tag:blogger.com,1999:blog-726484495782035142.post6396860136746924894..comments2024-03-28T00:43:37.279-05:00Comments on Future War Stories: FWS Topics: Sub-Light Starship PropulsionWilliamhttp://www.blogger.com/profile/17218428427067689631noreply@blogger.comBlogger26125tag:blogger.com,1999:blog-726484495782035142.post-65217123790949769832023-02-21T18:29:23.888-06:002023-02-21T18:29:23.888-06:00Been mentioned elsewhere on these comments but I&#...Been mentioned elsewhere on these comments but I'd suggest revising the section of the blog on VASIMIR drive to remove references to Pair Production (the creation of matter and antimatter with photons from the sun) as VASIMIR doesn't really have anything to do with that. A vessel with a solid core antimatter reactor could *power* a VASIMIR engine, but antimatter isn't related to it's operation.ghttps://www.blogger.com/profile/01383757122392251096noreply@blogger.comtag:blogger.com,1999:blog-726484495782035142.post-85195772295857476572017-11-07T11:57:25.707-06:002017-11-07T11:57:25.707-06:00Ok. This is a very interesting article but i feel ...Ok. This is a very interesting article but i feel like it only covers a few possibilities of all of these propulsion systems. to start, of course were not going to use Ion thrusters for interstellar travel! Why add them to this article at all? Second, the text on the Antimatter propulsion is interesting but I felt like it could be expanded by a lot. Meaning could you maybe list the feasibility or if said rockets could be sufficient to carry humans in a relatively short time as in could said Antimatter rockets travel to Proxima Centauri B in under a century? Another thing you should add is a more elaborate description on travel time, payload capacity, total mass, fuel mass, dust shield, fuel type, number of people on board , and other such things. <br /><br />The Antimatter VASIMR was a particular interest of mine as it has the ability to refuel itself. But it would be greatly appreciated if you could elaborate on whether it can be manned as a colony ship or if it is a simple probe. I find it to be an interesting design for the type of ship.<br /><br />Regardless of the numerous errors and missing information, I found this post to stimulate areas of my brain prompting me to find out more about the fascinating area of research surrounding manned interstellar travel and other such topics of deep space colonization.<br /><br />-Zev-Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-726484495782035142.post-15124338288719357182016-09-03T01:57:04.298-05:002016-09-03T01:57:04.298-05:00These are the examples of human intelligence and b...These are the examples of human intelligence and brain. This theory of matter and anti-matter is actually very interesting to know as I always read that universe is composed of matter and vacuum.<br />Regards:<br /><a href="http://www.bostonfirearms.com" rel="nofollow">MA Gun License</a><br /><br />Anonymoushttps://www.blogger.com/profile/12455779831351440576noreply@blogger.comtag:blogger.com,1999:blog-726484495782035142.post-46723681904326593232016-04-15T15:57:27.643-05:002016-04-15T15:57:27.643-05:00The anti-matter to FWS, FPS!The anti-matter to FWS, FPS!Williamhttps://www.blogger.com/profile/17218428427067689631noreply@blogger.comtag:blogger.com,1999:blog-726484495782035142.post-43166514572081052352016-04-15T13:39:43.861-05:002016-04-15T13:39:43.861-05:00better: Future Peace stories. Around the World eve...better: Future Peace stories. Around the World everybody must to say: No more Wars...No more Nations...No more Frontierstonyonhttps://www.blogger.com/profile/08253501266473243514noreply@blogger.comtag:blogger.com,1999:blog-726484495782035142.post-14192093559611269472015-10-25T12:45:48.626-05:002015-10-25T12:45:48.626-05:00Great article! There are a few issues with the sci...Great article! There are a few issues with the science, such as engines being described as having a "top speed." Not only does that not usefully describe the capabilities of an engine, the whole notion of speed is especially ambiguous in space travel and completely dependent on one's frame of reference. For instance, when departing Earth orbit and entering Solar orbit, one's orbital speed suddenly jumps from between 3 and 7 km/s up to 30 km/s, even though no acceleration has occurred. The frame of reference has simply changed. A more accurate description of an engine's performance is maximum delta-v, or total change in velocity. Even this is ambiguous, though, because it is strongly affected by the propellant-to-payload ratio of the rocket. If you have more fuel, you can always go faster--regardless of what engine is being used.<br /><br />The Woodward effect and Mustafa drive deserve to be thrown in the trash. They are perpetual motion machines--just like the Dean drive--but with more current pseudoscience thrown around to confuse people. The problem with quantum fluctuations in mass is that they are fundamentally random. There is absolutely no way to change the probability of whether a particle will briefly increase or decrease in mass. When the probability is 50%, there ends up being no net motion. The Woodward drive wiggles its particles back and forth in futility. Even when one invokes spooky quantum physics, the universe always balances its books and conserves momentum at the macro-scale. Always.<br /><br />Also, I'd like to point out that the acronym VASIMR stands for something else. It's another type of plasma rocket, and it deserves to be on this list as well. It's really quite interesting! The main advantage is that it can "shift gears," trading exhaust velocity for greater thrust. This means that it can start out with the oomph and power of a chemical rocket to accelerate hard and break orbit quickly, then it can switch over to "cruise mode" once in deep space, giving the spacecraft the huge exhaust velocity and fuel efficiency of something like an ion engine. It's also very near to being ready for flight.<br />https://en.wikipedia.org/wiki/Variable_Specific_Impulse_Magnetoplasma_RocketThomashttps://www.blogger.com/profile/16649163772390263496noreply@blogger.comtag:blogger.com,1999:blog-726484495782035142.post-21631372664907993452015-01-28T15:21:14.982-06:002015-01-28T15:21:14.982-06:00This comment has been removed by the author.tonyonhttps://www.blogger.com/profile/08253501266473243514noreply@blogger.comtag:blogger.com,1999:blog-726484495782035142.post-73782632914544496722015-01-28T15:20:14.494-06:002015-01-28T15:20:14.494-06:00war in the future?. No thanks. WAR NEVER MORE.war in the future?. No thanks. WAR NEVER MORE.tonyonhttps://www.blogger.com/profile/08253501266473243514noreply@blogger.comtag:blogger.com,1999:blog-726484495782035142.post-47983966021929549492014-11-07T01:02:18.106-06:002014-11-07T01:02:18.106-06:00Hi William
About the beam sails concept – I believ...Hi William<br />About the beam sails concept – I believe you didn’t understand it, the power generator & beam emitter aren’t locate on the vessel but stays at home solar system while the sail propelled by the beam. The mass of the power generator & beam emitter aren’t relevant to the sail acceleration at all.<br />Instead of mass problem there's a deceleration and return home problems:<br />Deceleration – every interstellar vessel must spent a large portion of the journey & fuel on deceleration before enter to destination solar system, since the beam sail don’t have onboard propulsion and the beam at home can only repulse not attract then the sail might served as unmanned probe that just pass thru the target solar system/s, taking pictures and transmitting back home. Like the Voyager probes were.<br />If you want to decelerate the sail then you have to use two stage sail, before deceleration the first stage sail will detached from the second, the beam will be aimed to the first stage that will reflect the beam back to the second stage, the result- first stage continue to accelerate while the second decelerate.<br />Return home – the crew/A.I. onboard will have to construct beam emitter in the target solar system that could push them/it back home.<br /><br />Yoel<br />P.S. congratulation for your new job! <br />Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-726484495782035142.post-22712418448583892472014-08-22T13:16:08.490-05:002014-08-22T13:16:08.490-05:00continued, this site doesn't seem to like post...continued, this site doesn't seem to like posts over 4000 characters.<br /><br />nuclear systems have thrust somewhere on a scale from "decent" to "brilliant" depending which one you choose and delta V on a scale from "nice" to "perfect", the key thing is you trade one for the other. vasimr is not as good as a nuclear system in either respect but it is a pointer of how the perfect nuclear rocket could function with different gears, one for high thrust, one for high delta V, and some inbetween. this gear change is done by getting the engine to put unit amounts of energy into large amounts of reaction mass for high thrust(but low exhaust velocity, which is linearly related to delta V) or the same amount of energy into a far smaller mass of propellant to give it a higher exhaust velocity hence a better delta V. if you can find an engine type that gives high thrust and high delta V you have a "torchship", whether this is possible is currently uncertain but it is clear from the equations that one of the key requirements is a huge amount of power (as in joules per second) going into the reaction mass. one can calculate that to get high thrust and delta V from a fusion motor at the same time might need power requirements similar to earth's overall consumption, it's tough but even a few grams of hydrogen fusing per second could do it.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-726484495782035142.post-65452084857462570402014-08-22T13:14:18.920-05:002014-08-22T13:14:18.920-05:00even for a mars voyage, let alone an interstellar ...even for a mars voyage, let alone an interstellar one, chemical rockets become prohibitively expensive so nuclear power WILL be required. Tree-hugging types must get over the fears and realise that as long as your launch vehicle is reliable then nuclear power in space is a very safe thing to develop and use. the bussard ramjet is another excellent idea and would be ideal for an interstellar flight if certain problems with constructing the massive scoop and the issue of extreme drag due to the hydrogen being collected having to be accelerated to the ship's speed can be solved, if the scoop can be built but the drag issue cannot be beaten there is always RAIR (ram augmented interstellar rocket) which uses onboard power supplies (from fusion, or if we can't dvelop that then fission) fuels but get's it's reaction mass from the scoop. as the reaction mass doesn't need to be accelerated up to the speed of the rocket before it can be used (where hydrogen collected to feed a reactor would need such an acceleration) the drag problem is rather reduced. if a true bussard ramjet, or a RAIR rocket can't be developed then there are options for a fusion powered rocket or a fission powered one. the fusion rocket might use fusion to heat a separate reaction mass or it may use the helium product from the reactions as it's propellant. the fission rocket usually has a fluid pumped past a hot reactor, this heating expands the reaction mass and shoots it from the rear at a nice high exhaust velocity. specifically NERVA was an investigation into using a fission rocket with a hot reactor and propellant being pumped past, your image in the nerva section of this post actually shows the JIMO (jupiter icy moons) probe concept which although it would have carried a fission rector would use it for power generation not propulsion, in the case of JIMO the reactor would supply electrical power to ion or vasimr(vasimr is usually used to mean VARiable Specific Impulse Magnetoplasma Rocket as it is in the case of JIMO) engines where on a nerva craft the reactor directly heats a fluid giving better thrust but possibly slightly lower delta V. also your mention that the technology of nerva would help with a bussard ramjet is somewhat incorrect, a bussard ramjet would use fusion where the nerva program was only ever concerned with developing a particular type of fission rocket(the solid core nuclear thermal rocket to be precise). although the act of developing nerva might give us a better understanding for when the time comes for the generation of rockets after that. the most shocking fact in the end is that we could build nerva rockets TODAY and they would work BETTER than the best chemical propulsion systems in use, it's a real shame that nerva research stopped (largely due to a UN treaty). we could also build orion drives TODAY but they could be a bit messy, their greatest danger to us coming from the EMP they could produce because if launched from some places on earth's surface there would be no-one within the potential fallout danger radius.another propulsion system you might want to consider is a nuclear lightbulb, this is another type of nuclear thermal rocket but this time it is a gas core with the fissioning gas kept safely separate from the exhaust stream it heats by use of quartz walls (hence the name lightbulb). once again the lightbulb is a technology that although it couldn't be built with today's technology it could be built with the tech we WOULD have today IF nerva had been fully developed. in the end the key things for a propulsion system are delta V and thrust, current chemical rockets have plenty of thrust, so can accelerate fast but absolutely rubbish delta V, so burn out before reaching the speeds you need for manned interplanetary travel. ion rockets have great delta V but very poor thrust so are useful for unmanned probes to planets in our system but would be too slowly accelerating to reach another star easily, they could never lift a craft from earth to orbit.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-726484495782035142.post-22311386121400881352013-11-05T14:12:54.404-06:002013-11-05T14:12:54.404-06:00After working on the FTL travel blogpost, I think ...After working on the FTL travel blogpost, I think it is interesting how much sub-light is glanced over and the real work is devoted to FTL technology, while in reality, FTL is a pipe dream, and sub-light is the real challenge. Williamhttps://www.blogger.com/profile/17218428427067689631noreply@blogger.comtag:blogger.com,1999:blog-726484495782035142.post-74825867453511734052013-11-02T21:28:13.269-05:002013-11-02T21:28:13.269-05:00must mention VASIMR is actually VaRiable Specific ...must mention VASIMR is actually VaRiable Specific Impulse Magnetoplasma Rocket, it is a more powerful equivalent of an ion engine. personally my money would be on the bussrad ramjet, it would be a hell of an engineering challenge but if(when might be a better word here) one works it will make interstellar exploration a possibility as opposed to a fantasy.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-726484495782035142.post-59335608392934272042013-06-28T11:39:41.755-05:002013-06-28T11:39:41.755-05:00Time is one way to think about how to select a sub...Time is one way to think about how to select a sub-light drive system. How fast do your characters need to get to Io and back. Then think about level of technology of your fictional world. If they can create Anti-Matter readily, than things are much simpler. Given that Io is very near Jupiter, a prime source for He3, allowing for use of a Fusion Rocket to be a good choice. If you want something different, than Nuclear Pulse Propulsion is a rare drive in scifi. Williamhttps://www.blogger.com/profile/17218428427067689631noreply@blogger.comtag:blogger.com,1999:blog-726484495782035142.post-91386232931618065802013-06-28T10:10:52.941-05:002013-06-28T10:10:52.941-05:00Hi, I've read your series and find it fun and ...Hi, I've read your series and find it fun and interesting; but now I'm planning to write a short story, but need to know just what would be an ideal propulsion system for my heroes. I'm thinking back to "Outland", so in your opinion, what kind of propulsion system would make it feasible to go to "IO" to mine whatever they were mining?<br />Camhttps://www.blogger.com/profile/09008079618808722913noreply@blogger.comtag:blogger.com,1999:blog-726484495782035142.post-67984176431510073492013-02-01T16:12:46.080-06:002013-02-01T16:12:46.080-06:00Alas, your blogpost does contain a few errors, whi...Alas, your blogpost does contain a few errors, which others have remarked on.<br />If you are interested, I have a list of rocket propulsion systems. Google "Atomic Rockets engine list" (most comment systems do not allow including URLs)<br /><br />You did miss one entertaining propulsion system. Google "Zubrin nuclear salt water rocket". Remember the nuclear pulse propulsion from your blogpost? Where the rocket is driven by a series of discrete nuclear detonations?<br /><br />Well, imagine CONTINUOUSLY detonating nuclear rocket. <br />Most propulsion systems are either high-thrust/low-specific-impulse (like chemical rockets) or low-thrust/high-specific-impulse (like ion drive). Zubrin's NSWR is the only one I've ever seen that was both high thrust and high specific impulse. <br /><br />It is a pity that when you ask Zubrin how you keep a continuously detonating nuclear explosion from annihilating your spaceship he gets sort of vague and says "...and then a miracle happens..."Nyrathhttps://www.blogger.com/profile/11528898889244833751noreply@blogger.comtag:blogger.com,1999:blog-726484495782035142.post-63948031458016388242013-01-23T16:50:38.013-06:002013-01-23T16:50:38.013-06:00On UFOs- what is funny is that I have read about f...On UFOs- what is funny is that I have read about flying saucers and our purported alien visitors for years, in everything from books on UFOs to "Chariots of the Gods". <br /><br />I even got my first exposure to the idea of finding ways to achieve starflight with the physics that we have from a book titled "Flying Saucers and Science" by Stanton Friedman, who dismisses pronouncements that interstellar flight is impossible in the second chapter of the book. He suggests that the flying saucers are Earth Excursion Modules (EEMs) coming from giant interstellar motherships which are not suited to landing on planets.<br /><br />However, I have never seen any really conclusive evidence to back the "they-are-here-and-watching-us" school of thought, even though I think that interstellar travel is possible and that the kind of chance communication advocated by SETI is the last way an alien civilization would go about finding and communicating with their neighbors. I do wonder if aliens could have visited Earth a long time ago, perhaps even before human civilization arose, and we have simply never found any traces of this contact. Maybe they are here- but no one has conclusively gone through all the sightings to find conclusive evidence of this, or answered who "they" are.<br /><br />I do think that interstellar flight is possible. Fusion and antimatter annihilation, or even more exotic energy sources, can provide the energy required for interstellar travel. The ship could have a multigenerational crew, or the astronauts could hibernate to sleep through years or decades. Alternatively, if the ship can travel at near-light speeds, the astronauts could take advantage of time dilation to cover vast distances in under a human lifetime. There are just too many different ways to explore the stars at sublight speeds to dismiss interstellar fight out of hand. Probably, there are civilizations out there for whom the invention of interstellar flight is ancient history.<br /><br />Oh, and on "Encounter With Tiber"- I enjoyed the parts about the journey of the Wahkopem Zomos, and Nisuan disaster on Earth. I rather liked the Nisuan landers, especially how they could pump air out of their interior in order to become an aerostat. I never thought of combining a vacuum airship and a rocket. <br /><br />I like the idea of a steam rifle, too, perhaps one could work by rapidly injecting something like sulfuric acid into the water in order to boil it and propel a bullet with the steam explosion. Gives us something different from a standard gunpowder combustion hand weapon.Christopher Phoenixnoreply@blogger.comtag:blogger.com,1999:blog-726484495782035142.post-17670772856129886882013-01-23T16:29:45.388-06:002013-01-23T16:29:45.388-06:00Yeah, American education does not seem to do a goo...Yeah, American education does not seem to do a good job teaching kids about space and space travel. I think that self-education is more important than accepting what you are spoon fed. With the number of books, lecture courses on DVDs, and even streamed science courses from places like MIT, it is easy to learn nowadays. I remember reading the novel version of "2001" and envying the astronauts their electronic teaching consoles, but nowadays that sort of tech is real- I've found science and math courses streamed from places like MIT on youtube!!<br /><br />For reference, C is approximately 300,000 km/s or 186,000 miles/sec., so you can convert to and from % of C pretty quickly by converting a speed into the appropriate units and dividing by the speed of light to get the decimal form. For instance- 13,110 km/s would be 13,110/300,000=0.0437, or 4.37% C. Fast enough to reach Alpha C in 100 years. Obviously, I chose those numbers because of that. Heh. It can be surprising how fast even "slow" speeds are in space- at those speeds, a starship would reach the Moon in thirty seconds!! That is a distance the Apollo astronauts took three days to cross, and this thing would do the same in thirty seconds but still takes a century to reach the nearest stars.<br /><br />Well, the one thing I wanted to make clear was that no matter how many different sub-types of plasma engines you might see, they are all just rockets. The things to keep in mind are how much thrust a rocket can get from its fuel, and how long that fuel will last.<br /><br />Propulsion schemes based on the quantum vacuum are oddly popular both in speculation on starflight and in a number of SF stories. I think the reason why is that pushing a payload to very high speeds necessarily requires a LOT of energy, as kinetic energy increases by the square of the speed. So, even when you accept the difficulties of having no warp drive, you face the problem of how to get your massive relativistic starship up to speed. A virtually limitless source of energy found in every cubic centimeter of space would obviously be very helpful, if we could tap it. The "quantum ramjet" would convert energy from the quantum vacuum into radiant energy, and use radiation pressure to push the ship.<br /><br />Additionally, these systems have something of an air of plausibility because of the Casimir effect. When two metal plates are brought close together, about a few atomic diameters apart, they exclude some wavelengths of the virtual photons popping in and out of existence between them, and create a force that either pulls them together or repulses them apart. This force supposedly has to do with the zero-point field. This is very complex physics and not for the uninitiated, but it is odd to know that "empty" space does create forces we can detect.<br /><br />Here is an interesting discussion of various fictional plausible starships, including the Wahkopem Zomos and the Venture Star from AVATAR. http://www.icarusinterstellar.org/blueprints-for-a-starship/Christopher Phoenixnoreply@blogger.comtag:blogger.com,1999:blog-726484495782035142.post-36674428272596157282013-01-23T09:04:05.243-06:002013-01-23T09:04:05.243-06:00Oh...I wanted to make another point on the blogpos...Oh...I wanted to make another point on the blogpost but did not. Given my belief in UFOs...I know, very Fox Mulder of me, but there is someway that they or them are coming here. Even if, some of the crackpots online believe, that the aliens have a lunar base, they still came from some other star system. If they can do it...why can't we? Travel between stars is possible if they have been coming here since the dawn of human civilization. Williamhttps://www.blogger.com/profile/17218428427067689631noreply@blogger.comtag:blogger.com,1999:blog-726484495782035142.post-21374509952587991792013-01-23T08:59:27.063-06:002013-01-23T08:59:27.063-06:00What kills me about this subject is that the Ameri...What kills me about this subject is that the American education does a shit job on educating kids about the real nature of space and how we could get to point b from a...too many people, me included, had science fiction to teach them. I think you avoided that Mr. Phoenix, which is good for this blogpost!<br />Some of the propulsion systems were hard to get firm number on % of C, math and I just do not get along! I plugged some numbers in and then were was debate on different sites about % of C...ugh. <br />Thanks for clearing those points up! Another point that confused the hell out of me was how many sub-types of different engines. There were lists of plasma fusion type engines and I couldn't bring myself to list all of them. Seriously, it would have Jack and Cokes until I passed out!<br />Some of the more exotic drive systems took me quite a bit of reading and I threw some out, like the zero-point systems...sounded too Black Mesa for my tastes. I've read of vacuum based systems, but it seems so odd to me. <br />When deep space exploration does happen, it could be like early automobiles, where different engines and fuel types were tested or we could even have the VHS/BetaMax wars all over again!<br />Gee Force in terms of space travel is one of those elements I'm still getting used to. Dude! You totally mentioned Encounter with Tiber! Haven't thought about that book in a decade!<br />Chief Engineer Phoenix has a nice ring to it...<br />Thanks for reading and commenting!Williamhttps://www.blogger.com/profile/17218428427067689631noreply@blogger.comtag:blogger.com,1999:blog-726484495782035142.post-28403917317902514072013-01-22T18:56:55.011-06:002013-01-22T18:56:55.011-06:00Man, I seem to have made a longer comment than the...Man, I seem to have made a longer comment than the blogpost!! D: But, I cannot help it.<br /><br />In regards to acceleration- you are right that it is unhealthy for astronauts to be under accelerations much than 1g for prolonged periods of time, but 12g is not quite chunky salsa territory if you are safely strapped in. Modern day fighter pilots withstand 10-12g during acrobatic maneuvers. By 25g and over, though, you are quite likely to be injured. The highest acceleration ever reached by a human was about 46.2 g during a rocket sled experiment, and the subject suffered some damage to his vision. <br /><br />The Stansilaw Lem book "Return From the Stars" gives some unpleasant details as to the woes of high acceleration as experienced by the interstellar crews. During training, the astronauts are made to endure accelerations so high blood squeezes through the pores in their backs!! After returning from their flight, they find that their muscles have built up to a point that they look like Hector out of the Trojan War because they hibernated at 2g for prolonged periods of time. In Buzz Aldrin's "Encounter With Tiber", the alien Nisuans immerse themselves in fluid and fill every body cavity with supporting gel in order to withstand tremendous, deadly accelerations in the early phases of their interstellar flights.<br /><br />Ironically, one paper I have read on interstellar probes indicates that accelerations over 1g do not cut down the timespans of flights to nearby stars by much, so maybe our crews won't have to endure the crushing accelerations faced by those fictional astronauts.<br /><br />Damn, I just never shut up when we get on this topic. I should sign these comments, "A Starfleet Cadet". XD I guess you could guess where I would end up if I lived during the 23rd century...Christopher Phoenixnoreply@blogger.comtag:blogger.com,1999:blog-726484495782035142.post-26058304651011665482013-01-22T18:46:12.692-06:002013-01-22T18:46:12.692-06:00Nuclear pulse propulsion seems to be pretty slow- ...Nuclear pulse propulsion seems to be pretty slow- Freeman Dyson's nuclear pulse starship would take several hundred years to reach the nearby stars, and perhaps longer. <br /><br />I haven't seen any discussion of using pure antimatter bombs for propulsion, perhaps because it easier to extract energy from M/AM propellent in a steady burn rather than a messy explosion. Antimatter-catalyzed pulse propulsion uses small amounts of antimatter to trigger subcritical fissionable fuel, or to trigger pellets of fusion fuel. So, they are really just a sanitized version of the original concept. So, too, is the Daedalus rocket- triggering fusion pellets with electron beams is not quite as controversial as actually using bombs, but we can use bombs today.<br /><br />I have not heard of Mustafa's drive, but Woodward's Mach effect drive has been knocking around for a while. Efforts to find "breakthrough" space drives have been around for a while- google the Dean Drive and you will see what I mean. Quite a few cranks have been involved, too, so be careful what you reference. Marc Millis's discussion of what would be required is pretty good, you should google the Breakthrough Propulsion Physics project. They have a good website that discusses WHY interstellar travel is so tough, and what we are trying to do to crack the problem. The problem with all these "breakthrough" ideas is that they require currently unproven physics concepts, so they aren't even at the point where we know if they are possible, let alone at the point of building one. <br /><br />http://www.nasa.gov/centers/glenn/technology/warp/warp.html<br /><br />In terms of breakthrough sublight drives, I would have mentioned the idea of an idealized "space drive" that converts onboard energy totally into thrust without expelling exhaust. This would seem to fly in the face of conservation of momentum, so it would have to involve new physics that would describe "something" in the vacuum of space that we could push against. Maybe, if we changed space behind the spaceship, space would then push on the craft and move it- a bit like those soap boats being driven along by a drop of detergent. All this is purely hypothetical at this point. We don't even know if physical law will allow for such craft.<br /><br />Some other exotic drives, featured in some SF stories, are those that use the quantum vacuum. We now know that the seemingly "empty" space around us roils with activity in the quantum realm- particles pop in and out of existence all the time, and it may be that a cupful of vacuum contains enough energy to boil away all the oceans of Earth, according to some calculations. This is all very, very complex physics and some scientists question if our calculations reflect physical reality, but quantum vacuum is real and does in fact cause forces, as seen in the Casimr experiment.<br /><br />Some people have proposed starship drives based on tapping the quantum vacuum, sometimes termed "quantum ramjets". If we could tap almost infinite energy from empty space, we could accelerate to very high speeds without using any fuel- and the whole universe would be open to us. Such drives are sometimes called "quantum drives", "zero point energy drives", or "GUT drives" in fiction. Unfortunately, we don't know if the quantum vacuum can in fact be tapped, and it sounds a lot like something for nothing to me- so this is just speculation for now.<br /><br />It has also been suggested that the quantum vacuum might be responsible for inertia, so if we could somehow manipulate the vacuum, maybe we could make "inertia drives". This is also still only speculation, so no inertialess starship for you yet. I would be worried about the possible effects of lowering inertia on living organisms- would we die when our blood lost all inertia and raced through our bloodstream at hundreds of miles per hour?Christopher Phoenixnoreply@blogger.comtag:blogger.com,1999:blog-726484495782035142.post-18967066092154691692013-01-22T18:09:00.904-06:002013-01-22T18:09:00.904-06:00You discussed several types of rockets. However, ...You discussed several types of rockets. However, antimatter rockets are the only ones that show potential for fast interstellar flight- you list two, the VARIES system and the one shown in AVATAR. Fusion rockets might be able to allow us to launch something at 10% of C, possibly, but require very large amounts of fuel- just look at the size of that rocket!!<br /><br />The kind of antimatter rockets that might be used for interstellar travel are the plasma core and beam-core antimatter rockets. Plasma core engines would heat a large mass of propellent by injecting antiparticles, and exhaust the resulting high-temperature plasma with magnetic fields. In a beam-core engine, and equal amount of particles and antiparticles would annihilate and the resulting pion explosion be directed out the back.<br /><br />VARIES includes a bank of solar panels and an antimatter maker to allow the rocket ship to refuel itself at the destination star. If the ship can refuel itself without relying on antimatter from home, the astronauts will have fuel for the return journey, and they won't have to drag it all the way from home.<br /><br />VARIES is not the VASIMR system, which is a plasma rocket that is currently being tested. VARIES's maximum velocity will be well over 125 miles per second, which is only .067% of C according to my calculator- 6% of C would be over 11,000 miles per second. 125 mi/s is the quoted speed of the Solar Probe Plus, which would take 6,450 years to reach a nearby star. VARIES would take a crew to another star and return to Earth within their lifetime, so it must travel much faster.<br /><br />You also mention ramjets. Ramjets are an effort to get around the mass-ratio problem by scooping up the very thin interstellar medium for use as fuel in a fusion the rocket. The problem is that the ion scoop would likely create more drag than thrust, and what we can scoop up is not good fuel for fusion reactors. One variant would only use the scooped up mass as propellent, in what is called a Ram Augmented Interstellar Rocket (RAIR). The idea of gather up our own propellent as we go along is a valuable one, though, since with an unlimited supply of fuel the ship could accelerate continuously to near light speed.<br /><br />Various proposals involving very large lightweight sails can make closes approaches to the sun, or be pushed by various beamed energy sources (laser, pellet stream, etc.) to reach high speeds. However, these have their own limitations, including the high energy requirements and the attenuation of the beam with distance. They do not have to carry any fuel or engine, however, which makes them quite valuable.Christopher Phoenixnoreply@blogger.comtag:blogger.com,1999:blog-726484495782035142.post-35276307780254957312013-01-22T17:41:02.810-06:002013-01-22T17:41:02.810-06:00Hi, William!! I enjoyed this blogpost- spacecraft...Hi, William!! I enjoyed this blogpost- spacecraft propulsion has always been one of my favorite subjects. I would like to make a few corrections to your list, though- I spotted a few errors, possibly from your sources, and the list on the whole seems a bit haphazard. "Crackpot physics" space drives that rely on vacuum energy don't really fit right next to plasma engines that are already running in laboratories, and said plasma engines don't really classify as starship drives unless you intend to wait for well over 10,000 years to reach Proxima Centauri.<br /><br />A number of the propulsion systems you mention are rockets, which work by expelling propellent out the back in order to be pushed by the reaction force. Whether a rocket expels the products of chemical combustion or a gentle stream of ions, all rockets have two main limitations- the amount of force they get in respect to propellent used per unit time, which is called specific impulse (ISP), and the amount of thrust the engine can generate. Rockets are limited by the amount of propellent they can carry and how much total thrust they can get by expelling all this propellent. Basically, ISP is kind of like the MPG of a car. A low ISP means that you get less total amount of force per unit mass of your propellent, and must carry a lot of propellent to get where you want to go. The thrust of engine is important if you want to take off against the gravitational field of a planet or get up to speed quickly. <br /><br />Chemical rockets can have very high thrust, but guzzle the gas. Ion rockets are very low thrust (and could never take off of a planet), but can keep running for months and eventually hit very high velocities. The ISP is related to the exhaust velocity of the rocket, that is, how fast the propellent is going when it is spewed out. The exhaust from a chemical rocket is relatively slow compared to the speeds we wish to reach (about 3km/s from what I've heard), while an ion engine expels neutral plasma at a much higher velocity, thus getting a much higher ISP.<br /><br />Our basic problem is respect to interstellar travel, is that the distances are very, very large (tens of trillions of miles!!) and even getting there in sometime closer to a century requires very high delta-Vs (term for change in velocity, the proper term for evaluating the total amount of go you can get from a rocket). But, all are current rockets- even more efficient ones like NERVA nuke thermal or super-duper ion engines- require such huge masses of propellent for even slow interstellar flights it is just absurd, and at feasible mass ratios (the ratio of how much of the rocket is structure and payload to how much consists of propellent for the every-hungry rockets) you just take too long. I don't know exactly how long it takes to turn into a skeleton, but 10,000 years is undoubtedly more than enough time for your skeleton to crumble into dust before you even approach Alpha C.<br /><br />So, in addition to the speed problem, we have the propellent mass problem. The obvious solution is to try to build even better and more powerful rockets with ever greater fuel-mass to energy conversion ratios and ever higher exhaust velocities- thus ever higher ISPs. This was the insight of the German rocket engineer Eugene Sanger, who imagined jet propulsion systems based on nuclear energy in which the exhaust stream is a beam of light, and the radiation pressure pushes the ship. If we want to travel at significant fractions of the speed of light, our exhaust velocities must be close to the speed of light- high energy jets of energetic particles or photons powered by fusion or antimatter annihilation. At the very least, our exhaust velocities must be much greater than those we play with today. This is why we look into antimatter rockets and so on- with a exhaust velocity as high as antimatter might allow, we can achieve missions impossible with todays chemical or even nuclear rockets.Christopher Phoenixnoreply@blogger.comtag:blogger.com,1999:blog-726484495782035142.post-53200816730363523382013-01-22T10:00:13.368-06:002013-01-22T10:00:13.368-06:00This is one of those blogposts that I am simply ou...This is one of those blogposts that I am simply out of my element on. Physics was never my strongest subject, and reading some of the professional research papers drove me to drink. But, I felt like it was important to list the major hard-science sub-light propulsion systems, and the high points of them. I'm just glad you enjoyed it.<br />Thanks for reading and commenting!Williamhttps://www.blogger.com/profile/17218428427067689631noreply@blogger.com