NASA concept for a nuclear pulse spacecraft. A nuclear pellet is fired from the aft end of the craft and detonated, yielding far more thrust than conventional chemical rockets.
Last week I had mentioned the upcoming Ron Moore pilot “Virtuality”, set to air on June 26th, just a few short weeks away. That thread lead to a spirited discussion as to what might be the propulsion system of the show’s spacecraft, the Phaeton, a NASA style interstellar craft. In fact the Phaeton uses nuclear pulse propulsion, and I’ve asked my good friend Mike if he would explain how it works. Mr. Okuda has seen the Phaeton and witnessed the ship’s propulsion system in action, and he is delighted to elaborate on it for us. Take it away Mike…
Zefram Cochrane notwithstanding, most fans know that real scientists have very little idea how faster-than-light “warp drive” or “hyperdrive,” could actually work, or even if they’re possible. A lot of slower-than-light technologies seen in stories and films for reaching the stars are more grounded in scientific reality, like lightsails, ramscoops, and generation ships. Unfortunately, most of them involve extremely long travel times, miniscule payloads, or near-magical breakthroughs in engineering. (Sometimes all three!) Present-day rockets are amazing machines, but they have only a tiny fraction of the performance that would be needed to travel to the stars on anything approaching a human timescale.
Nuclear pulse propulsion was a real concept that was developed in the late 1950s and early 1960s. It would have used nuclear bombs as propellant. At the back of the spacecraft would have been a large, flat “pusher plate,” mounted on a series of beefy shock absorbers. There’d be a small hole in the middle of the pusher plate, through which a series of small nuclear bombs would be ejected. Each bomb would explode, pushing the ship forward. A typical ship design would require some 800 small nuclear charges to be detonated in rapid succession in order to boost a ship into orbit. Additional charges could have sent it to the Moon, the planets, or even further. The power of this proposed system would have been amazing. They figured they could launch spaceships weighing many hundreds – even thousands – of tons much more easily than using NASA’s chemical rockets.
This early test for the Orion Project demonstrated that the concept was a viable one. This test was powered by a charge of C-4 explosives.
The US Government’s Advanced Projects Research Administration (ARPA) was responsible for this Top Secret project, which was code-named Orion. Project leaders included numerous heavy-hitting veterans of the Manhattan Project, including physicist Freeman Dyson, of “Dyson sphere” fame. The Orion project lasted about six years, during which they conducted a lot of design work and engineering studies. They even conducted an amazing proof-of-concept test using a small model powered by one-pound charges of C4 explosives. They also built a test object that withstood a direct nuclear blast at Bikini Atoll, demonstrating that the pusher plate could survive. The Orion team believed they could land a manned expedition on Mars by 1964, and they expected to send a mission to the moons of Saturn by 1970. No kidding! Star flight would take considerably longer, but some concepts show travel times of just a few decades to nearby stars.
(NASA has a present-day space project with the same name. Today’s Project Orion is building a cool spaceship called a “crew exploration vehicle.” It will replace the space shuttle, providing a safer way for astronauts to reach the International Space Station. Orion ships will return humans to the Moon, and will eventually take us to Mars and beyond. But here I’m talking about something entirely different.)
There were, of course, very serious questions of the tremendous environmental damage that nuclear bombs would cause to our atmosphere and our magnetosphere, especially since “clean” bombs proved to be more difficult to develop than had been hoped. (One partial solution might have been to launch an nuclear pulse ship using conventional chemical rockets, only using the nuclear pulse drive in orbit.) There were very real political issues, and of course, there were fears of what might happen if any of the propulsive charges were to fall into the wrong hands. By 1963, the Nuclear Test Ban treaty led to the cancellation of the project. But if humanity ever needs to get really big ships into space – for example, if and when we have to deflect a big incoming asteroid – Project Orion could very well save the human race. (Carl Sagan suggested that a nuclear pulse spaceship could be an excellent use for the Earth’s stockpiles of nuclear weapons.) But unless such an emergency arises, the environmental damage from nuclear pulse launch means that using it would probably be a spectacularly bad idea. The only problem for me is that it is just such a cool concept that I really would love to see it. The good news is that help is on the way.
I hope I’m not getting anyone in trouble by mentioning that Doug let slip the fact that the spaceship Phaeton in Virtuality uses nuclear pulse propulsion. (Hopefully, not in Earth’s atmosphere!) I have to say that I’m really looking forward to seeing this amazing concept on the screen, especially since it’s being done by Gary Hutzel, plus Doug and their team of visual effects geniuses.
Here is an 8-minute talk by George Dyson (son of physicist Freeman Dyson), talking about the top-secret Project Orion, which would have utilized this system
Here’s an amazing clip. It’s from a BBC documentary made in 2003. It includes film that shows tests of the Orion concept using small charges of high explosives.
Here’s a rendering of what a nuclear pulse powered expedition to Mars might have looked like:
Thank you Mike! Outstanding as usual!
Holy cow I was just listening to the WSJ this morning and they were discussing space travel by way of an ion drive. Sounded like a good idea at the time, but now with this invention we could kill two birds with one stone…get rid of the nukes and help propel us to other planets.
great stuff Doug and Mike, I love techy stuff in action!
interesting photo shown…
i knew about ORION for years… but i never saw those top photos of the “bell”
interesting- in current years the “bell” shaped -acorn- shaped craft has become a new UFO meme, going back to supposed NAZI tests and the infamous Kecksburg PA UFO crash story.. 1965 i think..
that first photo would be a perfect stand in for a scifi channle like UFO hype show like the one on keckburg done with bryant Gumbal a few years ago… the scale, shape and design is the closet thing ive ever seen to an actual flying object, that matches the eye witness desciptions of the “acorn” in the woods in 1965.
i wonder if orion project offers some solid evidence to put the acorn ufo stories into reality and to rest as “vulcan landings”
were any launches done… that could have deposited a capsule in PA in 65? when i was 13 and into trek and starlog, i also read all the blue book/ and bigfoot stuff too…. it all meshes… though age and wisdom have eroded my beleif in the UFO /occult/xcreature/stuff.:)
but thats a flying acorn if i ever saw one..godnamit!
lol
Great stuff. I’ve seen the TED presentation before and the last clip as well. I’ve always been fascinated by Orion but doubt we would ever see anything based on it in real life.
I think they talked about using nuclear propulsion for aircraft for a while, too, though it used a completely different principle. They even came up with a fairly decent concept model for a gas turbine powered by a heat exchange between cool air and hot water from the reactor (to solve the problem of radioactive exhaust), but the environmental impact of a crash caused them to drop the idea. I wonder if such an idea might not work in space, though the volume the fuel would take up (liquid oxygen, heavy water, coolant, etc) would still be as much of a problem as conventional rockets, unless of course they could come up with a better way of using the heat generated by the reactor to drive the ship.
as I recall, they also experimented with nuclear powered rockets that directed the thermal energy of a reactor out the engine to provide thrust, or something like that. A “nuclear wessel” if you will.
Of course, if you want to see the Orion concept in action in popular culture, look no further than the 1998 file Deep Impact… the spaceship used to deal with the asteroid threat was powered by an Orion drive.
Ack… the 1998 FILM Deep Impact. Stupid fat-fingered typing!
Orion-type propulsion should at least look interesting on screen, and it would work nicely for a solar system explorer, but no way will it get you to another star. There’s not enough plutonium on the planet to make enough nuclear devices to accelerate a ship to any appreciable fraction of c. A more plausible nuclear engine would be the electron beam or laser-detonated deuterium pellet system imagined for the BIS Daedalus. Even there, I believe the ship (an unmanned probe) was only designed to get up to 0.1c in a flyby past Barnard’s Star 6 ly away (Ford, is there any tea on this spaceship?). Even if you don’t use exotic stuff like antimatter or Bussard ramscoops, you can maybe combine a deuterium rocket with a bank of ion drives juiced by MHD. I see from IMDB that Kevin Grazier from JPL was a science advisor; I’d be curious to see what he thought of all this. I suspect that a very good authority might have been found in Dr. Marc Millis; Marc know his propulsion schemes backwards and forwards (and is a big Trek fan).
Project Orion! Very cool!!!
This is really awesome. I knew that nuclear spacecraft propulsion had been proposed, but I never knew that some of it suggested ejecting and detonating bombs for propulsion.
Virtuality sounds awesome.
A manned mission like the one suggested in the BBC drama-documentary about the “Grand Tour” might used pulse detonation propulsion as it’s my understanding is that current Ion drive technology doesn’t provide that much thrust.
I remember a test device sent to the Moon that would take several months to get there using its Ion engine.
I’m with Rick — I can’t swallow the notion of a nuclear pulse drive achieving the near-lightspeed velocity implied in Virtuality‘s premise of a “10-year” journey to Epsilon Eridani, which is 10.5 light-years away. If it were, say, a 20-year journey to Alpha Centauri, that might be close enough to swallow, though still a stretch. Don’t get me wrong, it’s nice that they’re trying for something more credible than the usual FTL handwave, but it’s only relatively more credible. They could’ve stood to do more research.
I’m also wondering how they’ll pronounce “Eridani.” It’s supposed to be stressed on the second syllable, “Eh-ridden-ee,” but when I’ve heard it spoken onscreen it’s usually “Air-ih-donny.”
People involved with the design were aware of this. I think Rick knows well the arena. Hopefully it will be somewhat enjoyable anyway.
To Barrie: The advantage of ion drive is that it takes a lot longer to use up the fuel, so you can keep accelerating much longer. On a short journey, it takes longer than a conventional blast-hard-and-coast rocket, but for a longer trip, an ion rocket would probably take less time since it could keep getting steadily faster and faster over time, eventually adding up to a higher average velocity than the conventional rocket. Also ion drives are more efficient, making them preferable for longer trips even if they do take more time.
On the link http://goodshipphaeton.wordpress.com/2009/06/09/mike-okuda-and-the-physics-of-virtuality/ it’s said that the Phaeton uses matter/antimatter weapons technology to propel the ship.
Any thoughts?
Antimatter bombs could give you considerably more kick than nuclear — I think that fusion is about 7% mass-to-energy conversion and M/AM is 100%, though a lot of that energy is in the form of neutrinos and thus isn’t really usable. Still, you’d need insanely huge amounts of antimatter to make this kind of drive work. With current technology, it would take millions of years to manufacture enough of the stuff. Most antimatter propulsion proposals involve using tiny amounts of antimatter to catalyze or intensify nuclear reactions.
io9 has a gallery of concept art from Virtuality:
http://io9.com/photogallery/thephaeton/
It looks like a very plausibly designed ship, although I think the artist on that “Phaeton physics” diagram got the gravity vector wrong on the rotating modules. Still, the design in the first two images, which I assume is final, looks very credible.
The sketches are in the neighborhood. If you liked those you will really like the finished ship. IMHO it’s a beauty. Gary and Richard Livingston, our illustrator, have come up with something very memorable.
Oh boy! Ohboyohboyoh boy! I am a huge fan of the Orion program and my interest in this new show just went through the roof on little nuclear explosions! Thanks for the updates, guys!
Rick, I know that name “Marc Millis” … didn’t he run a website for NASA, “Warp Drive When?” and do work for the Advanced Propulsion Laboratory? The first time I stumbled across that web site, I had a cold chill go down my spine because it almost made the fantastic drives seen in Star Trek sound plausible.
A friend just reminded me of Clarke’s second law -
“When a distinguished but elderly scientist says something is possible, he’s very probably right. When a distinguished but elderly scientist says something is impossible, he’s very probably wrong.”
I remember Richard Hoagland writing about ORION and its British cousin DAEDULUS in the 70s for an SF mag. I think they could get up to 40% of lightspeed if they didn’tr try to slow down, for a flyby of Barnard’s Star that wouldn’t take long to arrive there.
The speed for in-system travel were phenomenal. I’m remembering back 35 years or so, but I think it was 100 men and a 1000 tons of supplies to Mars in three weeks (including slowing down to orbit) or 50 men and 100 tons to Pluto in a month (including slowing down.)
Those are serious Major Matt Mason speeds … as in, the universe I wanted to grow up in.
I heard of some of those concepts a few years ago. What I always found and still find amusing is the “solution to everything” approach in the 1950/1960 when it came to nuclear power. Of course, being born in 1976 I do remember Tschernobyl/Chernobyl quite good. But, as stated earlier, I always wondered if scientists really thought about using those propulsion methods within the planets atmosphere.
Cheers
Thorsten
Psion – You’re exactly right. I don’t believe Marc’s site is still around (i’ll check; haven’t talked to him in a long while), but I’m sure there are ways to access archives of the pages. All of the different propulsion schemes Marc and others talk about result in specific types and amounts of exhaust products and energy imparted to a spacecraft, and there are methods for calculating how much structure/consumables you’re going to need per crew person per unit time, how much propellant you’ll need to get to a particular destination, etc. It goes on and on, but we can make pretty good guesses, at least for applying to an entertainment product.
I perused the sketches posted on io9, and while there are some interesting engineering solutions to the vehicle, I had to giggle a bit over the hab rotation rate. I realize these may only be back of the envelope type of calcs, but some of the spin rates and distances from the center would cause people to throw up if they turned their heads the wrong way.
Even the centrifuge in 2001 (not to mention Mission to Mars) would do the same thing, so a little suspension of disbelief -is- sometimes needed, though I thought Mission to Mars just plain sucked.
There -are- ways to design plausible spacecraft in film and television; not everybody in the entertainment field can do it or can see if an offered design will pass muster. But it’s a wonderful thing when it works.
Good point, Rick. But it would be equally true of the Discovery in 2001 and the Leonov in 2010, wouldn’t it? This centrifuge actually looks considerably bigger than those, so it’s not as bad.
According to The High Frontier, people could handle a rotation rate of 1 RPM without difficulty, but more people would begin having difficulty as the rate increases. However, it says some people can adapt to as much as 10 RPM. So the 4 RPM indicated on the revised sketch would be difficult for a lot of people — I’m sure I could never handle it — but perhaps the members of the Phaeton crew were specifically chosen for their ability to acclimate to it. Or maybe there’s some kind of medical treatment or inner-ear implant available in their time that can compensate.
Christopher – The Leonov would have had the same problem, yep. On the other hand, the L5-type habitats, with 1g, would have to be around 1000 feet in radius and would result in about 1.7 revs per minute. Some of the space med folks I’ve talk with say you could probably be okay with Mars-type gravity, about .35g, for a long interplanetary trip (don’t know about interstellar; didn’t ask). You’d still need about a 300′ radius and maybe 1.5 revs to get Mars g. Gravity gradient is still going to be a bitch for smallish-looking ships like the Phaeton appears to be. In the vehicles I illustrated for Science Digest, the diameter of main hulls (other than the Forward laser sail) was about 300 feet, so a centrifuge section inside was possible, though things like the Enzmann and Bussard vehicles were under thrust most of the time. With a ginormous deuterium supply for the Enzmann, and the ramscoop running on the Bussard. It’ll be interesting to see how the Phaeton slows down; I’m pretty certain it can avoid running into it’s own bomb exhaust.
Not meaning to be a total wet blanket, but I don’t see a forward scatter-shield. Anything you run into at relativistic velocities is going to cause a nasty lethal cascade of secondary particles. The BIS Daedalus has a front shield, as well as a projected smoke cloud, and the Bussard has a giant-sized stack of multilayer plates:
http://www.ricksternbach.com/buss.jpg
Notice the shield is the same diameter as the ship. Now Bussard never did quite work out how to protect the crew after flip-over, but he did gloss over some slightly complicated hinged mechanisms to move some layers to the back.
I know that mag fields are being discussed for some of this, though I believe that’s mainly for solar system slowboat trips to ward off solar/cosmic radiation. Fun stuff.
Rick said – “…though I thought Mission to Mars just plain sucked. Glad to know I’m not the only one! It happened to be on TV the other day and I decided to give it a go again. Nope. Still just as bad as the first time.
I remember hearing about this project Orion a while back. It’s a shame that political pressure and fear lead to the cancellation of this project. Were the fears unfounded? Probably not, but think of where we would be had the project been allowed to continue. Mankind started treating disease with leaches. Then we grew in our knowledge and understanding of that thing and today we have surgery being performed by robots. My dad is a CRNA and the hospital he works for just sent him and some co-workers down to Texas to see some of the advances in this area.
I feel if we had been allowed to develop this technology, just as we have made advances in medicine, there would have been advances to making this a safe technology. As Chris and Rick have pointed out, it wouldn’t have gotten us light speed, but imagine how much closer we would be to understanding how to achieve that concept?
Can’t wait to see how it’s used in Virtuality! Perhaps science fiction will again turn the wheels of advancement!
Rick and Mike
You guys offered soem great insight on how this stuff might work.
I am going to take soem of Gene Roddenberry’s optomism about the future and say that warp speeds and hyoper light travel is possible…we just haven’t figured it out yet.
Thanks for your thoughts on the subject.
I studied the Orion Project as part of my Space Studies degree. It’s a fine concept, but there are some things that make it unfeasable. Rick touched on one, being a limited payload. Meaning you can only carry so much munitions. And if there happens to be an accident where you lose the entire payload, you’re in deep trouble.
A second major concern is the radiation from the explosions themselves. It’s a double-edged sword. You need to carry a large ammount of shielding to protect the crew, the equipment, and the supplies. Which with current technology, makes it too heavy.
And the explosions themselves cause wear and tear. In which in space and far from home, you’re not going to have replacement parts available.
Of course with Hollywood, you can easily go around a lot of this.
ScottD – “Of course with Hollywood, you can easily go around a lot of this.”
For sure. A fellow SF artist friend from way back, Derek Carter, once drew a cartoon of him and me in the cockpit of a giant angular oddball float-y spaceship with no visible engines, and his word balloon said “Rick, if this spaceship were real, it couldn’t do half the things it can do now!”
So yeah, I get it. Always have. But I will always push to have things make -sense- within their particular context. If James Lipton ever asked me what thing I hate, it would be sitting through a couple of hours of images and sound that couldn’t stand up to any sort of reasonable questions. Never give up, never surrender.
Wait a second…if these guys are supposed to be going interstellar, and their trip takes ten years (ship time?), how many years pass on Earth? I have to break out the tau factor calc again. They might be lucky if they can squirt one episode of their reality show out every few months, by the ground clocks. Their great-grand-kids might be around to see the season finale.
Unless, of course, it isn’t a real trip to e eri, but an incredible simulation.
“…with this invention we could kill two birds with one stone…”
Actually, we could kill a lot of birds, with Orion intended to niclearly blast off from the surface to orbit, atomic fallout and all
The thing is, it seems that would be the best system available to lift great masses to orbit, short of an Space Elevator.
My name might be mud here because this show might not be worth all the interest.
But I hope it’s good. I will usually watch most things scifi on TV and will relunctantly give up on them. I give them a shot though.
About Orion, I have a hard time believing the promises of the technology. There’s a difference between something in theory and something in practice. Look at the difficults developing the fairly conventional rockets NASA is working on now. You can come up with a great idea but when you get down to the nitty gritty details, some things fall apart. But I’m mostly a “do everything” kind of guy. So I’d love for an Orion propulsed design to actually be worked on. And I also recognize that I’m the kind of guy that would have had serious doubts about TV. “Oh, I bet you could get a recognizable picture…but no way will it ever look comparable to film.” Heh.
Phaeton is supposed to travel yo Epsilon Eridani system in 10 years. That means that it has to travel almost to light speed. That is impossible with this nuclear pulse propulsion, it would be impossible even with a fusion reactor. It will need a matter-antimatter reactor to reach such speeds. And ofcourse it is impossible to construct so many nuclear bombs to send the ship all the way to epsilon eridani (10ly from earth).
Who said we can’t build enough bombs?
If I am not wrong, the Deep Impact movie’s spaceship was supposed to use a mini-Orion-style main engine. It had a small pusher plate behind. So one can design a cool Orion-type ship
, even if an interstellar variant would need to be gigantic.
Messiah spaceship production model pics: http://smg.photobucket.com/albums/v102/McTodd69/Deep%20Impact%20Messiah/
(A small quicktime montage of Deep Impact VFX featuring the ship and other things here: http://www.vfxhq.com/zmovies/deepimpact.mov
Its parent article: http://www.vfxhq.com/1998/deepimpact.html )
S*it Doug! I knew the US had 10,000 nukes, but that really puts into a VERY scary perspective. Also, let’s not forget that here in the UK our government has decided to spend upwards of 6 billion pounds upgrading Trident nuclear subs and their arsenals.
Can you imagine what NASA could do with $17 billion a year? Man, we’d be on Mars already!
Makes you sick, doesn’t it!
Rick, good point about the varying thrust (post 25). The Phaeton design seems to be using a concept I thought of myself some years ago: modules that rotate so they can adust to both centrifugal acceleration and rocket thrust, so there’s a consistent “down” vector for the crew. In my idea, the modules were bottom-heavy so they’d automatically rotate to fit the resultant vector from the combination of thrust and rotation. These diagrams suggest that maybe the Phaeton stops rotating prior to firing the engines, so it’s either one or the other. Still, it’s a cool idea.
Point taken about the radiation shield too. Maybe at the time of the pilot, they haven’t deployed it yet because they aren’t going fast enough?
And you’re right about the relativistic time lag being a damper on the success of the reality show. How loyal an audience could it have if the episodes came out so infrequently? Another reason I wish the target star were Alpha Centauri instead — you could get away with a lower tau factor.
Christopher – “Maybe at the time of the pilot, they haven’t deployed it yet because they aren’t going fast enough?”
Heh. Don’t count on it. Some of the techy notes point to a radiation shelter inside a hab module based suspiciously on the Bigelow inflatable, which is fine for solar system travel. But the shield for relativistic stuff is a brute thing on the front that not only protects people, but keeps the entire structure behind it from falling apart due to neutron embrittlement, mechanical abrasion, etc. because what’s coming at you is like the worst high-pressure particle hose imaginable. But then I’m sure you knew that.
I suspect that whoever put this thing together assumed that one design will work no matter what the regime.
Hey Rick, what of the radiation shield from the nuclear explosives used for propulsion? I think there is a greater threat by than cosmic and solar radiation.
And yes, the Bigelow Inflatables are good for orbiting and perhaps travel to Mars, but not interstellar travel. And I don’t see it being an effective radiation shelter unless their is a 1 foot thick layer of water between the hull and the crew. (Water is remarkably good at radiation filtering).
Rick Sternbach -”If James Lipton ever asked me what thing I hate, it would be sitting through a couple of hours of images and sound that couldn’t stand up to any sort of reasonable questions. Never give up, never surrender.”
You sound like me when talking about JJ’s recent contributions…
I guess writers can always fall upon the EPR Paradox to justify a design? The strongest argument, I am told, is the effect of lens flare on quantum spin. That’s just what I heard, anyway. :-]
We clearly need to design a perfectly rigid body and powered by a perpetual motion engine, and shield the craft with a many-worlds sphere projector. Its so simple, when you put it that way.
Personally, I’m buying stock in a gravity radiation drive system [I just hope the ship won’t have to turn!
]. Either that, or I’ll just get more LI batteries for my scooter.
Hey, I don’t have a scooter…
The DC
A strong magnetic field would be effective at deflecting most cosmic radiation. After all, the Earth’s magnetic field does that for us. As for dust and debris, it could be ionized by a laser sweeping in front of the ship, so that the magnetic field could deflect it. Although, yeah, the neutrons would pose a problem.
And a magnetic field wouldn’t help with the EM radiation. At near-light speeds, starlight would be blueshifted to hard gamma. That’s where you pretty much need physical shielding. But I’ve read about some hypothetical engineered materials, maybe some kind of programmable matter, that could duplicate the radiation-absorbing properties of a much denser, thicker material.
capricorn one redux;)?
the dead giveaway is the hamster drive.
I kinda like the nuclear salt water rocket instead of orion. It’s throttleable and it’s continous thrust, but neither has specific impulse to realisticaly get above small fraction of lightspeed. There is website called atomic rockets that deals some rocketship concepts.
Does no-one read SF anymore? Unless I missed it, there’s been no mention on this thread of the Orion spaceship “Michael” which features at the end of Niven & Pournelle’s alien invasion novel “Footfall.”
http://www.up-ship.com/apr/michael.htm
It’s one of the greatest battle scenes in literary SF. Written before even the Challenger was destroyed, it launches the shuttle fleet as fighter-bombers.
“read?” what is this “read” -vanna the drill throll.
I remember first seeing about the Orion concept in Carl Sagan’s “Cosmos”
Pretty impressive. I always assumed an orbital assembly and launch, blowing nukes to get it off the ground never seemed reasonable.
Keeping an acceleration of about 0.5 – 1 g halfway, turning the ship around 180, and decelerate a the same rate seems the easiest way to solve the gravity issue in a long trip.
“Keeping an acceleration of about 0.5 – 1 g halfway, turning the ship around 180, and decelerate a the same rate seems the easiest way to solve the gravity issue in a long trip.”
Except that’s the sort of thing you can only practically do on a short trip, because on a long trip you’d need an impractically huge amount of fuel to keep thrusting that hard for that long. The more fuel you carry, the heavier you get, and the more fuel you have to carry just to push all the fuel you’re carrying. Which rapidly reaches a point of diminishing returns. There’s just no way an interstellar ship can carry enough fuel to accelerate itself to more than a tiny fraction of lightspeed, let alone to thrust continuously for a decade or more.
And this is why, really, the only practical interstellar drives are those where the ship carries no fuel at all — either ramjets, where they collect their fuel en route, or beam-driven ships where the actual “engine” is back in the home system. And ramjets probably wouldn’t work, since their magnetic fields would have a braking effect and since they’d really only be practical inside a nebula or other dense concentration of interstellar gas. (And our Sun resides in a large bubble of low gas density, making ramjets even more impractical in this part of the galaxy.)
Nuclear pulse propulsion would have the advantage of extremely high specific impulse (compared to chemical rockets), and extremely high thrust. Light-driven craft would have the advantage of a theoretically infinite specific impulse (since it doesn’t carry consumable fuel), but would have very, very low thrust. Nuclear pulse craft would therefore accelerate (and decelerate) much, much faster than light-driven ships, and in certain cases could have significantly higher speeds. Depending on a whole host of design variables, their travel time could therefore be significantly shorter than beam craft, especially for nearby stars.
Christopher – Yeah, sounds pretty dismal on the face of it, though I’m sure we’ll get out there with one or more schemes eventually. I doodled out something of a hybrid Enzmann-Bussard type of ship, with a smaller fuel ball than the original Enzmann design, but with a Bussard drive in the tail. The “standard” deuterium fusion engines would be for getting up to Bussard speed and for final slowing down. The Bussard engine -might- be able to handle some of the deceleration, though there remains a big question about sucking in one’s own exhaust, or even blowing potential “good” fuel away from the collector. In any case, we’re probably looking at a ship that contains a large-diameter centrifuge for at least 1/3g.
Mike: I gather that magnetic sails driven by particle beams can potentially have a very high acceleration, multiple gees in fact. A magnetic field can’t melt, so there’s no practical limit to how much energy you can pour into it. Also a particle beam is more efficient than a laser at imparting momentum, and it’s even better if you use pellets or microsails instead of a particle beam, because then you don’t have the “bloom” problem of the charged particles in the beam repelling each other and making the beam dissipate. (A stream of laser-driven microsails of dielectric material could be acclerated near c in literally seconds each. Even a sail a couple of grams in mass would have enormous kinetic energy at those velocities, and if it’s ionized by a laser on the target ship just before impact, most of that energy goes into accelerating the magnetic sail.)
And with no need to carry reaction mass onboard, the ship could be made very light. A magsail is just a big loop of wire, after all. So that would make it even easier to accelerate. Not to mention that the sail could be used for braking against the destination star’s magnetosphere, so there’s no need to carry fuel for that purpose either.
Personally, I’m a fan of self-contained ships that can refuel, so a deuterium fusion craft is my current favorite. With an MHD system built into each engine, we might be able to get back at least some of the energy coming from the reaction. And deuterium could possibly be refined from various sources in other star systems. I’d hate to think that we’d have to rely on Earth- or Sol-based laser or particle beams, but the different types of sails have always been interesting. Bob Forward gave me a thick stack of papers at one point outlining the operation of his multistage laser sail, and while I had no idea what the math was all about, the diagrams told me what I needed to know.
The departure sail was something like 1500 miles wide, with braking and return sails nested inside. That’s a lot of very skinny aluminum. I’m kind of disappointed that we can’t pop even a mini-sail up to test; nobody outside of the Planetary Society seems interested, though I think NASA has some micro-sail payload in the works.
Here’s the doodle I mentioned; it actually involved two sets of six smaller deuterium tanks (somewhat Daedalus-like), with the hab smack in between them. The radiators should probably be twice as long. The hab would be 300 feet in diameter. There would likely be a number of sensors and com antennae/lasers hiding behind doors in the scattershield or on the outer surfaces of the tanks or anywhere else that they wouldn’t be abraded off. Pretty pedestrian design, but I suppose no real ship will be as cool as we make the ones on TV.
http://www.ricksternbach.com/hybrid.jpg
Lightsails are so weak but i always liked the leave the engine at home idea. For initial boosting stage, i was thinkin, if one could make antimatter in near future, maybe nanotech little antimatter bacteria sized bullets, is it feasable to have a kinda antimatter particle beam aimed at a orion like pusher plate that just anihhalates ablates away, than when out of range jetteson and use bussard ramjet?
Well, the official Virtuality Facebook page is up, with all kinds of background info, including the not-yet-mentioned fact that the Orion pusher bombs are matter-antimatter, not your garden-variety H-bombs. So what they’re really proposing is chucking photon torpedoes out the back. How convenient.
Will the Phaeton be an accelerate-then-coast ship? Seeing the blueprints it seems a bit too small to carry enough fuel for anything else, even if it’s M/AM.
What seems more crucial to me is life support-related storage capability: that BBC doco has complementary “making of” videos, one of them discussing food, water, oxigen needs and so: the required quantities for that Solar System tour were enormous.
Yeah- with these kind of drives and how large we are talking- they really don’t take off as much as they push the planet away!!!
JM Busby
On io9.com they’ve posted some sample video from the show. The spacecraft ops dialogue is pretty funny. I’ll have to go back and listen again, but apparently one M/A charge pushes them 15 million kilometers in a few minutes (seconds?) and the journey to e Eri isn’t ten years, it’s FIVE years one way. I still assume that’s ship time, which means that the wavelength stretch to get the shipboard video back to Earth is going to make watching the reality show…ve…ry…slo…ooo…ooww.www. The sample scenes give the impression that this might be a fake trip, and they don’t end up going anywhere; if that’s the case at the end, it will have been two hours of my life I’ll want back.
The kitchen scene with the racks of bottles is also interesting. I wonder how many bottles of hot sauce they’ll use up in ten years.
Maybe hot sauce-spiked antimatter?
I realize technical plausibility in science fiction isn’t what it used to be. They really have so much more to worry about, like what brand of designer sneakers the crew will wear. Hmmm…I wonder if the Discovery Store still carries that BBC space docu-drama…
Alright, the line in the show talked about 19.2 million meters per second, 1/15 of lightspeed. I don’t know where that occurs in relationship to firing the engine for the first time (’cause you never know with editing and trailers), but it seems somewhat unbelievable. Will just have to see what happen on the 26th.
Five subjective years to get the 10.5 light-years to Eps Eri? That means a time dilation factor of about 2.1, which corresponds to a velocity of 88% of lightspeed, or 264 million m/s. And that’s not even counting acceleration/deceleration time.
Correction — I did my math slightly wrong. I forgot to take into account that at less than lightspeed, it’d take longer than 10.5 years to cover that distance. D’oh! You’d actually need to get to fully 90% of lightspeed in order to get a subjective shipboard travel time of 5 years for a 10.5-ly journey.
Any way you look at it, it’s a silly idea. Who’s going to be tuned in to a reality show that takes 10+ years to play out a 5 year trip? Oh, right. The same crowd that watches The Osbournes. “Sharon! Where’s the antimatter?!”
very nice stuff, my first time at your blog , i love the way you write
got yourself a new reader here:)
Hi east bay! Thanks! Welcome! Put your feet up! Set a spell!
Hi All
Travelling at 0.9 c cruising speed means the signal from the ship is red-shifted by sqrt[(1+.9)/(1-0.9)] = 4.4, thus running 5.4 times slower than Earth-time. Would be painfully slow to try to watch or listen to in real-time.
BTW as much as I love Rick’s gorgeous artwork of Enzmann starships – so much so that I have an October 1973 ‘Analog’ magazine so I could have his cover artwork – as originally conceived it wouldn’t work. Enzmann imagined the deuterium would make a nice sturdy ice and thus could be stored as a big solid ball without tankage. So did I. But apparently the mechanical strength of frozen hydrogen/deuterium is more like soft butter – it would need a container after all.
By the time I did the Oct73 Analog cover, Enzmann and a few other folks had decided it would be a smart move to encase the fuel in a big structural ball. The tank was imagined as an inflatable balloon sprayed with metal plasma, and then reinforced, etc. When I did the Science Digest article and paintings in May83, the Enzmann ship still had a structural tank, and that’s about where it sits 26 years later.
Hi again
Of course the 5 years (ship-time) would turn into +20 years for the folks back home, because the signal takes 10.5 years to get back to Earth once the ship arrives after its +11 year trip. Basically the red-shift go slow makes the play-back take >4 times as long as ship-time.
A sneaky approach would be
…let me finish that thought. A sneaky approach is to use a microwormhole to send gamma-ray signals back to Earth from the ship. Thus the ship-show would be seen on Earth in ‘real time’ – but the ’5 years’ of ship-time comes from up to ~15 years in the ‘future’. That’s one reason why wormholes are potential time-machines.
> Orion-type propulsion should at least look interesting on screen, and it would work nicely for a solar system explorer, but no way will it get you to another star. There’s not enough plutonium on the planet to make enough nuclear devices to accelerate a ship to any appreciable fraction of c.
Not necessarily true. Old-school Orions started out with a specific impulse of 1800 seconds for the 10-meter versions, and went up to about 4000 seconds for the 85-foot USAF “battleship” versions, and larger versions still were expected to have Isp’s of about 12,000 seconds. Later in the program, General Atomics developed the “Casaba Howitzer” bomb, which was – from what can be gathered from the declassified literature – a “shaped charge” nuke.” Reports are that preliminary testing was done on the CH warhead design and it was found to be workable. Additionaly, nuclear weapons designer Ted Taylor claimed to have worked out small nuclear charges with sub-critical amounts of plutonium. Put all those together, and sizable Orion vehicles could possibly attain Isp’s well into the tens of thousands, perhaps hudreds of thousands.
The “Medusa” concept Orion from the 1990′s was baselined for an Isp in the area of 400,000 seconds. While nobody is going to be going on day trips to Alpha Centauri with a propulsion system like that, it’s certainly a practical startign point for a starship.
> A second major concern is the radiation from the explosions themselves. It’s a double-edged sword. You need to carry a large ammount of shielding to protect the crew, the equipment, and the supplies. Which with current technology, makes it too heavy.
Untrue! The crew would need to be rad-shielded only during times of active propulsion (and solar flare, natch), and these periods – at least for interplanetary missions – would last only minutes. The General Atomics designs for the USAF had payloads measured in *thousands* of metric tons…. more than enough for some shielding.
> And the explosions themselves cause wear and tear.
Actually, surprisingly little wear and tear. Ablation of the pusher plate could be *completely* stopped byt he simple expedient of spraying a fine mist of silicone oil onto the plate before each blast. And the running temperature of the plate… made of relatively unimpresisve steel alloy… would be less that 300 degrees F.
While the temperature of the bomb plasma can approach a million degrees, the interaction time with the plate – the time the plasma pulse requires to bounce off the plate, transferring its momentum – is measured in microseconds. Additionally, as the plasma starts to pile up on the surface of the plate, it forms an incandescent but opaque gas layer; thus very little of the radiant energy from the plasma actually penetrates to the plate itself.
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