Heaviest possible SSTO

[Spacescifi]

 

So I looked up schemes for an air breathing antimatter SSTO. According to the researched PDF, the heaviest vessel one could lift with an antimatter rocket without having massive speed losses due to extra cooling resources would weigh about this. About a 500 ton SSTO.

One that relied mostly on intake air with antimatter would need to be sleeker to escape the atmosphere faster. Burning more antimatter for more thrust won't work, as the cooling equipment required would cancel out the thrust benefits.

Any vessel heavier than a passenger jet would need rocket staging to reach orbit or risk being too heavy with cooling equipment or blowing up midflight due to heat from using extra antimatter for thrust for lack of staging.

 

So for a full on scifi example:

To lift something like this into orbit most efficiently, you would need air breathing antimatter rocket staging.

Edited September 18, 2019 by Spacescifi

[ThatGuyWithALongUsername]

I'm not sure there's a limit to the heaviest theoretically possible SSTO, just keep scaling up until you accidentally have a space elevator I guess? Not sure what this post is trying to say?

[Spacescifi]

12 minutes ago, ThatGuyWithALongUsername said:

I'm not sure there's a limit to the heaviest theoretically possible SSTO, just keep scaling up until you accidentally have a space elevator I guess? Not sure what this post is trying to say?

 

That flying heavy starships into orbit like SSTO's that weigh as much as a destroyer is not possible even with antimatter rocketry.

Here is the article with research.

https://kundoc.com/pdf-investigation-of-antimatter-air-breathing-propulsion-for-single-stage-to-orbit-s.html

[Signo]

Before JJ Abrams the Enterprise was built by a orbital dock. Now beam me up.

[Spacescifi]

7 minutes ago, Signo said:

Before JJ Abrams the Enterprise was built by a orbital dock. Now beam me up.

 

While theoretically possible, that method would take so long that I would wonder hiw starfleet ever built a big fleet.

When you have access to copious amounts of antimatter in a setting, why not use it for reaching space more effectively?

[Signo]

Man, it is Star Trek, they have replicators. They do not need to lift stuff to orbit. Stuff is freely "generated". 

Replicator, a vodka martini. Shaken, not stirred.

[sevenperforce]

No fully-airbreathing SSTO is possible, since you need to circularize once out of the atmosphere, and you cannot do that without reaction mass. Accordingly, you will always need some sort of propellant for the final orbital insertion. Building a vehicle becomes an optimization problem between retaining airbreathing capability for as long as possible and not wasting too much fuel fighting drag and heat rejection issues.

I can build an SSTO that spams air-locked RAPIERs and can reach almost to Kerbin orbit -- such that I need only a Sepratron to circularize -- but I could do it more efficiently by using fewer RAPIERs and carrying a bit of regular liquid bipropellant.

A simple liquid-core antimatter rocket using methane, ammonia, or even plain water can nearly make orbit twice in a day without refueling, so if you just built that with an air intake, you could do it every day and twice on the weekends, no problem. There's really no maximum possible size other than the constraints of your materials.

[kerbiloid]

Is moving a planet from beneath the ship counted as SSTO ship or SSTO planet?

[Nothalogh]

5 hours ago, Spacescifi said:

 

So I looked up schemes for an air breathing antimatter SSTO. According to the researched PDF, the heaviest vessel one could lift with an antimatter rocket without having massive speed losses due to extra cooling resources would weigh about this. About a 500 ton SSTO.

One that relied mostly on intake air with antimatter would need to be sleeker to escape the atmosphere faster. Burning more antimatter for more thrust won't work, as the cooling equipment required would cancel out the thrust benefits.

Any vessel heavier than a passenger jet would need rocket staging to reach orbit or risk being too heavy with cooling equipment or blowing up midflight due to heat from using extra antimatter for thrust for lack of staging.

 

So for a full on scifi example:

To lift something like this into orbit most efficiently, you would need air breathing antimatter rocket staging.

I believe the user @sevenperforce made a thoroughly informative thread on the subject of "how to build a scifi tier SSTO", a couple years ago.

[sevenperforce]

4 minutes ago, Nothalogh said:

I believe the user @sevenperforce made a thoroughly informative thread on the subject of "how to build a scifi tier SSTO", a couple years ago.

I did?

Now I need to go hunt it down.....

[Nothalogh]

1 minute ago, sevenperforce said:

I did?

Now I need to go hunt it down.....

It was a TOTM, it involved a Nuclear Thermal TBCC Air+Water Augmented Turborocket

[sevenperforce]

3 minutes ago, Nothalogh said:

It was a TOTM, it involved a Nuclear Thermal TBCC Air+Water Augmented Turborocket

Ah, here it was.

It's a shame the images died.

[Nothalogh]

Just now, sevenperforce said:

Ah, here it was.

It's a shame the images died.

Yeah, it was glorious

[Spacescifi]

55 minutes ago, sevenperforce said:

No fully-airbreathing SSTO is possible, since you need to circularize once out of the atmosphere, and you cannot do that without reaction mass. Accordingly, you will always need some sort of propellant for the final orbital insertion. Building a vehicle becomes an optimization problem between retaining airbreathing capability for as long as possible and not wasting too much fuel fighting drag and heat rejection issues.

I can build an SSTO that spams air-locked RAPIERs and can reach almost to Kerbin orbit -- such that I need only a Sepratron to circularize -- but I could do it more efficiently by using fewer RAPIERs and carrying a bit of regular liquid bipropellant.

A simple liquid-core antimatter rocket using methane, ammonia, or even plain water can nearly make orbit twice in a day without refueling, so if you just built that with an air intake, you could do it every day and twice on the weekends, no problem. There's really no maximum possible size other than the constraints of your materials.

 

It depends on the weight of the spacecraft, and how heat resistant the hull is. If both are what is required, then even an only air breathing spacecraft could reach orbital velocity.

That is the idea behind scram jet SSTO's. Although I will grant you that having extra fuel for more fine control of orbital insertion is always a good idea.

Size matters because greater size requires higher thermal energy within the engine. Which limits how heavy a spacecraft you can send up to orbit or else.... BOOM! Unless you do it with rocket stages.

Alternately we could just use pusher plate propulsion. But that is not part of the discussion.

Edited September 19, 2019 by Spacescifi

[Incarnation of Chaos]

Once you get to the point where you have antimatter, fusion and other science-fiction staples i always figured it would be far more prudent to just use superconductors to generate a strong enough magnetic field to repel the planetary field and essentially bounce any large ship into orbit and then use AM engines to actually perform a insertion burn. Now i haven't the slightest clue if this would be actually possible or done the math behind it but i think the entire idea of using a traditional rocket at this point is kinda silly due to the tech implied.

[Nothalogh]

27 minutes ago, sevenperforce said:

Ah, here it was.

It's a shame the images died.

Also, this thread, quoted within that one, contains a relevant goldmine.

 

[sevenperforce]

14 minutes ago, Spacescifi said:

It depends on the weight of the spacecraft, and how heat resistant the hull is. If both are what is required, then even an only air breathing spacecraft could reach orbital velocity.

That is the idea behind scram jet SSTO's. Although I will grant you that having extra fuel for more fine control of orbital insertion is always a good idea.

You cannot reach a velocity in an airbreather which is substantially greater than the actual exhaust velocity of your engine.

And even if you use antimatter to boost up the exhaust velocity so you can reach orbital velocity in-atmo, that doesn't get you into orbit. It's not about "extra fuel" for "more fine control" of orbital insertion; it's the fact that orbital insertion itself requires a separate rocket engine.

[Spacescifi]

1 hour ago, Incarnation of Chaos said:

Once you get to the point where you have antimatter, fusion and other science-fiction staples i always figured it would be far more prudent to just use superconductors to generate a strong enough magnetic field to repel the planetary field and essentially bounce any large ship into orbit and then use AM engines to actually perform a insertion burn. Now i haven't the slightest clue if this would be actually possible or done the math behind it but i think the entire idea of using a traditional rocket at this point is kinda silly due to the tech implied.

 

That is an interesting thought. Here is what I read:

Magnetic fields can repel all matter that is not ferromagnetic (metals pulled by magnets). Diamagnetism I believe is what you're referring to. Shown below.

Water is diamagnetic enough that you can float it in a strong magnetic field, and frogs definitely have plenty of water in their bodies smd aren't heavy either.

Now as far as I have read, projecting magnetic fields kilometers out while maintaining field strength is not something I have seen anyone theorize on a means of how to do it.

One could throw more power at the challenge via antimatter, but again material constraints ruin the dream.

Electromagnetic coils have been known to mechanically snap when generating extremely high Tesla strong magnetic fields. Momentarily at that.

In other words, too much magnetism will break a magnet's parts. Unless we figure a way around that too. Perhaps through more flexible coil material that will bend instead of snap under the pressure. Once that is solved, then you have to figure out how to project a magnetic field 100 kilometers out to repel against the planet's surface.

No? Perhaps you can repel the planet's air magnetically? That would be great, but would stiil require a realky large magnetic field projected out to perhaps 25 kilometers.

Also make sure no metal is in range. It would be like shooting the ship.

Edited September 19, 2019 by Spacescifi

[Incarnation of Chaos]

1 minute ago, Spacescifi said:

 

That is an interesting thought. Here is what I read:

Magnetic fields can repel all matter that is not ferromagnetic (metals pulled by magnets. Diamagnetism I believe is what you're referring to. Shown below.

Water is diamagnetic enough that you can float it in a strong magnetic field, and frogs definitely have plenty of water in their bodies smd aren't heavy either.

Now as far as I have read, projecting magnetic fields kilometers out while maintaining field strength is not something I have seen anyone theorize on a means of how to do it.

One could throw more power at the challenge via antimatter, but again material constraints ruin the dream.

Electromagnetic coils have been known to mechanically snap when generating extremely high Tesla strong magnetic fields. Momentarily at that.

In other words, too much magnetism will break a magnet's part. Unless we figure a way around that too. Perhaps through more flexible coil material that will bend instead of snap under the pressure. Once that is solved, then you have to figure out how to project a magnetic field 100 kilometers out to repel against the planet's surface.

No? Perhaps you can repel the planet's air magnetically? That would be great, but would stiil require a realky large magnetic field projected out to perhaps 25 kilometers.

Also make sure no metal is in range. It would be like shooting the ship.

The way i was thinking was essentially the ship would need to be built to be electrically isolated from the enviroment; essentially a massive faraday cage with only the needed conduits to allow the fields to escape and nothing else. So because the majority of the ship was isolated from the fields; it could "Float" on them if you could manage to direct the majority of the magnetism downwards. Essentially the ship is repelling it's self and any interaction with the planetary field is gravy; but you're correct in that there's a massive amount of engineering challenges to be solved before this even becomes an option.

Also the electromagnets would likely be Graphene or Carbon nanotubes; some species are superconducting. Perhaps you could exploit that? Instead of brute-forcing it and repelling the surface of the planet you have the bottom of the ship made of superconductors which would reject any magnetic field below them providing a down force?

Also yeah; no ferrous materials on the crew especially. Iv'e heard horror stories from MRI operators; this would be literally magnitudes of order worse.

[Spacescifi]

12 minutes ago, Incarnation of Chaos said:

The way i was thinking was essentially the ship would need to be built to be electrically isolated from the enviroment; essentially a massive faraday cage with only the needed conduits to allow the fields to escape and nothing else. So because the majority of the ship was isolated from the fields; it could "Float" on them if you could manage to direct the majority of the magnetism downwards. Essentially the ship is repelling it's self and any interaction with the planetary field is gravy; but you're correct in that there's a massive amount of engineering challenges to be solved before this even becomes an option.

Also the electromagnets would likely be Graphene or Carbon nanotubes; some species are superconducting. Perhaps you could exploit that? Instead of brute-forcing it and repelling the surface of the planet you have the bottom of the ship made of superconductors which would reject any magnetic field below them providing a down force?

Also yeah; no ferrous materials on the crew especially. Iv'e heard horror stories from MRI operators; this would be literally magnitudes of order worse.

 

That sounds interesting. If a faraday cage can float merely by directing magnetice force downward (without resorting to uber powerful diamagnetic fields) then perhaps we could do that.

Most matter is only weakly diamagnetic, so it takes a strong field to show it.

As for strong magnetic fiels being dangerous to life, I read online that some stars, I think neutron stars, are so magnetic that if you got close enough (assuming you're were not burned up already), your flesh would liquify, leaving only bone.

Don't ask me why. Something to do with uber magnetic fields do weird stuff at high levels.

[Incarnation of Chaos]

2 minutes ago, Spacescifi said:

 

That sounds interesting. If a faraday cage can float merely by directing magnetice force downward (without resorting to uber powerful diamagnetic fields) then perhaps we could do that.

Most matter is only weakly diamagnetic, so it takes a strong field to show it.

As for strong magnetic fiels being dangerous to life, I read online that some stars, I think neutron stars, are so magnetic that if you got close enough (assuming you're were not burned up already), your flesh would liquify, leaving only bone.

Don't ask me why. Something to do with uber magnetic fields do weird stuff at high levels.

That's one of the other reasons i want the ship to basically be a faraday cage; space has magnetic fields that will literally rip the iron out of your hemoglobin. What i really need is a math equasion to relate the field strength to a down force; until then it's just conjecture. Though i'm pretty sure a pure faraday cage wouldn't float; since it uses the edge effect to distribute the field around it's self. So the net force would be 0; you need something to repel or expel the field lines to actually float. But you still need the ship to be isolated electrically because otherwise aside from crew/health issues you also run into the issue of the ship it's self getting magnetized.

[Nothalogh]

Also, @sevenperforce , just reading the phrase:

Quote

nuclear-thermal turbocharged ramrocket engine

It brings a tear of joy to my eye.

[sevenperforce]

4 hours ago, Incarnation of Chaos said:

The way i was thinking was essentially the ship would need to be built to be electrically isolated from the enviroment; essentially a massive faraday cage with only the needed conduits to allow the fields to escape and nothing else. So because the majority of the ship was isolated from the fields; it could "Float" on them if you could manage to direct the majority of the magnetism downwards. Essentially the ship is repelling it's self and any interaction with the planetary field is gravy...

Also the electromagnets would likely be Graphene or Carbon nanotubes; some species are superconducting. Perhaps you could exploit that? Instead of brute-forcing it and repelling the surface of the planet you have the bottom of the ship made of superconductors which would reject any magnetic field below them providing a down force?

That would get you into reactionless-thruster land. You gotta push against something (planetary magnetic field, atmosphere, etc.) or nothing happens. 

I was actually like 13 or 14 and designed a magnetic "flying saucer" that used gyrostabilizers and a superconducting magnetic repulsor field. The idea was to push against the Earth's magnetic field and hover. When I got a little older, took physics, and did the math, I learned that my idea would have worked...it just would have required exhorbitant amounts of electrical energy. Earth's magnetic field is immense, but very diffuse; levitating any sort of manned flying machine would require creating a magnetic field something like the size of Brazil.

4 hours ago, Nothalogh said:

Also, @sevenperforce , just reading the phrase:

Quote

nuclear-thermal turbocharged ramrocket engine

It brings a tear of joy to my eye.

Such a thing of beauty.

I wonder if I have those pixel drawings somewhere. I was using postimg to host them and evidently that was a bad idea.

Of all the possible configurations, I believe that the LANTTCRR (LOX-augmented nuclear-thermal turbocharged ramrocket) running on an exotic carbide-alloy pebble-bed reactor burning either hydrazine or ammonia ends up resulting in one of the smallest vehicle cross-sections for an SSTO. Methane has a better mass fraction but I think ends up being larger. LH₂ may squeeze out a slightly higher mass fraction than methane but is prohibitively larger.

[kerbiloid]

Spoiler

"nuclear-thermal turbocharged ramrocket engine"
probably looks the best in German.

 

[sevenperforce]

18 minutes ago, kerbiloid said:

"nuclear-thermal turbocharged ramrocket engine"
probably looks the best in German.

Mitflüssigemsauerstoffangereichertethermischaufgeladenekernramrakete.