Project Orion: A discussion of Science and Science Fiction

[KSK]

Crew Dragon takes about 40 minutes to return to Earth from starting its deorbit burn. 

https://blogs.nasa.gov/spacestation/2020/08/02/the-spacex-crew-dragon-is-go-for-deorbit-burn/

Twelve minutes of that is taken up with the actual burn because it’s carried out using small maneuvering thrusters. 

The Shuttle (which is probably a better comparison vehicle here) took about an hour from starting the deorbit burn to landing. Six hours was the total time including closing the payload bay doors, getting the crew suited up and other checks and procedures.

[JoeSchmuckatelli]

From what I understand about ST - they didn't so much orbit the planets they visited (at least not ballistically) - they were in a 'parking orbit' which was essentially a stellar orbit co-located with the planet. 

Clearly they had the drive power to resist being drawn down to the surface while maintaining a stable altitude /distance. 

If you presume that technology - is there any issue with just 'driving ' down and back?  ST shuttles never looked ballistically capable to me - so clearly they were not entering the atmosphere at ballistic speeds. 

... 

@Spacescifi- with this in mind: from your scenario I presume that handwavium isn't applicable... But given the power of the ship you propose: why even enter orbit around the planet?  (Doing so requires attaining orbital velocity relative to the surface / atmosphere - along with the concurrent risk of overheating during entry).

Wouldn't it be better to set an intercept course with the planet on approach and just decelerate until you touch down?  (the relative velocity of the ship and the world in relation to the star has to be zeroed out anyway... Why not make landing part of that equation?) 

[RCgothic]

I don't think spacecraft in Star Trek generally "orbit" as such. They effectively use anti-grav tech to hover in place. Shuttle craft between the mothership and the surface therefore don't have to scrub off the excess velocity, they just have to ascend.

My reasoning for this is that ships are usually depicted as loitering over a surface position despite being shown as relatively close to the planet, and shuttlecraft aren't generally shown as scrubbing off realistic re-entry energies.

That said, Star Trek ships at sublight are also generally described as acheiving significant fractions of the speed of light with their non-neutonian impulse drives and what would be 10s of thousands of Gs of acceleration. Even if they did orbit at appropriate velocities, it would be a matter of seconds to shed that velocity and enter the atmosphere with a relatively benign propulsive descent.

[KSK]

Star Trek vessels do go into orbit but the technical details are handwaved away or deliberately ignored for dramatic effect.

From Memory Alpha:

According to the Star Trek Encyclopedia (2nd ed., p. 460):

The term "standard orbit" was used as an ingenious means of allowing the captain to give a technical-sounding command when the ship entered orbit, without having to bore the viewer with tedious details of orbital inclination, apogee, perigee, and orbital period. It was at one point thought that standard orbit would be synchronous, allowing the ship to remain stationary over a single point on a planet's surface, but a visual-effects shot of the ship, motionless over the planet, would not have been dynamic, thereby lacking dramatic value. Moving the ship was, therefore, a conscious decision by the show's producers. Even when the ship was required to "hover," some slight movement was shown so that the image wouldn't be static.

The Star Trek Encyclopedia – A Reference Guide to the Future is the "definitive" Star Trek reference book, compiled by the production staff and officially licensed and endorsed by Paramount Pictures/CBS Consumer Products.

So the Star Trek Encyclopedia is about as canon as it gets. 

 

Edited March 28, 2022 by KSK

[wumpus]

2 hours ago, JoeSchmuckatelli said:

From what I understand about ST - they didn't so much orbit the planets they visited (at least not ballistically) - they were in a 'parking orbit' which was essentially a stellar orbit co-located with the planet. 

Note that "parking orbit" was a phrase used in the Apollo program, although I don't know if it had escaped into the public by 1966 (the show was canceled 1969).  Saturn rockets put the Apollo command module in a low (very low) orbit so they could do some quick "go/no go" checks in a single orbit and then use the Oberth effect to go to the Moon.  It wouldn't be a useful term when bringing a 24th century starship to a planet you wanted to be "nearby" a landing party.

I'd have to assume that the Enterprise could kill all delta-v needed to rendezvous with a planet (trivial next to flying between stars), fly perpendicular to the atmosphere if they pleased at a fairly high mach number (ships built out of unobtanium hold together much better than plastic models of the original ship), and land arbitrarily fast.  Or more likely, just have the enterprise use anti-grav tech (or just 1g thrusters) to hold position and have shuttlecraft land on the planet (same way, kill orbital velocity and straight down.  No "reentry" needed).

Allegedly, models for shuttlecraft were made for the original series, but were never paid for and thus never used.  The transporters were quickly "invented" as a much cheaper and quicker means to show crew members on the planets.

[JoeSchmuckatelli]

9 minutes ago, wumpus said:

Allegedly, models for shuttlecraft were made for the original series, but were never paid for and thus never used

Au contraire, mon frere

 

[kerbiloid]

Spoiler

https://ru-m-wikipedia-org.translate.goog/wiki/БАЗ-5921?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=ru

https://en.wikipedia.org/wiki/OTR-21_Tochka

Edited March 28, 2022 by kerbiloid

[JoeSchmuckatelli]

Way ahead of her time.  Wheels are anachronistic?

[Gargamel]

Why make a reference to Star Trek, but then negate it by changing the ship to something completely unlike Star Trek?   The physics/realities of Star Trek are their own special kind, as mentioned, we can't completely change the rules of the game, then expect to play by the original rules.  

[kerbiloid]

2 hours ago, JoeSchmuckatelli said:

Wheels are anachronistic?

The historical prototype. To be replaced with anti-grav repulsors.

[DeadJohn]

Any landing from space needs to balance the hull "strength" (heat tolerance, not getting ripped apart by aerodynamic forces, stress from rapid pressure changes, magical inertia dampeners so the crew doesn't get pulped by deceleration) with fuel capacity. Our current technology is constrained by both hull strength and fuel. Reentry uses minimal fuel, just enough for the hull to survive the process.

If your hull is supremely strong, you can decelerate more than current spacecraft to get a sharper reentry, slam hard into the lower atmosphere to rapidly lose speed from drag, and land.

If your fuel capacity is near infinite like with Star Trek, you can decelerate a lot while still in space, effectively matching the surface speed of the rotating Earth beneath you, then just fall downwards. This takes much more fuel but bleeds off most horizontal speed before reentry. This would also be relatively fast, minutes not hours, and the vertical fall wouldn't generate much heat.

[RCgothic]

Although "much more" is still comparatively little when you have mass-altering ability combined with fusion thrusters (impulse engines)

[StrandedonEarth]

As far as ST orbit-to-surface-to-orbit ops go, the transporters were "invented" because a traditional landing would cost too much in special effects.

Easier and cheaper to just handwave some transporter effects ...

[wumpus]

19 hours ago, DeadJohn said:

Any landing from space needs to balance the hull "strength" (heat tolerance, not getting ripped apart by aerodynamic forces, stress from rapid pressure changes, magical inertia dampeners so the crew doesn't get pulped by deceleration) with fuel capacity. Our current technology is constrained by both hull strength and fuel. Reentry uses minimal fuel, just enough for the hull to survive the process.

If your hull is supremely strong, you can decelerate more than current spacecraft to get a sharper reentry, slam hard into the lower atmosphere to rapidly lose speed from drag, and land.

If your fuel capacity is near infinite like with Star Trek, you can decelerate a lot while still in space, effectively matching the surface speed of the rotating Earth beneath you, then just fall downwards. This takes much more fuel but bleeds off most horizontal speed before reentry. This would also be relatively fast, minutes not hours, and the vertical fall wouldn't generate much heat.

And here's the issue with the whole thread.  21st (and 20th) century spacecraft design always considers mass first because of the rocket equation and always try to at least minimize delta-v.  But 24th century engineers don't care because they have dilithium crystals and other unimaginable tech.  We are like 18th century shipcraft enthusiasts sitting around a coffeehouse wondering how much sail a 21st century ship could take and how that would effect cross oceanic travel.  Time becomes the limitation, and it looks nothing like anything NASA would ever consider (or even someone who built those little Enterprise NCC-1701 (no bloody A, B, C...) models that always broke).

It also shows that mapping out the real requirements doesn't make sense in fiction.  The only reason people care about the engines while flying is that propellers are seen as "the cheap stuff", slow, and likely don't have all the other budgets as the big boys.  But jets aren't "jet engines" and haven't been for quite some time.  They are [high] bypass turbofans.  But that doesn't matter at all to the people with the tickets (and unlikely to even the pilots, but they were certainly taught that at some point).

[StrandedonEarth]

3 minutes ago, wumpus said:

Enterprise NCC-1701 (no bloody A, B, C...) 

Hey Scotty, when did you join the forums? Get sent back in time again?

Fun fact: the original Enterprise model concept was upside down (saucer low), until Roddenberry thought it looked much better flipped over

[KSK]

1 hour ago, StrandedonEarth said:

Hey Scotty, when did you join the forums? Get sent back in time again?

Fun fact: the original Enterprise model concept was upside down (saucer low), until Roddenberry thought it looked much better flipped over

Give the guy a break - he's probably talking to his mouse again.   And yeah, I'm with Roddenberry on that one. Can't quite picture the Enterprise flipped saucer low.

2 hours ago, wumpus said:

It also shows that mapping out the real requirements doesn't make sense in fiction.  The only reason people care about the engines while flying is that propellers are seen as "the cheap stuff", slow, and likely don't have all the other budgets as the big boys.  But jets aren't "jet engines" and haven't been for quite some time.  They are [high] bypass turbofans.  But that doesn't matter at all to the people with the tickets (and unlikely to even the pilots, but they were certainly taught that at some point).

Sort of agree, depending on the fiction.  I'm right with you on not spelling out the details because your characters most likely won't know or care about them and I'm not a great fan of Star Trek Technical Manual style explanations based on piling technobabble atop technobabble.  If I was writing a near-future space travel tale though, I would probably want to figure out roughly what a given engine was capable of for the sake of keeping things consistent behind the scenes, even if I just called it a 'fusion thruster' or something in-story. Plus, it's helpful to know how roughly how much of a fictional spaceship needs to be devoted to propellant tanks, when it comes to describing them.

Edited March 29, 2022 by KSK

[Spacescifi]

On 3/28/2022 at 10:46 AM, Gargamel said:

Why make a reference to Star Trek, but then negate it by changing the ship to something completely unlike Star Trek?   The physics/realities of Star Trek are their own special kind, as mentioned, we can't completely change the rules of the game, then expect to play by the original rules.  

 

It was an 'experiment' to see what would really happen IRL.

Nothing in IRL is infinite, at least no mass is, but massless things at least appear to be so (time and space).

I do not like infinite with 'experiments'. It's like cheating im KSP.

 

21 hours ago, KSK said:

Give the guy a break - he's probably talking to his mouse again.   And yeah, I'm with Roddenberry on that one. Can't quite picture the Enterprise flipped saucer low.

Sort of agree, depending on the fiction.  I'm right with you on not spelling out the details because your characters most likely won't know or care about them and I'm not a great fan of Star Trek Technical Manual style explanations based on piling technobabble atop technobabble.  If I was writing a near-future space travel tale though, I would probably want to figure out roughly what a given engine was capable of for the sake of keeping things consistent behind the scenes, even if I just called it a 'fusion thruster' or something in-story. Plus, it's helpful to know how roughly how much of a fictional spaceship needs to be devoted to propellant tanks, when it comes to describing them.

 

Exactly so. When it comes to fictional spaceships it is hard to make them capable without making them overpowered.

 

On the one hand you want near infinite 1g acceleration for manned flight and gravity.... even though the same abiity would inevitably create missiles with the same ability that would make space opera as we know it obsolete.

 

If you do not want overpowered thrust or delta v you must limit both. And to not be completly arbitrary about it I finally figured out a way.

 

Single Constant Impulse drive: Linked to main rocket engine and requires it. Thrust and acceleration are based on the last main engine burn.. only difference is that once you initiate the SCI drive you accelerate at that rate constantly without rocket engine input.

 

How? Spaceship splits in two and chases the other half while attracting and repelling it.

 

Edited March 30, 2022 by Spacescifi

[JoeSchmuckatelli]

52 minutes ago, Spacescifi said:

SCI drive you accelerate at that rate constantly without rocket engine input

Continued acceleration?  So past the speed of light, eventually?

[KSK]

2 hours ago, Spacescifi said:

Exactly so. When it comes to fictional spaceships it is hard to make them capable without making them overpowered.

On the one hand you want near infinite 1g acceleration for manned flight and gravity.... even though the same abiity would inevitably create missiles with the same ability that would make space opera as we know it obsolete.

If you do not want overpowered thrust or delta v you must limit both. And to not be completly arbitrary about it I finally figured out a way.

Single Constant Impulse drive: Linked to main rocket engine and requires it. Thrust and acceleration are based on the last main engine burn.. only difference is that once you initiate the SCI drive you accelerate at that rate constantly without rocket engine input.

How? Spaceship splits in two and chases the other half while attracting and repelling it.

Ahh - I think you either misunderstood me  or I wasn't very clear.  When I'm thinking near future, I'm thinking non-FTL ships powered by something that's recognizably a rocket engine. It may be chemical, it may be some variety of nuclear thermal, it might be fusion at a pinch (pun not intended). Either way, I'll be scouring the depths of Project Rho, looking for engine designs that have at least been worked out to some extent and come with actual values for thrust and specific impulse - although I'll probably assume that my fictional engines are operating at the upper end of any performance ranges described.

I probably won't be going into the details of how - for example - a solid core nuclear thermal rocket works and I'll almost certainly never give actual numbers for engine performance but I will have them to hand. So, if the story calls for a journey to Planet X, I'll plan it out in broad strokes: pick a likely sounding total delta-V for the journey and from that, work backwards to figure out how much fuel I need. In turn, that gives me a rough idea of what the spacecraft looks like and what sort of capabilities it might have. Is this basically a flying fuel tank on a one way journey? Does it need to be capable of aerobraking? Are the engines efficient enough that I have spare cargo capacity for a orbit-to-surface shuttle? Can I go for a bigger design with a built in centrifuge, or are my crew just going to have to deal with zero-g for the journey? That sort of thing.

More fictional spaceships are actually fairly easy to make capable without being overpowered. The problems tend to come in if you insist on using acceleration to create artificial gravity.  If you're okay with assuming some kind of artificial gravity generator (which, to my mind is no more outlandish than your SCI drive), then the need for a constant 1g acceleration drive disappears. Alternatively, if you're okay with a hyperdrive, then you can effectively do point to point interstellar travel with almost arbitrarily short journey times. Healthwise, it doesn't much matter if your crew are in zero-g for a few hours, or even a couple of days.  Heck - you could go for a biological solution and assume that your crew is genetically engineered to overcome the effects of living in zero-g. Or just accept that the effects of zero-g can't be fully mitigated and have a setting where some planets are simply off-limits to certain space-faring characters because their gravity is too strong.

There's a reason that some technologies (like artificial gravity) have become sci-fi tropes. They solve a particular problem without going too far down the rabbit hole of unintended consequences.  If you want the story to involve a futuristic technology (rather than the technology just being Trek-like background stuff that makes things happen), then a good way of doing it - in my opinion at least - is pick some limitations and follow the consequences of those limitations, rather than tying yourself in epicycles trying to solve every last problem. And don't explain the technology - any 'explanation' is likely to be technobabble at best, and leave you open to those pesky unintended consequences at worst. 

For example, in The Mote in God's Eye, spacecraft have a shield (I forget what it's called but it's named after an in-universe character). If I remember rightly it's basically a perfect energy absorber - right up to the point where it overloads and releases all the stored up energy in one go. Which tends to be bad news for whatever it's shielding.  So you can fly through the upper atmosphere of a star and be absolutely fine - but you'd better make sure not to stay in there too long, and you probably want to plan for a few days downtime afterwards whilst your shield radiates all the stored up energy away. The physics of how this shield works are never explained (for good reason) but its basic operational principles  are clear and come with meaningful consequences. 

 

Edited March 30, 2022 by KSK

[KSK]

A couple of other thoughts.

Firstly - I was being kind of prescriptive in that last post, for which I apologize.

If you (and that's generic you rather than addressing this to Spacescifi) want to delve into the minutia of a fictional technology, trying to figure out a plausible way to make it work and keeping everything tight and consistent within the story setting, then go for it! I'd be the first to tip my hat to you if it works, and concede that you're a far better worldbuilder than me, with a damn sight more patience.

Secondly - and this is directed to Spacescifi - you might get more informative answers to a straight question rather than dressing it up in a particular sci-fi setting.  If you're looking for a design for a reusable orbit-to-dirt rocket powered shuttle, I'm sure there are folks on here who would help crunch the numbers and give you some idea of how fictional, or otherwise, the thing would need to be. 

[Spacescifi]

7 hours ago, Spacescifi said:

 

It was an 'experiment' to see what would really happen IRL.

Nothing in IRL is infinite, at least no mass is, but massless things at least appear to be so (time and space).

I do not like infinite with 'experiments'. It's like cheating im KSP.

 

 

Exactly so. When it comes to fictional spaceships it is hard to make them capable without making them overpowered.

 

On the one hand you want near infinite 1g acceleration for manned flight and gravity.... even though the same abiity would inevitably create missiles with the same ability that would make space opera as we know it obsolete.

 

If you do not want overpowered thrust or delta v you must limit both. And to not be completly arbitrary about it I finally figured out a way.

 

Single Constant Impulse drive: Linked to main rocket engine and requires it. Thrust and acceleration are based on the last main engine burn.. only difference is that once you initiate the SCI drive you accelerate at that rate constantly without rocket engine input.

 

How? Spaceship splits in two and chases the other half while attracting and repelling it.

 

 

7 hours ago, JoeSchmuckatelli said:

Continued acceleration?  So past the speed of light, eventually?

 

On second thought I won't use that after all. And this is BEFORE I even read the follow up posts. For one I don't like the look, and the look is a BIG part of what matters to me besides how it works.

 

It turns out that the OP design for this post would work just fine with a bit of tweaking. See... I LOVE the look of the project orion spaceship, and adding a cross cylinder beam to the front just looks even more awesome to me.... because it is actually a practical feature. If the ship ever decides to deorbit via reentry it can simply fly headfirst, since the 'hammerhead' will take the heat instead of the pistons and pusher plate, which you really do not want getting messed up anyway.

Getting up and down I already mentioned how... even though both require first stages, whether via a  booster or scifi tractor beam lifting platforms.

Shuttlecraft would be seaplanes with pusher plates, since pure fusion bombing the land, while less fallout than a nuke, is still not a healthy for anyone nearby. So pure fusion bombing the ocean would be a much better trade off I say.

The space for the landing engines would be on the underbellies of nacelles on the flanks of the rear end, and also on the underbellies of the 'hammerhead' at at the opposing ends.

But realistically taking off a planet for the main ship would be an emergency maneuver, not standard. As it should be.

 

The awesome thing about pusher plate propulsion is it scales up better than it scales down, even with pure fusion bombs, which means making dart swarm missiles out of them would be impossible anyway.

 

Which further tips the scale into classic scifi space opera... which is more or less what I want with a dash of realism.

 

But you are right, I also figure out that constant acceleration for gravity is wholly unnecessary if I just bite the bullet and accept scifi artificial gravity.

 

Of course, given that it is me doing it, I cannot simply make it just work like REAL 1g. In my case it would be 'attractor tiles', metallic tiles that attract anything that weighs 100 kilograms or more with 1g.... so long as you are touching it.

Which would mean as soon as you jump off you are weightless... which would make for some fun sports in zero g to say the least! It also means you cannot really drop anything and a lot of of stuff would still float around... best of both worlds I guess.

As for pure fusion pulse propulsion, not only do I like it for how it looks, but also because it uses the power of the processes of the very environment it is in.... star nuclear fusion.

Using the power of the stars to travel among the stars! Very fitting. Since on earth chemical processes dominant, but in space radiation, gravity, and stellar nuclear fusion processes dominate.

 

And of course the simplicity and multi-functional use is also appealing. Not only can you SSTO with it (granted for emergencies or for seaplane SSTO shuttles only) but you can travel around the solar system too!

 

And yes... FTL or hyperdrive right now is about as valid scifi artificial gravity without spinning, so I agree with you. Some tropes just beg to be used if you do not want to overpower the setting.

[StrandedonEarth]

1 hour ago, Spacescifi said:

Of course, given that it is me doing it, I cannot simply make it just work like REAL 1g. In my case it would be 'attractor tiles', metallic tiles that attract anything that weighs 100 kilograms or more with 1g.... so long as you are touching it.

Which would mean as soon as you jump off you are weightless... which would make for some fun sports in zero g to say the least! It also means you cannot really drop anything and a lot of of stuff would still float around... best of both worlds I guess.

100kg? Well, it won’t affect anyone in my family, although it should work on Schmuckatelli. But worse, it won’t help your plumbing function at all. And floating stuff can actually be hazardous in many ways. 

[JoeSchmuckatelli]

9 minutes ago, StrandedonEarth said:

it should work on Schmuckatelli

I'm just big boned.

[Spacescifi]

3 hours ago, StrandedonEarth said:

100kg? Well, it won’t affect anyone in my family, although it should work on Schmuckatelli. But worse, it won’t help your plumbing function at all. And floating stuff can actually be hazardous in many ways. 

 

I goofed (did not realize 100 kilograms equals 220 pounds).

I will change it to 70 kilograms or above in weight.

So some would be okay.... I would at least.

 

Sorry kids.... you don't weugh 154 pounds? No gravity for you.

And lady.... I know you're skinny, so either bulk up by working out OR start packing on some fat. Those are your options. Sorry!

 

So either chubby, giant, or muscular ladies need apply lol.

https://ihaventshavedinsixweeks.com/2015/05/28/what-154lbs-looks-like-on-different-womens-bodies/

 

Well... you can buy 50 kilogram attractor tiles (110 pounds or more will be ok), but those are more expensive.

 

100 kilogram attractor tiles are cheap, 70 kilogram are moderately priced, and the 50 kilogram ones are expensive and seen on luxury spaceliners.

 

So if you weigh a lot you can boldly go where no man has gone before on the cheap!

 

Edited March 31, 2022 by Spacescifi

[Gargamel]

5 hours ago, JoeSchmuckatelli said:

I'm just big boned.

And undertall. 

2 hours ago, Spacescifi said:

Sorry kids.... you don't weugh 154 pounds? No gravity for you

I would safely wager money on the fact that a significant minority, if not a small majority of people who have been to space would be floating around.   
 

But then.... what about 65 kg of water in a (remarkably heavy) 5kg tank?   How does the gravity tell it’s working on one thing not two. What if they drink some water?   
 

This is what we keep saying.    Arbitrarily devised details in fiction create paradoxes in logic that destroy any suspension of disbelief.