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Project Orion: A discussion of Science and Science Fiction


Spacescifi

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2 hours ago, Spacescifi said:

I see, so any more realistic SSTO will be smaller than any navy ship.

You can build an SSTO at any size if your fictional situation requires it. Up to a point, the square-cube law is going to favor larger and larger vehicles. If we had a financially-compelling reason to launch truly massive payloads into orbit, then Saturn V would look like a bottle rocket. The fact is that we don't have a need to launch really ridiculously big payloads into orbit.

2 hours ago, Spacescifi said:

I think even if we had fusion, heavy lift SSTO's on the scale of project orion would not be practical.

If we had pure-fusion-based energy at a reasonably affordable we could and would build all of our launch vehicles around pure fusion-based energy. If we had a reason to lift massive payloads into orbit we would use fusion for that. If we needed an SSTO spaceplane we would use fusion for that. But even with pure fusion rockets, the utility of staging remains attractive.

2 hours ago, Spacescifi said:

So SSTO's will always be glorified shuttles, designed for shuttling back and forth and little else.

SSTOs have never been glorified shuttles. SSTO designs were based on the theory of reusability. But a TSTO will always be more efficient and more readily reusable than an SSTO using the same engines. 

If you want a science fiction spaceship that can take a small crew to Mars or Jupiter or wherever else and back to Earth without refueling, cool. Write one. Give it pusher plates if necessary. But there's no use case for Project Orion.

Edited by Vanamonde
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If the subject of a thread is not of interest to you, skip it. If someone's posts annoy you, set that person to ignore. But please do not post to complain about questions or mock the person asking. That does no one any good and makes the forum a less pleasant place to visit. 

Some comments removed. 

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Technically, Orion is a kind of perinverted solid-fuel rocket by design.

Just with external energy source, other thhan chemical reactions, and with expendable nozzle.

Spoiler

220px-Orion_pulse_unit.png

The channel has a normal nozzle shape, and the used part of energy is a kinetic energy of hot lightweight beryllium gas, expanding from nozzle.

The expendable combustion chamber is filled with a nuke as an energy source.

The nozzle is filled with solid beryllium (oxide?) which is first a neutron reflector, then the exhaust gas.

The tungsten membrane is just a focusing mediator of energy.  Like a vacuum nozzle extender.

If instead of throwing it back you attach this thing to the pusher plate, it would work like an absolutely normal rocket with beryllium propellant and non-chemical source of energy, like any honest nuke engine.
The pusher plate with pistons would be just a normal mechanical suspension of this engine.
Just in this case you don't need the membrane, but do want a nozzle extender instead. And the engine explodes.

The idea of Orion is to throw back the overheated engine, where it explodes but doesn't damage the ship.

Now try to find a source of energy with energy-to-mass ratio comparable to a nuke. Definitely not a chemical by orders of magnitude.

  

1 hour ago, Gargamel said:

This is like comparing apples and iguanas.
Ones is designed to stay in orbit, permanently.   The other uses air pressure to create lift and carry that heavy load.   

Unexpectedly...

I had a feeling that it's something wrong with apples, as Newton was shocked by one of them, having fallen. Of course, it's strange for orbital fruits.

But who could imagine that iguanas can be cargo balloons. That's why they inflate their necks! Such clever lizards...

Edited by kerbiloid
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2 hours ago, Gargamel said:

No.  
 

There is no realistic size for an Orion SSTO.  Size isn’t the main issue though.   Mass is.     
 

This is like comparing apples and iguanas.    
 

Ones is designed to stay in orbit, permanently.   The other uses air pressure to create lift and carry that heavy load.   
 

Somewhat    

An SSTO is any craft that reaches orbit in a single stage.  Single Stage To Orbit.  It can be a rocket, a plane, or any vessel that doesn’t dump stages.   You could literally take an apple to the summit of Olympus Mons and throw it hard enough to enter orbit.   That apple is now an SSTO.   

If we want to talk spaceplanes (which may or not be SSTO), then we can do that.  We can keep taking about SSTO’s too if you’d like, but I think part of the issue is getting the nomenclature right.   

There is nothing stopping stopping you from making an SSTO that rendezvous with an asteroid, mines it, and returns the ore to a planet or another craft, aside from it being highly inefficient.  All those tanks that used to carry fuel are now dead weight, and that hurts your fuel efficiency, forcing you to carry less ore on the way back.   
 

Is that a realistic proposition? Absolutely not, as it is highly inefficient and unnecessarily complicated.   It is far better to have specialized components of a mission  that do one thing, and do it very well.   
 

So yes, the theoretical best use for an SSTO is some sort of passenger or cargo transport that meets up with an orbital platform of some sort, and then returns for a quick turnaround.   However, SpaceX has shown that it might be easier to get the best of both worlds.     They have a booster platform that can get a sizable payload to space, and then return to launch site for a very quick turn around, which allows the upper stage to be that specialized vessel that is required for the specific task.   
 

Apologies if this sounded a bit heavy handed.   

 

You are kind as are other moderators... I did not feel you were heavy handed.

 

At this point I more or less feel that making up stuff in scifi is necessary unless one wants to make viewers suppose rocketry can do things far better than they actually do and without melting the engine.

 

My current scifi drive in mind may be a bit overpowered, but it gets the job done.

And no it's exhaust is not rocket exhaust, but rather high pressured synthesized light. Normal light is low pressure so it can barelly push anything. Not so with pressor rays.

 

T3: Type 3. Means max acceleration at 3g or less for 3 hours. Other types go all the way up to T9. Most manned vessels use T3's as that is all you need for LEO and beyond.

Missiles: Use T9's but there is a catch. Large vessels carry large generators that allow for the gradual release of acceleration of the drive over time. Missile drive generators are too small for that so instead they use all their drive's stored acceleration in a single pulse. In other words... 9 hours of 9g acceleration is shot out their nozzle in a single pulse. All missiles are two staged, as the T9 missile drive is the the first stage and the second is an ordinany chemical missile with RCS.

Because of drive generator scaling issues, only large vessels and missiles use it.

Small manned shuttlecraft do not use the drive and are something of a bygone era. Big ships just land and take off on their own.

Obviously FTL/ways to shorten interplanetary trips also exist that do not rely on the drive discussed here.

Edited by Spacescifi
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9 minutes ago, Spacescifi said:

And no it's exhaust is not rocket exhaust, but rather high pressured synthesized light.

If it's about Orion, no light playes role here.

Its exhaust is an expanding cloud of beryllium gas, shaped by a normal nozzle, and kept focused by a nozzle extender, like in other rocket engines. Just the extender is a membrane rather than a cone.

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10 minutes ago, kerbiloid said:

If it's about Orion, no light playes role here.

Its exhaust is an expanding cloud of beryllium gas, shaped by a normal nozzle, and kept focused by a nozzle extender, like in other rocket engines. Just the extender is a membrane rather than a cone.

 

Orion has it's merits, but it is hardly ideal for how I wanted to use it as an SSTO.

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2 hours ago, Spacescifi said:

At this point I more or less feel that making up stuff in scifi is necessary unless one wants to make viewers suppose rocketry can do things far better than they actually do and without melting the engine.

Only if you insist on your fictional spacecraft being STABs (Single stage To Anywhere and Back again). If you're willing to accept any or all of multiple stage rockets, on-orbit assembly and refueling, some degree of infrastructure at the landing site,  or use of a mothership and dedicated landers (which may be launched separately and make their own way to the destination to rendezvous with the main crew vehicle), then you can have pretty hard science-fiction journeys to anywhere in the solar system. Examples:

  • Starship:    Two stage to orbit vehicle, both stages reusable.  Upper stage refuels in orbit, flies to and lands on Mars, refuels on the surface, returns to LEO.
  • Saturn boosted Orion:   Multiple stages to orbit, booster stages are discarded. Upper stage flies to Mars, deploys separate landers to get astronauts to the surface and back.
  • Aldrin Cycler.  Main spacecraft in permanent cycler orbit between Earth and Mars. Smaller shuttlecraft used at either end to get crew on and off the Cycler.
  • Original Orion.  Single Stage to Anywhere (but don't expect it to land anywhere). Would probably need dedicated shuttlecraft to land crew on another planet but has the mass budget to cope.

The above have all been seriously studied. One is being built. It's not that hard to come up with plausible mission profiles for anywhere in the Solar System using currently available, or reasonably plausible propulsion. It's extremely hard to come up with one that only involves a single spacecraft. 

Yes they will have long journey times, yes they will have challenges to overcome (prolonged crew exposure to zero gravity, need for radiation shielding (either from background radiation or the ship's engines) etc.  This is hard science fiction. No need to write an engineering treatise on any of those problems but showing that they've at least been considered adds realism to the story. Even if that's a throwaway description of the mothership and her rotating habitation module.

If you don't want the story to be quite that hard, then handwave things a bit but keep the technobabble grounded. Use a 'fusion thruster' for example, without going into the nuts-and-bolts details of how it works. Everyone knows that fusion means lots of energy, so a fusion thruster must be really powerful right? 

As for 'not teaching the viewers that  rocketry can do things far better than they actually do', in the immortal words of one starship medical officer. "You're writing fiction, dammit, not an engineering textbook."

 

 

Edited by KSK
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33 minutes ago, KSK said:

Only if you insist on your fictional spacecraft being STABs (Single stage To Anywhere and Back again). If you're willing to accept any or all of multiple stage rockets, on-orbit assembly and refueling, some degree of infrastructure at the landing site,  or use of a mothership and dedicated landers (which may be launched separately and make their own way to the destination to rendezvous with the main crew vehicle), then you can have pretty hard science-fiction journeys to anywhere in the solar system. Examples:

  • Starship:    Two stage to orbit vehicle, both stages reusable.  Upper stage refuels in orbit, flies to and lands on Mars, refuels on the surface, returns to LEO.
  • Saturn boosted Orion:   Multiple stages to orbit, booster stages are discarded. Upper stage flies to Mars, deploys separate landers to get astronauts to the surface and back.
  • Aldrin Cycler.  Main spacecraft in permanent cycler orbit between Earth and Mars. Smaller shuttlecraft used at either end to get crew on and off the Cycler.
  • Original Orion.  Single Stage to Anywhere (but don't expect it to land anywhere). Would probably need dedicated shuttlecraft to land crew on another planet but has the mass budget to cope.

The above have all been seriously studied. One is being built. It's not that hard to come up with plausible mission profiles for anywhere in the Solar System using currently available, or reasonably plausible propulsion. It's extremely hard to come up with one that only involves a single spacecraft. 

Yes they will have long journey times, yes they will have challenges to overcome (prolonged crew exposure to zero gravity, need for radiation shielding (either from background radiation or the ship's engines) etc.  This is hard science fiction. No need to write an engineering treatise on any of those problems but showing that they've at least been considered adds realism to the story. Even if that's a throwaway description of the mothership and her rotating habitation module.

If you don't want the story to be quite that hard, then handwave things a bit but keep the technobabble grounded. Use a 'fusion thruster' for example, without going into the nuts-and-bolts details of how it works. Everyone knows that fusion means lots of energy, so a fusion thruster must be really powerful right? 

As for 'not teaching the viewers that  rocketry can do things far better than they actually do', in the immortal words of one starship medical officer. "You're writing fiction, dammit, not an engineering textbook."

 

 

 

The problem is that none of those solutions work well for going to unexplored or places lacking infrastructure.

You cannot even do a star trek like setting.

 

The second issue I have is that dedicated manned orbiters will sooner or later need replacement of components. Not designed to land means a fleet of second stage shuttles would be the way to fix problems.

 

But again, this does not really allow the lone ship to warp into a solar system, explore, and warp out on the regular.

 

At best it would all be pre-planned and after every mission they would be forced to either go all the way back to base or a find, mine, and process propellant from  an asteroid, moon, or gas giant.

Which also involves exhausting precious propellant so you had better be sure the fuel source is a good one beforehand.

 

The why of space opera is a big deal... the goal is to transplant the concept of sea exploration to the stars.

 

Real technologies are hardly capable of that without infrastructure in place already.

A sailing ship could go anywhere so long it had food for the crew.

 

Space is far harsher and travel times longer while physics put limits on spinning things up for gravity and getting to places in a more reasonable time on par with sailing ships

 

Therefore making it up is necessary in that case.

Edited by Spacescifi
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They absolutely don't.  If you want a Star Trek like setting, you'll probably need Star Trek like technology. There's a reason it was written into the show after all.

But all the problems you point out can be positives as well, if (as you mentioned in a previous thread) you want a story that shows that space travel is still hard. Needing everything to be pre-planned,  having to obtain propellant for the journey home,  needing to use shuttlecraft to land. These are all  risks and places where things can go wrong, that make that exploration journey hard and dangerous. 

Star Trek (and epic scale space opera in general) is great but it's not the be-all-and-end-all of science fiction either.

Edited by KSK
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8 minutes ago, KSK said:

They absolutely don't.  If you want a Star Trek like setting, you'll probably need Star Trek like technology. There's a reason it was written into the show after all.

But all the problems you point out can be positives as well, if (as you mentioned in a previous thread) you want a story that shows that space travel is still hard. Needing everything to be pre-planned,  having to obtain propellant for the journey home,  needing to use shuttlecraft to land. These are all  risks and places where things can go wrong, that make that exploration journey hard and dangerous. 

Star Trek (and epic scale space opera in general) is great but it's not the be-all-and-end-all of science fiction either.

 

You are absolutely right...  I just have trouble thinking a manned or intelligent life race will really take to the stars in greater numbers without technology that is more fantastic like star trek.

 

I mean really... if we stuck a warp drive on a spaceX starship that could go 1 LY per hour the only people going on that mission would be pros.

 Wjich frankly is not exciting unless they are in danger or hilarious with each other being cooped up for so long.

But they could only go few places if not one anyway because of fuel expense.

 

In other words... in real life, doing the star trek thing requires a proper star fleet... not a single orbiter with shuttles.

You would need an entire fleet of orbiters to allow you to visit several locations with them.

Edited by Spacescifi
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I don’t know - an 8 hour round trip to Alpha Centauri would probably make space interesting to more than just the pros. :)

But yes - spaceflight per se is not terribly interesting. What makes it interesting is the human (or alien - this is sci-fi after all) angle, whether that’s an Apollo style leap into the unknown on bleeding edge but ridiculously primitive for the task at hand, technology, or how society evolves on board a generation ship, or everyone pulling together to rescue a stranded astronaut or whatever.

Likewise for space exploration. Unless you’re seriously into the relevant science, most of the time it’s probably going to be rather dull. Science fiction tends to be about the times when the intrepid explorers find something interesting (and relatable) or set off to investigate something interesting that’s already been found. I’m struggling to think of any examples of stories about the geological and astronomical survey of System 2345b, which consists of a handful of rocky planets, a totally standard asteroid belt and a defiantly ordinary gas giant or two. :)

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18 minutes ago, KSK said:

I don’t know - an 8 hour round trip to Alpha Centauri would probably make space interesting to more than just the pros. :)

But yes - spaceflight per se is not terribly interesting. What makes it interesting is the human (or alien - this is sci-fi after all) angle, whether that’s an Apollo style leap into the unknown on bleeding edge but ridiculously primitive for the task at hand, technology, or how society evolves on board a generation ship, or everyone pulling together to rescue a stranded astronaut or whatever.

Likewise for space exploration. Unless you’re seriously into the relevant science, most of the time it’s probably going to be rather dull. Science fiction tends to be about the times when the intrepid explorers find something interesting (and relatable) or set off to investigate something interesting that’s already been found. I’m struggling to think of any examples of stories about the geological and astronomical survey of System 2345b, which consists of a handful of rocky planets, a totally standard asteroid belt and a defiantly ordinary gas giant or two. :)

 

It can make for great comedy if done right. I read an excerpt from an old TOS star trek book where klingons patrolling a sector with no action actually became excited when they saw an asteroid on sensors... it was so sad it was funny. Meanwhile the Klingon Captain's inner monologue was that it was an 'honor' being out there, since he was actually being sarcastic.

 

When the Enterprise shows up the Klingons are delighted for the break in monotony.

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45 minutes ago, KSK said:

But yes - spaceflight per se is not terribly interesting. What makes it interesting is the human (or alien - this is sci-fi after all) angle, whether that’s an Apollo style leap into the unknown on bleeding edge but ridiculously primitive for the task at hand, technology, or how society evolves on board a generation ship, or everyone pulling together to rescue a stranded astronaut or whatever.

Bringing an alien scene to same actors.

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4 hours ago, Spacescifi said:

You are absolutely right...  I just have trouble thinking a manned or intelligent life race will really take to the stars in greater numbers without technology that is more fantastic like star trek.

Agreed. At a minimum I think some kind of FTL capability will be required, which may not even be physically possible.  Crewed interstellar travel at slower-than-light speeds, at least for 21st century wild type  humans, strikes me as a last desperate option against some kind of overwhelming disaster.

On the other hand, there are some interesting stories out there which deal with STL interstellar travel. One of my favourites is Greg Egan’s Diaspora, in which most of the main characters are sentient software running on molecular scale processors. Journey times are dealt with essentially by slowing down the running speed(?) of that software by arbitrary amounts so that a year of subjective time (from the character’s point of view) is equal to an arbitrary number of objective years.

The technology is just as fantastical of course but it’s a different approach than the Star Trek style FTL spacecraft.

Edited by KSK
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13 hours ago, Gargamel said:

An SSTO is any craft that reaches orbit in a single stage.  Single Stage To Orbit.  It can be a rocket, a plane, or any vessel that doesn’t dump stages.   You could literally take an apple to the summit of Olympus Mons and throw it hard enough to enter orbit.   That apple is now an SSTO.   

This makes SSTO discussions a bit tricky in other threads.  The existing SSTO is not only launched, but crewed (Apollo LEM.  Lunar SSTO only).  Building a chemical SSTO is barely within current tech, although following through with such would simply eliminate any actual cargo.  Landing and reusing a chemical (non-air breathing, Earth based) SSTO is essentially impossible.  Thus the "magic Isp" requirement I pointed out earlier.  Obviously any Orion will go to orbit in a single stage (all of an Orion is needed in space), but it isn't coming back to land on Earth.

The idea of buying a ticket for space as easily as air travel is now (or oceanic travel in the early 20th century) seems to imply SSTO, but that ignores just how tricky SSTO really is.  On the other hand, SCRAMJETs and SABRE  show ways to get the Isp you need.  While going SSTO  effectively means you lose the cargo mass of the mass of the air engines + the fuel tanks through the atmosphere,  I'd expect they'd eventually eat that cargo space and go SSTO (although not necessarily at first).  I can't understand why you ignore proven means of getting "magic" Isp and insist on this pusher plate kludge.

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13 hours ago, Spacescifi said:

Orion has it's merits, but it is hardly ideal for how I wanted to use it as an SSTO.

That is the takeaway, and one you should really take to heart.

Also that the merits of the Orion are extremely few, it is useful for only a very specific use case, and there are vast drawbacks. Literally the best answer to any question that involves Orion outside its original use case is "ditch the Orion and never look back". Any technology required to improve it would also make it obsolete. I think that is, essentially, the synthesis of this whole thread, and the answer to most questions you could formulate about it.

As for SSTOs, you're at the opposite end of the spectrum. Or rather, in a different corner of the triangle. SSTO is, essentially, "magic" technology, and if you want to make it work, you must cut a lot of anchors to reality. It requires handwaving, and lots of it. Within any level of realism you must forget anything about payloads, there won't be any mass to spare for them.

Which brings me to the third corner of the triangle: Realism. You can combine Orion and SSTOs to your heart's content for sci-fi, but it will not hold up to any examination of the cold, hard facts. None whatsoever. Keep it in mind, because you bring the question up a lot. Just, no. It works if you don't care about realism, but it does not combine with hard sci-fi. Again, like improving horseback riding by putting the horse on powered rollerskates. There is no possible way that is a good idea in real life, but it's a good gag for a kids' comic series.

So, in the end you have a triangle: Orion, SSTO, Realism. You get to pick two, but you must forget the third one. MUST. If there is a "but what if ...", chances are, the answer is "Nope" with a big N. Just like the rules for the "Cheap, Strong, Light" triangle in materials science. Any combination of two of those properties is going to be deeply negative for the third.

We clear?

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4 hours ago, Codraroll said:

Again, like improving horseback riding by putting the horse on powered rollerskates.

Can someone  with  a dalle account please prompt  “Project Orion horse on roller skates “?

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On 6/8/2022 at 8:54 AM, wumpus said:

This makes SSTO discussions a bit tricky in other threads.  The existing SSTO is not only launched, but crewed (Apollo LEM.  Lunar SSTO only).  Building a chemical SSTO is barely within current tech, although following through with such would simply eliminate any actual cargo.  Landing and reusing a chemical (non-air breathing, Earth based) SSTO is essentially impossible.  Thus the "magic Isp" requirement I pointed out earlier.  Obviously any Orion will go to orbit in a single stage (all of an Orion is needed in space), but it isn't coming back to land on Earth.

The idea of buying a ticket for space as easily as air travel is now (or oceanic travel in the early 20th century) seems to imply SSTO, but that ignores just how tricky SSTO really is.  On the other hand, SCRAMJETs and SABRE  show ways to get the Isp you need.  While going SSTO  effectively means you lose the cargo mass of the mass of the air engines + the fuel tanks through the atmosphere,  I'd expect they'd eventually eat that cargo space and go SSTO (although not necessarily at first).  I can't understand why you ignore proven means of getting "magic" Isp and insist on this pusher plate kludge.

 

For a setting with heavy lift SSTO's being common I think cheating would be necessary but the type of cheating matters.

I focused on Orion so much because it was effective while not OP. But scifi means to an end that are make believe are all too often very OP especially after I actually think outside the box and use it in ways it was not intended.

 

I think a pure fusion Orion would require a very specific cheat that would also help all rockets.

 

Namely a scifi gravity inhibition field generator.

In a setting where rockets and project Orion vessels could peform as if weightless on Earth.

 

Now I looked up Z-pinch and like other fusion rocket schemes a magnetic nozzle is involved so it is a space only type of propulsion.

 

The merits of Orion are multiple:

1. Can perform well both in atmosphere and space.

2. Much easier to make compared to fusion rocketry.

3. Safer than the NSWR by Zubrin on any given day.

 

So in a scifi setting with gravity canceling tech, project Orion vessels would be stiil be less complex and cheaper than actual fusion rockets I think.

 

The easiest pure fusion rockets to make are pulse rockets based on squeezing small amounts of fusion fuel and detonating it while throwing it rearward with magnetic nozzles. Which as I said do not play well inside atmospheres.

 

So project orion really would fit the classic scifi SSTO role well so long gravity can be canceled.

Edited by Spacescifi
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1. Orion can't perform well in atmosphere at least while not moving faster than the explosion shockwave, i.e. several Machs.

2. Horizontal motion without the aerodynamic lifting force means enormous gravitational losses of energy and delta-V.
A plane flying for ten hours has 350 km/s of gravitational losses which are compensated by air.
A horizontally flying rocket or Orion is a pure loss of energy.
The antigravitational repulsors/suspensors play no role, as they still should spend same energy.

So, in every case a plane is better.

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32 minutes ago, kerbiloid said:

1. Orion can't perform well in atmosphere at least while not moving faster than the explosion shockwave, i.e. several Machs.

2. Horizontal motion without the aerodynamic lifting force means enormous gravitational losses of energy and delta-V.
A plane flying for ten hours has 350 km/s of gravitational losses which are compensated by air.
A horizontally flying rocket or Orion is a pure loss of energy.
The antigravitational repulsors/suspensors play no role, as they still should spend same energy.

So, in every case a plane is better.

 

But what if they did not require the same energy?

 

That is the point of scifi really is it not?

We all know that the sheer amount of energy required to pull of feats in scifi is almost always greater than the ship could pull off without melting.

 

Orion is optimized for both air and space travel, but certainly not a master of either. Just good enough.

Edited by Spacescifi
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2 hours ago, Spacescifi said:

But what if they did not require the same energy?

They don't. The gravity does.

3 600 s * 10 h * 9.81 m/s2 = 353 km/s

Orion is in no degree optimized for air travel. It was designed and computed for the space one, and would be destroyed by the nuke shockwave in air.

The plasma jet, which hits the pusher plate, is moving much faster than the shockwave, because it's caused by lightweight beryllium jet flowing from the charge nozzle.

And the shockwave is in air (mostly nitrogen), so 9 u vs 14..28 u.

So, the jet would hit the pusher plate at any speed, but until the ship is faster than the shockwave, next it will be kicked and pressed by the shockwave.

As the pistons are in intermediate position, the shockwave will crack the pistons, flow into the opened barrel and burst the cannon, and then crush the ship from sides.

As the shockwave is several Mach fast at that distance, the ship should first have a 2 km/s velocity. So, it hardly can fly in air.

Edited by kerbiloid
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3 hours ago, Spacescifi said:

I think a pure fusion Orion would require a very specific cheat that would also help all rockets.

 

Namely a scifi gravity inhibition field generator.

In a setting where rockets and project Orion vessels could peform as if weightless on Earth.

If you have a technology that allows you to literally manipulate gravity at will, why do you need an Orion? Why do you need any kind of rocket at all?

This is again running into the problem in which you try to optimise the Orion design and completely obviate it in the process. 

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4 hours ago, RealKerbal3x said:
8 hours ago, Spacescifi said:

I think a pure fusion Orion would require a very specific cheat that would also help all rockets.

 

Namely a scifi gravity inhibition field generator.

In a setting where rockets and project Orion vessels could peform as if weightless on Earth.

If you have a technology that allows you to literally manipulate gravity at will, why do you need an Orion? Why do you need any kind of rocket at all?

This is again running into the problem in which you try to optimise the Orion design and completely obviate it in the process. 

That's besides the fact that Orion drives will be older than stone tablets when we figure out how to manipulate gravity.

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