[1.3] Orion Drive TD Edition

[g777gun]

@TiktaalikDreaming We all have lives to live so it's understandable.

I know a lot of people are against nuclear propulsion. (For obvious reasons) 

This drive could have been made smaller and easier to launch with modern day rocketry. What annoyed me with a lot the old designs is that they were too big with goals to get to planets saturn or to move a... nuclear battleship 

I am not one in favour of space waste and going nuclear on the orion which is fast/powerful/efficient to me is the best way. 

[TiktaalikDreaming]

5 hours ago, g777gun said:

@TiktaalikDreaming We all have lives to live so it's understandable.

I know a lot of people are against nuclear propulsion. (For obvious reasons) 

This drive could have been made smaller and easier to launch with modern day rocketry. What annoyed me with a lot the old designs is that they were too big with goals to get to planets saturn or to move a... nuclear battleship 

I am not one in favour of space waste and going nuclear on the orion which is fast/powerful/efficient to me is the best way. 

They're big because the engineering of the shock system gets worse and worse as you make them smaller.  And the barest minimum size pusher plate is about 8m, as you need to catch most of the shaped charge, while not being too close to the central fission reaction.  The 10m Orion was very specifically designed as 10m so it could fit on top of a Saturn V first stage.  

When they were developing this, a lot of the engineers and scientists were either ex-bomb makers or still involved in the bomb research.  A major motivation was to take their monster and use it for something peaceful.  But you can't turn off the military bits of brains that easily, and they still needed to try to sell the idea to some government agency.  So you got the various battleship concepts and so on.  And spin offs like the Casaba Howitzer.  The battleship was downright benign compared to the doomsday orion.  That thing was MAD personified.

[damerell]

On 9/29/2018 at 6:26 PM, g777gun said:

This drive could have been made smaller and easier to launch with modern day rocketry. What annoyed me with a lot the old designs is that they were too big with goals to get to planets saturn or to move a... nuclear battleship 

It's not at all clear that the old designs for Orion were "too big". One thing we don't in general know about Orion is exactly how small one can make a thermonuclear bomb; that is a closely guarded secret. However, this determines a minimum efficient mass for an Orion vessel; go under that and you just have to have more mass of shock absorber to avoid squashing the crew into paste, and you might as well just add more vessel instead. (A rare case in aerospace where you have no reason not to make a craft heavier).

The 1950s designs were not "too big" either in that they were sized for their missions. You do need a bigger craft to go to Saturn than to Mars - and with 1950s technology, if you want to do anything more than run the most basic instrument probe when you get there, the craft has to be crewed, and since the crew are going to be on the trip for months, that means a vast mass of life support.

Of course, changes in modern rocketry haven't affected the minimum size at all. Developments in nuclear weapons may have, but we aren't allowed to know about those.

[TiktaalikDreaming]

Well, there's quite a bit of documentation on the Orion pulse units as far as mass etc.  So, with a tungsten "propellant" slug for vapourizing and some radiation channeling and so on, the minimum warhead size seems to be about 141kg.  In the 60s of course, not today, if it's changed.  They very very carefully excluded HOW though.  And when trying to sell to NASA, the pulse units got bigger because they didn't think they'd get the clearance required for NASA to get their mittens on the super small nuke tech.

[damerell]

8 minutes ago, TiktaalikDreaming said:

Well, there's quite a bit of documentation on the Orion pulse units as far as mass etc.

There is, but that only tells us you can make one that small - what we don't know is if you can go smaller, and if so, how much.

IIRC there's also an issue that efficiency is poor with small pulse units - a modest increase in size there might yield a much larger increase in, aha, yield and hence in vessel mass.

[TiktaalikDreaming]

True.  All we really know if that in the 1960s they knew how to make them of size N.  I do suspect (from the people involved and how the pulse units got larger when selling to NASA) that that size was fairly indicative of minimum size at the time.  As to whether that's still the case is left as an exercise for someone with better clearance than me.  And yes, efficiency on the really small units is going to be bad.  You need more and more explosive to compress the smaller and smaller amounts of fissionable material to get density higher.  The "efficiency" with regards to plutonium v number of explosions goes up, but at an expense of every other measurement of efficiency you could come up with.  AKA, bang for buck goes WAY down. 

Also, the Orion (the detailed engineering ones anyway, some of Dyson's mad scribblings about interstellar craft weren't) was all fission.  While the moment you start looking at fusion, there's some well understood systems for electronically adjusting yield.  AKA, you could carry one pulse unit type and just control the yield remotely.  The minimum fusion device is still, um, a bit large afaik.  Not the mass of the unit, but the kick it gives would necessitate a pretty big craft.

[damerell]

I certainly suspect that the actual Project Orion knew the minimum size too, but I don't know for sure (and if either of us did know different, we couldn't talk about it). I think we have both read George Dyson's book; some years ago, when it had just been written, I had the pleasure (at the Festival of Inappropriate Technology in London) of seeing George and Freeman Dyson discuss Project Orion.

Your second paragraph is interesting, but surely you would design the craft to be massive enough so you'd only have to dial down a small fraction of pulse units for very specific circumstances. You'd want to use the maximum yield for most pulse units - or why not just bring a bigger craft?

[TiktaalikDreaming]

4 minutes ago, damerell said:

Your second paragraph is interesting, but surely you would design the craft to be massive enough so you'd only have to dial down a small fraction of pulse units for very specific circumstances. You'd want to use the maximum yield for most pulse units - or why not just bring a bigger craft?

Did you ever use the mod when it was working?

There's a lot of things that aren't obvious until you start to use the sucker.  The first is that you never have enough RCS.  But the second is that maneuvers are tricky when you have to use discrete amounts of deltaV.  Having a few different yields means you can mix and match to get exactly the deltaV required for a transfer or what have you.  If all you have is the biggest yield, then your choice is often overshooting or undershooting.

[g777gun]

9 minutes ago, TiktaalikDreaming said:

Did you ever use the mod when it was working?

There's a lot of things that aren't obvious until you start to use the sucker.  The first is that you never have enough RCS.  But the second is that maneuvers are tricky when you have to use discrete amounts of deltaV.  Having a few different yields means you can mix and match to get exactly the deltaV required for a transfer or what have you.  If all you have is the biggest yield, then your choice is often overshooting or undershooting.

My fix for this would be as (I used another space game) to use rockets for maneuvering and fine tuning. Then you wont need other sizes of nukes. However the nukes would have to be the right amount not to overdo the crew. I really think a smaller version is possible nowadays but we will never know. 

[damerell]

I've used both your mod and Roverdude's mod. I think we are talking at cross purposes here. I certainly agree that the ability to dial down bombs would be useful, saving having to bring a vast armoury of carefully selected charges; all I meant was you'd still have a minimum vessel mass, because you'd plan to do all the major dV stuff using your pulse units to maximum capacity.

[HebaruSan]

1 hour ago, TiktaalikDreaming said:

But the second is that maneuvers are tricky when you have to use discrete amounts of deltaV.

What about detonating the same size charges farther from the plate?

[TiktaalikDreaming]

42 minutes ago, HebaruSan said:

What about detonating the same size charges farther from the plate?

Well, in 1967 I don't think they had the electronics to make that as trivial as it would be today.  Plus the cone of gaseous propellant would start to pass the pusher plate, because I'm pretty sure you can't adjust the cone angle.  That said, that would mostly be a feature aiding tuning, so long as you could ensure it wouldn't unduly affect the rest of the craft (which should be shadowed by the pusher plate).  

The only engineering issue I can think of is how it effects resonance on the suspension system.  But the rather fancy active "spring" system they were aiming for could likely be tuned to deal with that.

2 hours ago, g777gun said:

My fix for this would be as (I used another space game) to use rockets for maneuvering and fine tuning. Then you wont need other sizes of nukes. However the nukes would have to be the right amount not to overdo the crew. I really think a smaller version is possible nowadays but we will never know. 

To be honest, looking at the physics involved, I doubt they've achieved a lot more in fission shrinkage since.  I would solidly believe lots of gains in fusion.  But fission criticality is fairly well studied, and compressing metals to achieve that has limits.  Yes, there's some marginal gains to be had in control systems and in slightly better high explosives, but those gains would be pretty small.  There's a possible gain in making the devices more efficient at being propellant, but I don't think there'd be a lot of gain in minimum size.  That said, there could be gains in producing lower yield devices with the same sort of size that would make it possible to make smaller craft.  Keeping in mind that sea level bursts have about ten times the propulsive effect of vacuum bursts.  So, if the craft is lofted to 100km or so, the pulse unit that would have torn the craft apart at sea level, would be about right.

[TiktaalikDreaming]

1 hour ago, damerell said:

I've used both your mod and Roverdude's mod. I think we are talking at cross purposes here. I certainly agree that the ability to dial down bombs would be useful, saving having to bring a vast armoury of carefully selected charges; all I meant was you'd still have a minimum vessel mass, because you'd plan to do all the major dV stuff using your pulse units to maximum capacity.

Agreed.  I thought you meant you could get by with just one pulse unit strength. 

Maneuvers are max until you get to less than max difference in delta V.  I've messed around with various rocket assist, including some fairly serious RCS.  And, the craft absolutely need that for anything resembling docking (for obvious reasons).  But it is nice to have variable yield.  esp if you're using a version that takes into account atmospheric effects.

but yes, there's always a minimum vessel mass so your crew don't end up as kerbal paste.

[g777gun]

by William-Black


Well I have came up with some ideas like making certain parts being able to change about. Rather just keep the Orion part in orbit and just carry on some nuclear fuels.What I like about the Orion is that the trip is short in comparison to real life planned mars missions where you will have to stay on mars for like 4 years before coming home. 

 

[GrandProtectorDark]

1 hour ago, g777gun said:

 real life planned mars missions where you will have to stay on mars for like 4 years before coming home. 

 

To nitpick that. Last time I read myself into planned missions to mars. After arriving in mars orbit, it would be 3-4 months for an optimal Hohmann transfer window for back to earth to occur. A transfer would take 9 months and Orion would get this done faster theoretically, so there's that.

[TiktaalikDreaming]

For years is somewhat pessimistic considering the orbits. Maybe for the best possible transfers. But acceptable transfers happen a lot more regularly. But yeah, the amount of transfer optimisation needed depends heavily on how much delta v you have up your sleeve. And Orion drives have big sleeves

[g777gun]

1 hour ago, TiktaalikDreaming said:

For years is somewhat pessimistic considering the orbits. Maybe for the best possible transfers. But acceptable transfers happen a lot more regularly. But yeah, the amount of transfer optimisation needed depends heavily on how much delta v you have up your sleeve. And Orion drives have big sleeves

Maybe people know things differently to me compared to 10 years ago. What is the theoretical fastest from mars and back? One of the best engines that Nasa had was Vasimr and thing I did not like. By the time you got to mars and landed there is a huge chance it would take too long to get back. Thus most of the ideas I have seen just plan to stay on mars for 4 years. Which sounds very impractical. Some have even said that once their spacecraft get there they cant come back.

[damerell]

 

17 hours ago, g777gun said:

Well I have came up with some ideas like making certain parts being able to change about. Rather just keep the Orion part in orbit and just carry on some nuclear fuels.

I'm not sure what the point of the picture you have is. Yes, a 20 man Jupiter mission is much larger than an 8 man Mars mission, but it's not needlessly oversized; it just must carry more crew, more supplies for each crewmember, and more dV (and these are multiplicative effects on the total mission size).

Leaving the Orion drive in orbit is an astonishingly bad idea from the point of view of making a smaller spacecraft. The Orion drive is ideally suited for landing and takeoff because of its good power to mass ratio, and of course you've got it there already and just need some extra pulse units, whereas a bunch of conventional aerospace would just be additional mass for the rest of the journey.

(Some projected Orion missions did have chemical landers, but that was either because of concerns about nuking the surface of Mars or because a small instrument package was to be landed somewhere and not returned, rather than the entire crew+supplies landing somewhere and returning.)

14 hours ago, g777gun said:

By the time you got to mars and landed there is a huge chance it would take too long to get back. Thus most of the ideas I have seen just plan to stay on mars for 4 years. Which sounds very impractical. Some have even said that once their spacecraft get there they cant come back.

There isn't a "chance" it would take too long to get back - transfer windows are predictable. It's just that you might have to wait a long time for an opportunity to start the mission from Earth. As Tiktaalik says, if you've got an incredible amount of dV, there are many more "windows" and so you have a much wider choice of times to launch the mission.

You do have to wait 4 years on Mars for an optimal return transfer... but if you aren't bringing 4 years' supplies, you may be able to make do with a non-optimal return transfer. I doubt "most of the ideas" you have seen suggest a 4 year wait; it's just that that optimal figure is well known and does tend to get mentioned.

The one-way missions are proposed not because the wait time is long or because there's a chance of having to wait a long time but because landing a spacecraft capable of returning humans from Mars (and having it work) might be too hard, full stop - much harder even than landing a lifetime of supplies.

[TiktaalikDreaming]

On 10/4/2018 at 11:51 PM, damerell said:

Leaving the Orion drive in orbit is an astonishingly bad idea from the point of view of making a smaller spacecraft. The Orion drive is ideally suited for landing and takeoff because of its good power to mass ratio, and of course you've got it there already and just need some extra pulse units, whereas a bunch of conventional aerospace would just be additional mass for the rest of the journey.

(Some projected Orion missions did have chemical landers, but that was either because of concerns about nuking the surface of Mars or because a small instrument package was to be landed somewhere and not returned, rather than the entire crew+supplies landing somewhere and returning.)

The only time you can use an Orion for landing is when there's no atmosphere.  And the final coming to rest needs to be using something else (aka chemical rockets) anyway.

Problem 1: Airburst fireballs.  While the Orion is designed to deal with a blast from a nuke hitting the pusher plate, if you end up travelling through the resulting fireball, then it's not just the pusher plate exposed to the damage.  Now, the fireball is much cooler than the initial burst, but it's still well past the sort of thing you want to fly through.  So, no decelerating in an atmosphere.  For a while I tried to model this using the code, if anyone remembers the Orion mod making everything run REALLY slowly.    When you're accelerating, it's not an issue, so long as you're moving away from the explosion point relative to the atmosphere.

Problem 2: Landing legs.  You need legs that will extend past the pusher plate and protect it.  You might think, "hey, the pusher plate can withstand a nuke, surely you could land on it" but it can only survive a nuke while in pretty pristine condition, while smeared with an ablative oil coating, etc etc.  You land that sucker on it, and you're going to have bad times when taking off.  And, of course, if you have the plate flush with the ground, you can't take off anyway.  Now, once you have these really long legs deployed, if you use the orion drive, you'll cease to have functioning legs very quickly.

Problem 3: Control with discrete pulse units.  It's pretty hard work landing with crappy throttle response, and it'll be even harder using nuclear pulse units.  Not impossible, but I've tried, and I think the chances of getting it right are slim enough you really don't want to try relying on it.

[g777gun]

Just now, TiktaalikDreaming said:

The only time you can use an Orion for landing is when there's no atmosphere.  And the final coming to rest needs to be using something else (aka chemical rockets) anyway.

Problem 1: Airburst fireballs.  While the Orion is designed to deal with a blast from a nuke hitting the pusher plate, if you end up travelling through the resulting fireball, then it's not just the pusher plate exposed to the damage.  Now, the fireball is much cooler than the initial burst, but it's still well past the sort of thing you want to fly through.  So, no decelerating in an atmosphere.  For a while I tried to model this using the code, if anyone remembers the Orion mod making everything run REALLY slowly.    When you're accelerating, it's not an issue, so long as you're moving away from the explosion point relative to the atmosphere.

Problem 2: Landing legs.  You need legs that will extend past the pusher plate and protect it.  You might think, "hey, the pusher plate can withstand a nuke, surely you could land on it" but it can only survive a nuke while in pretty pristine condition, while smeared with an ablative oil coating, etc etc.  You land that sucker on it, and you're going to have bad times when taking off.  And, of course, if you have the plate flush with the ground, you can't take off anyway.  Now, once you have these really long legs deployed, if you use the orion drive, you'll cease to have functioning legs very quickly.

Problem 3: Control with discrete pulse units.  It's pretty hard work landing with crappy throttle response, and it'll be even harder using nuclear pulse units.  Not impossible, but I've tried, and I think the chances of getting it right are slim enough you really don't want to try relying on it.

I would never land the Orion. There is no point. I mean one could make the argument to repair it but if its already in space then chances are you are screwed. Orion is too delicate to be taking chances at landing, if the plate becomes damaged you better hope you can get people from earth to come repair it, as long as you are in earth orbit. 

(I use chances a lot cos nothing ever goes 100% perfect, as history shows.)

Orion has the amount of power needed to carry along backup escape rocket vessels and it can carry a large 'Apollo style luna lander' for landing on mars.

The only thing the Orion would do in my book is act like the ferry, that's all. This is why I really want this mod. 

And besides. I wouldnt to irradiate the landing site. Don't care if the pulse units have low radioactive fallout  (mainly being airburst) figures I just wouldn't do it. 

Please fix this mod if you have time.

Also computers nowadays would make the Orion much easier to work with being able to calculate ejection safe distances and wireless activation of the bombs. One may think.

[damerell]

On 10/5/2018 at 11:20 PM, TiktaalikDreaming said:

The only time you can use an Orion for landing is when there's no atmosphere.

Most of the bodies it's practical to land on have no atmosphere anyway. You're obviously not going to land anything on Venus and, equally obviously, there's nothing to land on on the gas giants. Mars is very much the odd one out here and from Project Orion p. 185 there was a proposal to descend on Orion to within a few thousand feet of the surface of Mars (I suspect the nuclear airburst issue is less bad than one might think because our spaceship can be much more robustly constructed than normal, and the original researchers clearly thought it could be overcome) and finish the descent on chemical rockets. The only issue mentioned is the fallout (aha) from nuking the surface of Mars.

I don't think you need enormously long landing legs; you just have them extend slightly past the pusher plate at the last minute (we'd better land an uncrewed probe first to find a nice hard spot) and you'd then dig a great big hole before takeoff. It's certainly tricky to time the last pulses if one is eyeballing it in KSP, but I'll bet even with 50s computing you can have the last one go off at just the right time... assuming the effective yield of bombs is very tightly controlled and the effects from a near-ground detonation are known, of course, which I admit is nontrivial.

I wonder if it is practical to design the ablative plate with a series of thin slices on the base? Then perhaps we can ditch any slices that are damaged in landing to produce a pristine surface.

On 10/6/2018 at 12:04 AM, g777gun said:

 Orion is too delicate to be taking chances at landing

Tiktaalik is quite right above that it is more delicate than one might naively suppose an enormous steel plate is, but it is still vastly less delicate than any other system you might be using for landing.

[SlamduncAZ]

I’ve recently been looking for a good Nuclear Pulse Propulsion mod.

Does this mod allow for off-world ISRU/production of nuclear magazines?

[TiktaalikDreaming]

23 minutes ago, SlamduncAZ said:

I’ve recently been looking for a good Nuclear Pulse Propulsion mod.

Does this mod allow for off-world ISRU/production of nuclear magazines?

There's no provision for it, and the minimum setup would be quite a thing to build off world. The mod also hasn't been compatible since 1.3

 

[FreeThinker]

On 5/1/2019 at 5:01 AM, TiktaalikDreaming said:

There's no provision for it, and the minimum setup would be quite a thing to build off world. The mod also hasn't been compatible since 1.3

 

Last work on it appears to be 2 years ago. Any plans to make it work again?

Edited May 2, 2019 by FreeThinker

[TiktaalikDreaming]

16 minutes ago, FreeThinker said:

Last work on it appears to be 2 years ago. Any plans to make it work again?

I have plans. But the original extends part, not part module, and that's not supported anymore. I started looking at that when the links to change masses changed, and for me there a lot of work converting.