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Best Spaceship We Could Build Now


Spacescifi
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It seems to me that the best we could do is mix project Orion with SpaceX Starship.

 

Basically launch the thing off of a superheavy half tube maglev rail into the air at 500 mph, then do the pusher plate detonations to orbit.

 

Why maglev? Easy repeat launches.

 

To get back we could use Elon's starship as the second stage for the Orion and deorbit and land.

If we had antimatter bombs it would simply mean that we could launch ever heavier, larger things into orbit.

Pusher plate drive section just stays in orbit, waiting to redock with starship.

 

Staging is NEVER going away it seems... and if it does, it won't look like a rocket.

 

And if we wanted to be really fancy, we could land starship on a maglev runway to slow it down like a plane.

Edited by Spacescifi
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21 minutes ago, Spacescifi said:

If we had antimatter bombs it would simply mean that we could launch ever heavier, larger things into orbit.

Pusher plate drive section just stays in orbit, waiting to redock with starship.

Using a pusher-plate with antimatter is about as smart as throwing packages of c-4 out the back of a chemical rocket.

It only makes sense for nuclear bombs because:

1) the cost and weight of a nuclear bomb is about the same regardless of total energy output

2) nuclear bombs have a minimum effective size that is too large to be contained by current materials(at least light enough materials to use on a rocket)

Neither of these is true for antimatter, so a pusher-plate design is highly unlikely to be in any way efficient for any antimatter powered rocket.

 

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If you're doing Project Orion on Earth, that extra 200 m/s from the rail is barely going to affect how much you need to accelerate with the rocket, and it won't stop any nuclear debris from circulating in the atmosphere. You may as well detonate your nukes right on the ground, or over the ocean if we're feeling extra careless about the environment. 

Rail launch to orbit is a decent idea on the Moon, but not on anything much bigger than the Moon, and especially not anyplace with air. Orion is a good idea anywhere that isn't near Earth.

Giant chemical rockets are as good as we've got right now for getting into Earth orbit. We can make those reusable and assemble larger structures in orbit if we need to, and then go with nuclear thermal or ion propulsion for high Isp.

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The best we could do now?

With some development a lofted boosted fission Mini-Mag Orion is probably doable. Then getting anywhere in the Solar System is possible, even a Pluto sample return could be done.

Personally I think delivering large scientific probes to every planet would be desirable, and potentially fleets of orbiters to the gas/ice giants. And of course landers/rovers for as many bodies as practical. Exploration of Titan seems like one of the more interesting ones - aircraft, ground vehicles, and "watercraft" are all possible. High detail gravity maps of every planet and their moons. And of course manned missions to Mars and maybe even Jupiter.

The only issues will be the massive influx of charged particles in the magnetic field - though this may not be nearly as bad as a conventional Orion. Maybe a slight increase in the background radiation around Earth. However one advantage of the Mini-Mag Orion is that its performance is so high that this increase is not a problem.

We have the "technology" to do this, but it requires significant RnD, and may take a good amount of time to actually develop. Still, it could be worth doing.

 

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It all depends on how you define "best", "spaceship", and "now".

Best could mean the most cost effect way of achieving a desired goal (either per unit cost, cycle cost, operational cost, or development cost). Best can also mean having the largest payload fraction, the smallest fuel fraction, lowest environmental impact, highest throughput (payload mass per day), most scientific versatility, or simply the largest. 

Spaceship also has various possible interpretations. It could be a vehicle for surface to orbit transport, orbital transport, interplanetary transport, or a lander. It could be used strictly for cargo, crew, fuel, or perform some other function like scientific research, or ISRU, or industrial manufacturing.

Now is also a surprisingly flexible term in terms of spaceflight. It could limit things to existing craft, those currently in development, those that could be made with existing facilities. Anything beyond that would require significant R&D time, even just with preexisting space proven technologies, and is too far removed to be considered "now". Despite that, some might still consider craft made with flight proven technologies, or with technologies that have been demonstrated on a smaller scale as "now".

 

In terms of surface to orbit vehicles:

As far as today today: the Long March Family of rockets probably has the highest throughput to both LEO and GEO, the Delta IV M+(4,2) has the highest payload fraction, Falcon heavy has the highest LEO capacity, and either Falcon Heavy or Delta IV Heavy has the highest GTO capacity (depending on who you believe). And either Atlas V 431 or Falcon Heavy has the best price per kilogram to LEO (again, depending on who you believe)

In terms of what is being developed: New Glen, Vulcan, Starship, or the Long March family will have the highest throughput (its hard to say at this point), Vulcan will have the best payload fraction, either SLS Block 2 or Long March 9 will have the highest LEO and GTO capacity (depending on if the block 2 uses the pyrios boosters, and if the Long March 9's upper stage is hydrolox), and  either Vulcan ACES, New Glen, or Starship will have the best price per kilogram to LEO (depending on pricing and market forces)

As to what we can do with flight proven technologies, not much better. Most demoed propulsion systems have been for deep space, and have little use in surface to orbit transport. Maglevs as currently demonstrated can't provide enough velocity to warrant use for non spaceplanes, as they can only provide near horizontal velocity and reorienting a rocket for vertical flight could cause massive aerodynamic loads. In anycase, there are issues with large loads for current maglev systems (which is why they aren't used for freight) which would exclude their use in spaceflight for everything but smallsat launches.

For demonstrated, but not flight proven technologies; a superheavy chemical rocket like the original ITS will still have the highest LEO and GTO capacity, a laser thermal rocket would have the highest payload fraction and cost per kilogram, an airbreathing spaceplane TSTO would probably have the most throughput.

Orion was never demoed with nuclear weapons, and was also deemed unfit as a first stage (sound reverberations from the first explosion would shred the craft). Nerva has a stupid low TWR and specific power. The Timberwind NTRs were never demoed, and their values were likely exaggerated to garner additional funding (not that that helped in the end). Minmag Orion testing was inconclusive, used non-fissile materials, and may be incompatible with maglevs from magnetic interference.

If development and deployment time is ignored for "Now", as long as the technology has been demonstrated, than dynamic orbital rings are the best. They can be made with current materials (no nanotubes, graphene, room temp superconductors, fusion or anything like that), only need power (which they could easily make on sight with solar), can take several megatons to orbit per day, kilotons per trip, and all for a few cents per kilo.

Hope this helps.

 

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probably old boom boom. granted you would need to have everyone hand over their nuclear warheads so you can reprocess the plutonium to make pulse units. the thing i have doubts about is the shock absorber, not the engine itself. 

7 hours ago, Terwin said:

Using a pusher-plate with antimatter is about as smart as throwing packages of c-4 out the back of a chemical rocket.

It only makes sense for nuclear bombs because:

1) the cost and weight of a nuclear bomb is about the same regardless of total energy output

2) nuclear bombs have a minimum effective size that is too large to be contained by current materials(at least light enough materials to use on a rocket)

Neither of these is true for antimatter, so a pusher-plate design is highly unlikely to be in any way efficient for any antimatter powered rocket.

 

an antimatter engine is likely going to be operated at steady state. reacting very small amounts of antimatter over time, completely eliminating the need for a pusher plate. i cant help but think it would work better with a magnetic nozzle. nukes have the opposite problem, the whole reason behind the pusher plate is that nuclear warheads like to put a lot of energy out at once and there is no way to run them steady state with the same specific impulse. with antimatter you can better control flow rates and can opt for a far far safer long burn. all those repetitive shocks is likely going to make their antimatter particles skip out their containment, and the first thing they will encounter and destroy is the containment system.

that said we are nowhere near the level of technology needed for antimatter propulsion. if we could have sufficiently good containment we would be able to have breakeven fusion reactors. were also going to need the experience of operating fusion reactors to figure out where all the gotchas are. when we can contain normal matter well enough so the escapees can't destroy the reactor, then we can do it with antimatter. i also dont think antimatter will be useful as anything other than energy storage. the energy needed to make it will likely come from fusion, so why not just have a fusion engine?

Edited by Nuke
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7 hours ago, wafflemoder said:

It all depends on how you define "best", "spaceship", and "now".

Best could mean the most cost effect way of achieving a desired goal (either per unit cost, cycle cost, operational cost, or development cost). Best can also mean having the largest payload fraction, the smallest fuel fraction, lowest environmental impact, highest throughput (payload mass per day), most scientific versatility, or simply the largest. 

Spaceship also has various possible interpretations. It could be a vehicle for surface to orbit transport, orbital transport, interplanetary transport, or a lander. It could be used strictly for cargo, crew, fuel, or perform some other function like scientific research, or ISRU, or industrial manufacturing.

Now is also a surprisingly flexible term in terms of spaceflight. It could limit things to existing craft, those currently in development, those that could be made with existing facilities. Anything beyond that would require significant R&D time, even just with preexisting space proven technologies, and is too far removed to be considered "now". Despite that, some might still consider craft made with flight proven technologies, or with technologies that have been demonstrated on a smaller scale as "now".

 

In terms of surface to orbit vehicles:

As far as today today: the Long March Family of rockets probably has the highest throughput to both LEO and GEO, the Delta IV M+(4,2) has the highest payload fraction, Falcon heavy has the highest LEO capacity, and either Falcon Heavy or Delta IV Heavy has the highest GTO capacity (depending on who you believe). And either Atlas V 431 or Falcon Heavy has the best price per kilogram to LEO (again, depending on who you believe)

In terms of what is being developed: New Glen, Vulcan, Starship, or the Long March family will have the highest throughput (its hard to say at this point), Vulcan will have the best payload fraction, either SLS Block 2 or Long March 9 will have the highest LEO and GTO capacity (depending on if the block 2 uses the pyrios boosters, and if the Long March 9's upper stage is hydrolox), and  either Vulcan ACES, New Glen, or Starship will have the best price per kilogram to LEO (depending on pricing and market forces)

As to what we can do with flight proven technologies, not much better. Most demoed propulsion systems have been for deep space, and have little use in surface to orbit transport. Maglevs as currently demonstrated can't provide enough velocity to warrant use for non spaceplanes, as they can only provide near horizontal velocity and reorienting a rocket for vertical flight could cause massive aerodynamic loads. In anycase, there are issues with large loads for current maglev systems (which is why they aren't used for freight) which would exclude their use in spaceflight for everything but smallsat launches.

For demonstrated, but not flight proven technologies; a superheavy chemical rocket like the original ITS will still have the highest LEO and GTO capacity, a laser thermal rocket would have the highest payload fraction and cost per kilogram, an airbreathing spaceplane TSTO would probably have the most throughput.

Orion was never demoed with nuclear weapons, and was also deemed unfit as a first stage (sound reverberations from the first explosion would shred the craft). Nerva has a stupid low TWR and specific power. The Timberwind NTRs were never demoed, and their values were likely exaggerated to garner additional funding (not that that helped in the end). Minmag Orion testing was inconclusive, used non-fissile materials, and may be incompatible with maglevs from magnetic interference.

If development and deployment time is ignored for "Now", as long as the technology has been demonstrated, than dynamic orbital rings are the best. They can be made with current materials (no nanotubes, graphene, room temp superconductors, fusion or anything like that), only need power (which they could easily make on sight with solar), can take several megatons to orbit per day, kilotons per trip, and all for a few cents per kilo.

Hope this helps.

 

 

8 hours ago, Bill Phil said:

The best we could do now?

With some development a lofted boosted fission Mini-Mag Orion is probably doable. Then getting anywhere in the Solar System is possible, even a Pluto sample return could be done.

Personally I think delivering large scientific probes to every planet would be desirable, and potentially fleets of orbiters to the gas/ice giants. And of course landers/rovers for as many bodies as practical. Exploration of Titan seems like one of the more interesting ones - aircraft, ground vehicles, and "watercraft" are all possible. High detail gravity maps of every planet and their moons. And of course manned missions to Mars and maybe even Jupiter.

The only issues will be the massive influx of charged particles in the magnetic field - though this may not be nearly as bad as a conventional Orion. Maybe a slight increase in the background radiation around Earth. However one advantage of the Mini-Mag Orion is that its performance is so high that this increase is not a problem.

We have the "technology" to do this, but it requires significant RnD, and may take a good amount of time to actually develop. Still, it could be worth doing.

 

 

9 hours ago, cubinator said:

If you're doing Project Orion on Earth, that extra 200 m/s from the rail is barely going to affect how much you need to accelerate with the rocket, and it won't stop any nuclear debris from circulating in the atmosphere. You may as well detonate your nukes right on the ground, or over the ocean if we're feeling extra careless about the environment. 

Rail launch to orbit is a decent idea on the Moon, but not on anything much bigger than the Moon, and especially not anyplace with air. Orion is a good idea anywhere that isn't near Earth.

Giant chemical rockets are as good as we've got right now for getting into Earth orbit. We can make those reusable and assemble larger structures in orbit if we need to, and then go with nuclear thermal or ion propulsion for high Isp.

As a scifi writer, 'best spaceship' means anything that can fulfill the Star Trek mandate:

"To seek new life and civilizations, to boldly go where no man has gone before."


Granted, I concede that I WILL use make believe for crossing interstellar and interplanetary distances in a reasonable amounts of time,  but the STL propulsion methods need not be make-believe.


As for my methods, the point of launching the Orion off the maglev at 500 mph is twofold:

1. Do not destroy the launch site.

2. Save propellant for when I really need it... like refueling my stage 2 detachable SpaceX Starship when it comes to redock in orbit after a planetary mission.

To be clear, my spaceship ideal is as if we wedded project Orion to SpaceX. Two ships in one.

 It uses the best of both, since it can lift far more than a SpaceX Starship ever could, and also can do SSTO landings via SpaceX Starship and take off back to orbit which Project Orion would have serious difficulty to pull off if at all in one piece.

Minimag I have heard positive things about, but it seems to me to be more a space only engine. Remember my idea of 'best spaceship' as a scifi writer is NOT the ship that has ultra efficient engines that can crawl from Earth to Mars in 6 months. Scifi solves that quicker with make-believe. I am interested in going to places of interest... Earth worlds, asteroid mines, Mars worlds, gas giant ballon gas refinery stations, stuff like that.


The only place where real physics comes into play is where it CAN solve the problem of liftoff, orbit, and reentry.

Which is exactly what my idea of 'best spaceship' was designed to do.

Regarding the minimag VS project Orion discussion, I tend to favor Orion since Orion can put more tons in orbit in a single launch than minimag can.

Minimag I wonder if it can even survive launch using the minimag engines. They are magnetic, and shooting out fission or fusion exhaust with a magnetic nozzle in the air might degrade the magnetic nozzle since air conducts heat. Vacuum won't have that issue, but I digress.

As for antimatter powered orion pusher plates VS antimatter rockets, again I favor the pusher plates because they can put more tons in orbit.

The more tons a space program can put in orbit with ease, the easier space travel becomes period I think. Since then they have more resources to allocate for stuff like reentry and visiting other worlds... all in low Earth orbit or close

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Spaceship We Could Build Now

 

10 hours ago, Spacescifi said:

superheavy half tube maglev

10 hours ago, Spacescifi said:

pusher plate detonations to orbit.

10 hours ago, Spacescifi said:

Elon's starship

10 hours ago, Spacescifi said:

antimatter bombs

Every time when Elon's Starship is getting to the orbit and back, I think:
"Why not add a usual pusher plate to it and launch with any superheavy maglev we have?
It would allow to spend the antimatter instead of just keeping it in our storages like nowadays."

 

55 minutes ago, Spacescifi said:

'best spaceship' means anything that can fulfill the Star Trek mandate

Star Trek. The sciest fi evah!

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15 minutes ago, kerbiloid said:

 

Every time when Elon's Starship is getting to the orbit and back, I think:
"Why not add a usual pusher plate to it and launch with any superheavy maglev we have?
It would allow to spend the antimatter instead of just keeping it in our storages like nowadays."

 

Star Trek. The sciest fi evah!

 

 

My point stil remains.

Space is one place where less is not more, it is only less, and more is always more in space.

Less stuff you can launch at once the less capable your space program is.

Just think.

If we could launch aircraft carrier weighted spacecraft into orbit then we could turn it into an impromtu spacestation in orbit... or we could load it with SSTO shuttles. Or we could load it with propellant and use it as an orbital gas station for spacecraft.

The possibiilities are not endless, but they are many.

Indeed, aircraft carrier weighted spacecraft could even land on the moon since gravity is so weak. Could make a sprawling moon base.

Would not even try doing Earth  reentry with it though, not unless deorbited piecemeal.

Edited by Spacescifi
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There are several problems with launching ultra heavy payloads into orbit.

The bigest issue is that your launch method needs to be extrodinarily energy efficient to avoid major collateral damage from the waste heat alone. External pulsed propulsion like Orion, Minmag, or Epstine-like torchdrives are the only drives capable of lifting such a behemoth and waste a lot of energy, with 50-80% of the energy being wasted in cosine losses alone.

For a 100 kt craft, 50% efficient engine, 8 minute continuous burn of 10 km/s to orbit. 10^16 Joules of energy is needed (equivalent to 2.4 Mt of TNT or 100 hiroshima bombs), half of which is waste heat, with a power of 1.33 PW (100 x primary global energy consumption). Regardless of whether or not such a vehicle launches directly from the surface or not, it will leave a nuclear fireball behind it and likely knock out all electronics on the hemisphere it launches from. It will also probably supercharge the van-allen belts, which isn't a good thing.

This is where Orbital rings excel over any rocket. An orbital ring can only lift a modest 1 kt (only a small freight train) at a time per each of the hundreds of cables connecting it to the ground. As an orbital ring is stationary relative to the surface, and lifting can be done by electric motors, much less energy is needed to get payload to space. A 100 kt payload send to 200 km over 100 trips would only need 10^14 joules , which is a lot less, but still a lot. The real kicker is that less than 5% of the energy would be waste heat, and instead of this energy being released in intentionally uncontained nuclear explosions over a matter a minutes, it would be as friction in the motors which could be dissipated as non-ionizing energy directionally into space over several hours.

This only gets the vehicle into space, and not orbit though. This is where the orbital ring also excels. An orbital ring is well... a ring encompassing the entire planet, this makes it the perfect place to magnetically accelerate a craft in the natural vacuum of space up to orbital or even escape velocities, again with negligible amounts of waste heat that can be safely dissipated. You could even have a series of orbital rings at increasing heights, different inclinations and eccentricities, or around other planets, to receive the craft and send it to its next destination. Orbital rings also have the added bonus of being incredibly good for intraplanetary (earth based) transportation, being able to between any two points on earth in an hour for the price of a train ticket, and unlike starship, could link directly to city centres or rural areas (no supersonic booms, or launch pads, only a train terminal)

The real question is why launch from Earth at all. Even star trek builds their large ships in space, with only shuttles for surface-orbit transportation. In this case, the orbital ring is still superior. Take up the pieces individually (or from the moon) and construct in on the ring itself.

 

As far as interplanetary and interstellar travel, beamed plasma propulsion (like Magbeam) or laser propulsion are the way to go. No on board propellant would be needed to achieve speeds between 10% and 50% of c, several times faster than what bussard fusion ramjets could do if proton-proton chain fusion wasn't a distant pipedream. This is more than fast enough to warrant hyper-responsive point defence systems to track, ionize, and deflect specks of dust hundreds of kilometers ahead of the craft in a matter of milliseconds to avoid becoming a relativistic scrap heap.

The main difference between laser and plasma propulsion is that plasma can provide greater acceleration for less energy, but would need a supply of particles to fling at craft and has a more limited range.

Even the "vast unknowns" of what-would-have-already-been-extensively-studied-by-orbital-mega-telescope-arrays-with-enough-resolution-to-identify-life-and-civilizations-decades-prior-to-any-vessels-arriving-there-space could be accessed, as both methods can be used to brake at distant stars. Beamed laser propulsion requires a light sail on the craft, which can slow the craft down for a stars light pressure. Beamed plasma propulsion requires a plasma sail, which can be used a magnetic brake to stop just about anywhere.

 

All of this can be achieved without any developments in material sciences, fission, or fusion (apart from the sun), and without irradiating half the planet with every launch.

As of yet theoretical developments like gamma-ray lasing, magnetic monopole catalyzed nucleon decay, Q-ball based on demand free matter-antimatter conversion, Q-ball vacuum batteries, and subluminal alcubierre warp drives would be a major game changer. Even more so in the unlikely situation where the universe is broken enough for superluminal travel to actually be possible, and the lack of causality that results from that.

 

Regarding hard scifi propulsion systems, space infrastructure, and future developments, the Orion's Arm Universe ProjectAtomic Rockets, and Isaac Arthur youtube channel are all great places to look into this stuff more.

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I frankly don't see a reason to use the maglev.

I do see lots of reasons not to though.

1. Unless your track is nearly vertical, your gravity turn is going to be messed up, so it needs to go vertical at some point.

2. You can't turn the rocket sharply, both because rockets don't handle side loads especially well without substantial, heavy reinforcement and because massive maglev trains with no jointed sections will derail, high-center, or crash into the rail in a severely upturned track. This means that in order to go from 500 mph horizontally to 500 mph vertically without over a G of sideloading not caused by gravity, your track needs to be something like 5 kilometers tall and wide and 8 kilometers long. And remember, it acts like a giant lever for that side-loading, so you need huge reinforcement structures so it doesn't snap the track off below it. This reinforcement also adds additional wind forces which means you need even more of it to reinforce it against high winds, or this needs to be dug into the side of a mountain. Either way this won't be some spindly flimsy radio mast type structure but a gigantic high speed railway bridge for rockets through half the atmosphere.

3. Starting at 500 mph only saves you a small amount of Delta-V. Same with starting at 500 mph on the end of a giant space bridge. You still have 96% of your speed and 99% of your altitude left to go. That isn't totally irrelevant due to the Oberth effect, but it's not very relevant.

4. It is considerably more complex, slower, and larger than just building a giant cannon. 500 mph takes virtually no effort for a hybrid combustion cannon or light gas gun to do, and even a pure compressed air gun can achieve that velocity if needed, with the added bonus that the rocket and the cannon only take vertical forces from launch. Put the rocket on some kind of disposable or recoverable piston or sabot, or possibly the pusher plate for a nuclear rocket, then accelerate straight upward. You can easily handle more G in this direction too, as much as the rocket would normally generate from launch, so accelerating upward at several G might not be unreasonable. The force on the launch tower is also purely vertical, so no need to design it to withstand more sideloading than the wind will put on it. And in fact, it isn't even being compressed significantly by the rocket or gas but rather it is being pressurized, so your thousands of tonnes monster of a projectile puts literally no vertical weight on barrel as it accelerates. All of the force is being channeled through the compressed gas down to the chamber of the cannon, which can use the ground as structural support, be underground, or even BE the ground.

Now, yes, the cannon does need to deal with wind and it's own weight. If you want it to accelerate slowly and be kilometers high, there are three approaches I can see.

 

1. Put radio mast style cables on it.

2. Make it thick and rigid. But still not as thick as a bridge to space would be.

3. Put the tower inside something that doesn't respond to wind.

 

Structural considerations for giant vertical cannon:

How heavy is 1 meter long of barrel material? This will be proportional to the overpressure of the barrel multiplied by the area of the barrel. So, f.e. a barrel 20 meters wide inside (we're talking about a 20000 mm cannon!) with a peak overpressure of 5 atmospheres and an implied launch force of 16000 tonnes-force (157 MN) would be trying to put 5 MN against each linear meter of wall. We want to withstand much more than that to avoid popping the barrel. How about designing for 10 MN/meter?

Ok, so what are the options for materials?

Well, we want high specific tensile strength, but this thing is also huge, probably will have no issue with its own weight even if it's quite tall, because wind and internal pressure so dominate the forces on it, so we also want low cost per kg. So even though it might be tempting to build it out of millimeters thick of composites, which can reach yield strengths of 2000 MPa and are still less than 2000 kg/m^3, we also need to keep in mind that this comes at the cost of, well, cost.

1 kg of high strength composites might be $30.

1 kg of mild steel could be $0.30. Sure, it's 1/8th the strength and 4x the density, but it's also 100x cheaper. That makes it 3x cheaper as a pressure vessel.

Low alloy steels costing more like $0.50/kg can still easily have 500-1000 MPa of tensile strength. Although at a density of 7800 kg/m^3 their specific strength is less impressive.

Pine wood might also be tempting if you can align the grain since it does have a tensile strength of 60 MPa for a density of just 600 kg/m^3 and a cost of $0.60/kg. It would however be somewhat difficult I think to construct a pine barrel of this size that maintains its tensile properties. Even so, the specific strength to cost ratio is as good as steal.

Aluminium is slightly more expensive but by no means unreasonable at $1.20/kg or so, and has similar specific strength to pine or low alloy steel.

Some quick math says whichever of those you use, the barrel will be about 6 tonnes per meter. That means you need 30000 tonnes for a 5 kilometer barrel. That's about $20-50 million in raw material costs. I wanna emphasize the "raw" part. I don't know what the cost to actually assemble the tube is.

 

Now, keen readers will note that a tube made of metal 12 mm thick, 20 meters across, and 5000 meters tall is not gonna stay up on its own. It will be subject to high winds and buckling forces. It should be perfectly able to avoid pure compressive failure though, as the 8000 cm^2 should more than withstand 300,000,000 N of its own weight by about double.

So, first improvement: we need strong, stiff girders around the whole thing like a radio mast so it doesn't kink inward.

Second improvement: we need large cables like a radio mast to make it withstand high wind speeds and won't buckle or fall over.

 

Now... is it worth doing... probably not. At least not in the form that needs to be kilometers tall and employ slow acceleration. It might be worth making a much shorter, narrower barrel for payloads that can take, say, 1000 G acceleration on launch, and reach much faster launch speeds overall.

 

As for Orion, using it in the atmosphere would work but... the problem is you need to be extremely far from anything sensitive to heat or shock. And then there's another problem. You can't use it in upper atmospheric to low orbit altitudes because of Nuclear EMP and artificial radiation belts, so you need to get your apoapsis to something pretty crazy. Like, several thousand kilometers, to spread the gamma rays out enough not to hurt anything, and you need to do that within 40 km of the ground so you don't spread them out too far. Any detonations at all between 20 and like 1000 km could prove very destructive unless you're somehow preventing gamma rays from impacting the upper atmosphere.

Edited by Pds314
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Current surface pressure maglevs are rather useless for spaceflight, but evacuated vacuum maglevs can reach similar speeds to cannons without worrying about overpressure (though under pressure becomes a problem). StarTram is a good example of how maglev can be effectively used for near term space launches, and Launch loops are a good example of more mid term space launches. 

If you're looking for lightweight support and/or need impossibly strong materials, then active support and/or buoyancy is the way to go.

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On 4/7/2020 at 12:23 AM, Spacescifi said:

My point stil remains.

Space is one place where less is not more, it is only less, and more is always more in space.

Less stuff you can launch at once the less capable your space program is.

The big risk of making bigger rockets is the lack of cost-effective payloads.  If you have lots of large payloads you want to launch into orbit, then it is cheaper, easier, and less cataclysmic to just build a huge rocket to launch it as opposed to a pusher-plate design.

Designing and building a single use chemical rocket with the same orbital payload capacity as your antimatter-pusher-plate will cost less than just manufacturing the antimatter for your pusher-plate design.

When it comes to rockets in general(and chemical rockets in particular) bigger is better.

Tank volume grows with the 3rd power and tank surface only grows with the second power, so the larger the rocket, the higher the payload fraction.  Follow the star-ship model(lots of redundant engines) and bigger also becomes more reliable.

 

The only thing a pusher-plate launch vehicle does better than a chemical launch vehicle of the same payload capacity is to make your origin uninhabitable.  And chemical rockets can be made with greater maximum payload capacity then a pusher-plate using the same materials, because a chemical rocket puts less stress on the materials than a pusher-plate will.

All you need is someone with a mission and the funds to pay for it, and you can launch an air-craft carrier into orbit on a chemical rocket even easier than you could with a pusher-plate.

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1 hour ago, Terwin said:

The only thing a pusher-plate launch vehicle does better than a chemical launch vehicle of the same payload capacity is to make your origin uninhabitable.  And chemical rockets can be made with greater maximum payload capacity then a pusher-plate using the same materials, because a chemical rocket puts less stress on the materials than a pusher-plate will.

I'm having trouble seeing your reasoning for this.

1.) Pusher plate vehicles do not have to use antimatter, and the classic Orion designs would release radioactive fallout of course. But the amount is manageable, indeed the total environmental damage per kg of payload may be less as similar amounts of "fallout" are released to the environment by other industrial processes (such as oil extraction and refinement - which is necessary for kerosene) and no one bats an eye. It seems unlikely that the Earth can even be made uninhabitable even with a fairly decent NPP launch rate over long periods. Maybe, maybe, there will be a higher rate of cancer. But some models seem to suggest mild benefits for the population as a whole (hormesis models), and nonetheless we do far more damage to human lives with much less useful endeavors.

2.) Chemical rockets can not be made with a higher payload capacity than pusher-plate vehicles unless the pulse units are chemical explosives. Nuclear Pulse Propulsion has specific impulses around 10x chemical even in a rather crude design. With more advanced designs it can be 30x chemical if not higher. And since Orion vehicles were intended to use steel... no one in their right mind would build a chemical rocket out of steel. Except the Sea Dragon - a big dumb booster that deliberately sacrifices performance for simplicity and just uses shear size to overcome the performance losses. And its total mass would have been on the order of 18 thousand tonnes and only deliver around 500 tonnes to LEO. Compared to the 4000 ton Orion design which was 4000 tons and capable of putting 1600 tons into LEO assuming a rather crude Orion drive. Or 14.4 times more payload as a percentage of the vehicle mass. An Orion as big as Sea Dragon with the same isp as the 4000 ton Orion would deliver over 7000 tons to LEO.

Pusher plate drives can be made to put reasonable stresses on the vehicle structure, the performance is so huge that you can afford the mass to reinforce the vehicle. That's the point. Instead of "Every Gram Counts" it's "Every Hundred Kilograms Count", maybe "Every Tonne Counts". Higher specific impulse and high thrust is just that good - the Tyranny of the Rocket Equation is an exponential relationship. Double the specific impulse, and the mass ratio falls by the square root. This means if your vehicle needs a mass ratio of 16 to reach a desired Delta-V, then doubling the specific impulse reduces this to 4. So even if the Orion reports are too optimistic, they are not likely to be any worse than nuclear thermal, and can be expected to outperform nuclear thermal by a factor of 2 reasonably. That still outperforms chemical even with the large mass of the pusher plate. 

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Let me just remind that the Orion project was not a dedicated "let's find out how to build a superspaceship" project, but a by-product of tactical nuclear ammo development.

When they studied directed blast nuclear ammo, they predictably came to the idea to push the things with directed nukes rather than break them.
And the obvious thing to push was a heavy spaceship, as it is enough bulky to be enough thick and strong.

The nukes were not "better" or "worse", they were just the projectiles they were working on.

Hundreds of nukes also were absolutely not a problem because everyone was going to arm the armies with numerous tactical nukes.
https://ru.wikipedia.org/wiki/Davy_Crockett
Somewhere even the army structure began getting reorganized for better tactical nuke usage.
https://en.wikipedia.org/wiki/Pentomic

So a thousand more, a thousand less was even not a question to discuss. Just take any amount from the store you need and don't forget to sign in the log.

The military Orion was to be armed with the Casaba cannon using similar nukes, so the ship engine is just a by-product of its weapon.
(Btw, can somebody explain me WHY do they call this Casaba "howitzer"? A howitzer throws things on parabola, while the orbital cannon has definitely nothing common with parabolas, it's like an anti-tank gun with direct hit).

 

Historical background is very important.
Say, alcohol and liquid oxygen are not the best fuel for the rocket, as well as steel tin is not the best for a 10 t rocket hull.
But in the circumstances of V-2 manufacturing they were exactly the most efficient solution.

The same about the Orion.

Edited by kerbiloid
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14 hours ago, Bill Phil said:

I'm having trouble seeing your reasoning for this.

1.) Pusher plate vehicles do not have to use antimatter, and the classic Orion designs would release radioactive fallout of course. But the amount is manageable, indeed the total environmental damage per kg of payload may be less as similar amounts of "fallout" are released to the environment by other industrial processes (such as oil extraction and refinement - which is necessary for kerosene) and no one bats an eye. It seems unlikely that the Earth can even be made uninhabitable even with a fairly decent NPP launch rate over long periods. Maybe, maybe, there will be a higher rate of cancer. But some models seem to suggest mild benefits for the population as a whole (hormesis models), and nonetheless we do far more damage to human lives with much less useful endeavors.

The classic Orion will blow itself up in an atmosphere due to the atmospheric over-pressure wave that can go around the pusher plate and crush critical components, not to mention the atmosphere causing the sheet of metal being sprayed at the pusher plate being disturbed by atmospheric effects.  (the first bomb does not take the Orion super-sonic, so that blast-wave *will* engulf the craft in a fireball and over-pressure wave if in an atmosphere.  The pusher-plate only works as a shadow-shield if there is nothing else around to carry/reflect the wasted nuclear energy)

While a nuclear pusher-plate looks like a great idea for deep space, I am trying to convince @Spacescifi that an antimatter fueled pusher-plate surface-to-orbit design is unneeded, incredibly wasteful, and will probably irradiate your launch site.

14 hours ago, Bill Phil said:

2.) Chemical rockets can not be made with a higher payload capacity than pusher-plate vehicles unless the pulse units are chemical explosives. Nuclear Pulse Propulsion has specific impulses around 10x chemical even in a rather crude design. With more advanced designs it can be 30x chemical if not higher. And since Orion vehicles were intended to use steel... no one in their right mind would build a chemical rocket out of steel. Except the Sea Dragon - a big dumb booster that deliberately sacrifices performance for simplicity and just uses shear size to overcome the performance losses. And its total mass would have been on the order of 18 thousand tonnes and only deliver around 500 tonnes to LEO. Compared to the 4000 ton Orion design which was 4000 tons and capable of putting 1600 tons into LEO assuming a rather crude Orion drive. Or 14.4 times more payload as a percentage of the vehicle mass. An Orion as big as Sea Dragon with the same isp as the 4000 ton Orion would deliver over 7000 tons to LEO.

Chemical Rockets benefit tremendously from increasing the scale of the vessel.  While a chemical rocket will be larger than a pusher-plate design with a similar payload, I am not aware of anything that would prevent a chemical launch vehicle for any payload that could be handled by a pusher-plate design.  And if you are using antimatter for the pusher-plate fuel, Chemical will be cheaper and probably safer.

Rockets need to be large enough for Steel to make sense, see Starship and Super-heavy for rockets finally getting large enough that steel makes sense over aluminum and composites.

Pusher-plate designs use steel because they are large enough for it to make sense, and any chemical rocket made to deliver the same payload to orbit will be large enough to warrant similar materials.

Surface to orbit has lots of issues for Orion, and is well within the capabilities of chemical rockets.  While Orion may be the only option for a rapid transit to Pluto, it is a sub-standard option for reaching orbit, and an expensive calamity waiting to happen when you power it with anti-matter for a surface-launch.

 

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3 minutes ago, Terwin said:

The classic Orion will blow itself up in an atmosphere due to the atmospheric over-pressure wave that can go around the pusher plate and crush critical components, not to mention the atmosphere causing the sheet of metal being sprayed at the pusher plate being disturbed by atmospheric effects.  (the first bomb does not take the Orion super-sonic, so that blast-wave *will* engulf the craft in a fireball and over-pressure wave if in an atmosphere.  The pusher-plate only works as a shadow-shield if there is nothing else around to carry/reflect the wasted nuclear energy)

While a nuclear pusher-plate looks like a great idea for deep space, I am trying to convince @Spacescifi that an antimatter fueled pusher-plate surface-to-orbit design is unneeded, incredibly wasteful, and will probably irradiate your launch site.

 

I've never seen any indication that the classic Orion will blow itself up due to over pressure. 

Not only that but the first explosion was intended to be a smaller chemical explosion to push the vehicle into the air and not a nuclear explosive. The "first bomb" is chemical.

And even if that were the case many proposals called for using chemical boosters to loft the vehicle to a higher altitude where air is much less dense, which completely voids the problem of over-pressure provided sufficient altitude is reached.

Antimatter is more suited for magnetic nozzles - especially since if you've mastered antimatter containment then a magnetic nozzle is likely easy to do.

Quote

Chemical Rockets benefit tremendously from increasing the scale of the vessel.  While a chemical rocket will be larger than a pusher-plate design with a similar payload, I am not aware of anything that would prevent a chemical launch vehicle for any payload that could be handled by a pusher-plate design.  And if you are using antimatter for the pusher-plate fuel, Chemical will be cheaper and probably safer. 

Rockets need to be large enough for Steel to make sense, see Starship and Super-heavy for rockets finally getting large enough that steel makes sense over aluminum and composites. 

Pusher-plate designs use steel because they are large enough for it to make sense, and any chemical rocket made to deliver the same payload to orbit will be large enough to warrant similar materials. 

Surface to orbit has lots of issues for Orion, and is well within the capabilities of chemical rockets.  While Orion may be the only option for a rapid transit to Pluto, it is a sub-standard option for reaching orbit, and an expensive calamity waiting to happen when you power it with anti-matter for a surface-launch.

Chemical rockets do benefit from scale. But so do Orions. In fact, Orion vehicles only get more efficient the bigger they are. Millions of tons becomes easy when you have nuclear bombs pushing your spacecraft.

There are actually quite a few limitations on chemical rockets. Even SLS, a rather sensibly sized rocket compared to Sea Dragon, has issues with hydrostatic pressure. It's too large for the engines. This can be overcome. However, the hydrostatic pressure will eventually increase the hoop stress of the propellant tanks, potentially beyond the yield stress of the materials used. There is a size limit for chemical rockets. And that limit is much lower than the millions of tons that are at least theoretically possible with nuclear pulse. The square cube law means more propellant yes, but it does not mean you don't have to have more structure. Indeed, the structural mass percentage of  the fuel tanks will increase with size past a certain point due to the large hydrostatic pressure and the immense forces involved.

Yes, rockets need to be large for steel to make sense. But eventually the structural mass required increases faster than the benefits of increasing the size. Eventually the rockets start to perform worse. Far worse.

Pusher plate designs use steel because they are less sensitive to weight. Shaving off as much mass as possible isn't the priority. So steel is useful and cheap to use. The classic 4000 ton Orion is roughly similar in mass to the Saturn V - yet it uses steel. This is because nuclear propulsion is that much more powerful.

Orion is explicitly amazingly good at surface to orbit - that's what it's best at. High thrust and specific impulse in the thousands of seconds means huge payloads to orbit. It's actually a somewhat mediocre interplanetary drive - it's just the easiest one to build. Mini-Mag is better, though, and Medusa should perform well too.

Anti-matter is a bad idea period for vehicles - there are almost always better options.

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2 hours ago, Bill Phil said:

I've never seen any indication that the classic Orion will blow itself up due to over pressure. 

Not only that but the first explosion was intended to be a smaller chemical explosion to push the vehicle into the air and not a nuclear explosive. The "first bomb" is chemical.

And even if that were the case many proposals called for using chemical boosters to loft the vehicle to a higher altitude where air is much less dense, which completely voids the problem of over-pressure provided sufficient altitude is reached.

Antimatter is more suited for magnetic nozzles - especially since if you've mastered antimatter containment then a magnetic nozzle is likely easy to do.

Chemical rockets do benefit from scale. But so do Orions. In fact, Orion vehicles only get more efficient the bigger they are. Millions of tons becomes easy when you have nuclear bombs pushing your spacecraft.

There are actually quite a few limitations on chemical rockets. Even SLS, a rather sensibly sized rocket compared to Sea Dragon, has issues with hydrostatic pressure. It's too large for the engines. This can be overcome. However, the hydrostatic pressure will eventually increase the hoop stress of the propellant tanks, potentially beyond the yield stress of the materials used. There is a size limit for chemical rockets. And that limit is much lower than the millions of tons that are at least theoretically possible with nuclear pulse. The square cube law means more propellant yes, but it does not mean you don't have to have more structure. Indeed, the structural mass percentage of  the fuel tanks will increase with size past a certain point due to the large hydrostatic pressure and the immense forces involved.

Yes, rockets need to be large for steel to make sense. But eventually the structural mass required increases faster than the benefits of increasing the size. Eventually the rockets start to perform worse. Far worse.

Pusher plate designs use steel because they are less sensitive to weight. Shaving off as much mass as possible isn't the priority. So steel is useful and cheap to use. The classic 4000 ton Orion is roughly similar in mass to the Saturn V - yet it uses steel. This is because nuclear propulsion is that much more powerful.

Orion is explicitly amazingly good at surface to orbit - that's what it's best at. High thrust and specific impulse in the thousands of seconds means huge payloads to orbit. It's actually a somewhat mediocre interplanetary drive - it's just the easiest one to build. Mini-Mag is better, though, and Medusa should perform well too.

Anti-matter is a bad idea period for vehicles - there are almost always better options.

 

Mini-mag works best in space. In air heat will conduct and probanly damage the magnetic metal lattice nozzle.

So.... based on your and my info, the best ship we could build is... two.

 

An orion launch with a minimag attached for the ride.

Released in orbit, whike if the orion crew wants to land it can detach SpaceX starship, which comes as standatd for orions.

 

Edited by Spacescifi
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20 minutes ago, Spacescifi said:

Mini-mag works best in space. In air heat will conduct and probanly damage the magnetic metal lattice nozzle.

So.... based on your and my info, the best ship we could build is... two.

My concept would be to use chemical rockets to loft the Mini-Mag to a suitable altitude where it can then enter orbit under its own power.

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In terms of surface to orbit applications, nuclear saltwater is probably the best you can get for a self contained launch system. It has better performance than orion (traditional, thermonuclear, or min-mag), operates under continuous thrust (to vastly reduce structural and aerodynamic loads), and would have far simpler plumbing.

Of course vacuum cable maglevs of various sorts (launch loops, orbital rings, startrams, etc) would be far superior options, but it seems non-rocket launch methods don't count for whatever reason.

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1 hour ago, Bill Phil said:

My concept would be to use chemical rockets to loft the Mini-Mag to a suitable altitude where it can then enter orbit under its own power.

 

Yes... but my ideal version of a scifi spaceship can takeoff to orbit and land on an Earth world repeatedly.

 

Based on my accumulated knowledge so far, the best option would be an antimatter thermal saltwater rocket.

Basically have a rocket that is mostly water tank, with some payload and crew space to spare, and a sufficient amount of anti-iron suspended in magnetic fields to add to the water propellant as needed.

Takeoff to orbit. Reentry and land on a beach by the ocean. Get crew to put a big vacuum hose into the water. Suck up enough water to fill your propellant tanks. Launch up to orbit again.

Getting to other worlds fast I already let fiction take care of for plot... I only need real sciencs for launch, orbit, reentry and landing.

Question: Will the rocket exhaust plume be a bluish white flame mixed with steam?

Or will it just be one EPIC steam rocket?

 

Edited by Spacescifi
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27 minutes ago, wafflemoder said:

In terms of surface to orbit applications, nuclear saltwater is probably the best you can get for a self contained launch system. It has better performance than orion (traditional, thermonuclear, or min-mag), operates under continuous thrust (to vastly reduce structural and aerodynamic loads), and would have far simpler plumbing.

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

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

32 minutes ago, wafflemoder said:

Of course vacuum cable maglevs of various sorts (launch loops, orbital rings, startrams, etc) would be far superior options, but it seems non-rocket launch methods don't count for whatever reason.

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

24 minutes ago, Spacescifi said:

Yes... but my ideal version of a scifi spaceship can takeoff to orbit and land on an Earth world repeatedly.

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

Basically two engine systems:

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

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

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

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

Quote

Based on my accumulated knowledge so far, the best option would be an antimatter thermal saltwater rocket.

Basically have a rocket that is mostly water tank, with some payload and crew space to spare, and a sufficient amount of anti-iron suspended in magnetic fields to add to the water propellant as needed. 

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

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

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

 

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