dividing by zero or trying to find the last digit of pi.

If you want to write a story with a spaceship, that’s great. But let the plot dictate what your spaceship needs to do, not the other way around. 

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