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What Is The Future Of Space Travel?

The future of space flight


What Is The Future Of Space Travel?

The use of chemical based rockets to leave our planet and explore space may very well be a dead end technology. It’s old, outdated and it’s extremely inefficient. Surely we’ve discovered or improved upon newer, more efficient technology in these last 60 years, right? The answer to that is yes, and we’re going to go over them in detail.

We will explore exotic technology that includes using solar wind to sail amongst the stars, using nuclear bombs to approach light speed, and even dabbling with technology that exploits loopholes in the laws of physics which NASA has recently been experimenting with.

What’s Wrong With Chemical Rockets?

Chemical rockets may be a dead end because of their extreme inefficiency. Just to put the space shuttle into earth orbit (to reach 17,500 MPH), the rockets need to carry 15 times its weight in fuel – and that’s considered extremely efficient among other chemical-based rocket systems. To escape earth’s gravitational pull and explore our solar system (to reach 25,000 MPH), you would need significantly more fuel.

Space ShuttleOccasionally, space agencies can mitigate some of the problems by using gravitational assists from planets. They use a planet’s gravity well to slingshot a probe toward its destination, significantly speeding it up.

The problem with this solution is one of availability. To take advantage of a planet’s gravity well, the planet has to be in a specific place, at a specific time. This leaves a small window which a probe would need to be launched. Some of these windows can be incredibly rare. The Voyager space probes, which explored the planets in the outer solar system, took advantage of a planet alignment that happens only once every 176 years.

Then there is the cost. The average cost to put the space shuttle into orbit is 450 million USD per mission. That’s a huge price tag just to reach low earth orbit, and it’s also a big part of the reason the shuttle program was scrapped. If we wanted to leave earth orbit and explore our solar system with such an inefficient technology (without gravitational assists), the problems become severely compounded. Because there aren’t any fuel stations in space, a spaceship has to carry all its fuel with it, fuel which is not only pricey, but heavy.

If we wanted to leave our solar system and travel to our closest neighboring star in a reasonable time frame (say, 900 years) using standard chemical-based rockets, it would require 10137 kilograms of fuel – that is more fuel than exists on our planet. Thus, we need to look towards developing a better, more efficient method of propulsion.

Solar Sails

Solar sails do exactly as the name suggests; they sail on the solar wind. There is no actual wind in space because space is a vacuum, but there is something similar that a spacecraft could use to propel itself. A craft equipped with a giant sail made out of ultra-thin mirrors can harness a combination of light and high speed ejected gasses from the sun to reach incredible speeds.

Solar Sail Japan

Japanese Ikaros Solar Sail

The pressure of the light and gasses is very small, but since there no friction in the vacuum of space, it allows that small pressure to build up over time. Given enough time, this pressure can propel a craft to a significant fraction of light speed. The time to reach top speeds could be lessened by aiming extremely powerful lasers or masers at the sails from a base on the moon or other satellite without an atmosphere.

However, a solar sail does have its drawbacks. Once far enough away from the sun (and any laser boosting stations we have setup), the craft would no longer be accelerating and instead rely on its own inertia to travel to its destination. The craft would then have to direct its sails towards the destination star to decelerate and slow down.

Solar sail spacecrafts became a reality when, back in May 2010, the Japanese launched the Ikaros probe. It successfully deployed its solar sails and is currently in a wide orbit around the sun. It’s expected to reach Jupiter in a few years.

Ion Drive

An ion thruster (or ion drive) is a lot less exciting than how it is often portrayed in science fiction books and movies. It operates on similar principle as the solar sail; using very low thrust but over an extended period of time. It achieves this thrust by ejecting charged ions, gas or plasma out of its electric engine which propels the spacecraft.

Ion Thruster

Ion Engine Test

This method of acceleration allows a craft to achieve a very high specific impulse. Such a craft would only work in the vacuum of space since the thrust is so low. However, the fuel required by the engine is significantly less than is required by chemical rockets which maxes out thanks to the Carnot limit (a limit on efficiency).

This technology is being heavily considered for future space missions and has already proven its feasibility in space. In 1998, NASA launched the Deep Space 1 probe which was powered by a xenon gas ion engine and was the first ion drive in space. In 2003, Japan launched the Hayabusa probe which used 4 xenon ion engines. Its mission was to rendezvous with an asteroid and collect samples. It completed its mission and returned to earth in June of 2010.

Like the solar sail, ion drives also have their drawbacks. First, they would need to carry their fuel with them. While the amount required to get the nearest star is technically feasible, it wouldn’t be very practical. Travel time is another issue. While an ion drive is significantly more efficient than rocket engines, and is great for jaunts around our solar system, interstellar travel is another matter entirely. With a gravitational assist from our sun, it still would take 19,000 years to reach Proxima Centauri with a ship using an ion engine.

We need more speed if we want to leave the confines of our solar cradle.

Nuclear Propulsion

If we wanted to get to our nearest neighboring star using the best technology available to us right now, nuclear propulsion is our best option. It’s fast, proven and relatively cheap. A ship equipped with nuclear pulse propulsion and could theoretically reach 12% the speed of light. That is so fast, you could travel completely around the earth and end up back at your starting point in just under 2 seconds. Or you could travel to the moon in 13 seconds – it took Apollo 11 four days to reach the moon by comparison.

Orion Project

Nuclear Pulse Propulsion

While it would take 19,000 years to reach Proxima Centauri with an Ion Drive, it would take a relatively manageable 35 years using nuclear pulse propulsion. A human would be able to travel to our nearest neighboring star within his or her lifetime. And it could be done with technology that already exists.

The way nuclear propulsion works sounds a bit crazy, but it is proven and it is relatively simple. Small nuclear bombs are dropped out of the back of the spacecraft which detonate. The resulting force from the explosion accelerates the craft. This is done repeatedly until the desired speed has been attained. An incredibly large, reinforced pusher plate would shield the craft from damages and radiation while dampeners would be used to mitigate the effects of G force and provide smooth acceleration.

The US military began looking into nuclear pulse propulsion back in 1958 under the project name “Orion”. The project was shelved in 1963 thanks to the Partial Test Ban Treaty which prevents nuclear devices being detonated in space. The idea wasn’t forgotten however. In 1973, the British Interplanetary Society developed a similar concept, called Project Daedalus. Then in 1998, the nuclear engineering department at PSU began developing two improved versions of the Daedalus design known as Project Ican and Project Aimstar.

One of the obvious drawbacks to nuclear pulse propulsion is that you have to carry your fuel with you. This means carrying hundreds or thousands of small nuclear bombs. There is also the problem of ablation of the pusher plate. Repeated exposure to nuclear blasts will cause erosion if not sprayed with a special oil before each detonation. Yet another problem is nuclear fallout. This could be averted if a craft is launched from a polar region, or if a craft is launched into space using conventional rockets, then once far enough away, began using its nuclear propulsion.

The late Carl Sagan once suggested that nuclear pulse propulsion would be an excellent use for our current stockpiles of nuclear weapons.

Nuclear Fusion

A spacecraft equipped with a nuclear fusion engine could explore our solar system without the need to carry a large fuel supply thanks to its efficient, long-term acceleration capability.

Fusion Rocket Engine

Theoretical Fusion Engine

There are two ways a fusion engine could work. The first is using the energy created by a fusion reaction to generate electricity. This electricity could be used to superheat plasma which then would be ejected out the back of the craft, providing thrust. The second method would be more direct. It would use the plasma-based exhaust from the fusion reaction to provide thrust.

The drawbacks of a fusion engine are very similar to that of the ion drive. While fusion is a huge improvement over ion drives, it would be very hard to achieve the higher speeds necessary when traveling between stars. Fusion technology is also still in the experimental stage of development. The technology must overcome hurdles with plasma confinement to become viable, then a reactor would need to be miniaturized to a size manageable for a spacecraft. Currently, experimental laser-based ICF reactors are as large as football stadiums and are struggling to break even with power output.


Antimatter is the most potent fuel source that we currently know of. It’s also the most efficient. Antimatter is as the name implies, matter which has its charges reversed. When antimatter comes into contact with normal matter, the two annihilate one another in a ferocious blast of pure energy. A piece of antimatter the size of a small coin contains enough energy to propel a fully loaded space shuttle into orbit. Once in orbit, NASA claims that a trip to Mars would only require as little as 10 milligrams worth of antimatter.

Antimatter ship

Spacecraft with antimatter engines

An engine using antimatter is pretty simple in its operation. A beam of anti-electrons is released into an engine core where it annihilates the surface of a metal plate. This creates a small explosion which propels the craft forward. Another proposed design uses a sail, similar to the solar sail described above. A cloud of anti-particles is released which then reacts explosively with surface of the sail. This reaction can propel the craft to incredible speeds. According to NASA, an antimatter powered craft would be able to reach speeds up to 70% the speed of light. That means we could reach Proxima Centauri in just under 6 years.

The drawbacks of using antimatter are production and containment. Antimatter is a byproduct of atom-smashing tests done at particle accelerators. Tests which are very expensive to operate. If we wanted to produce a single gram of antimatter, it would cost over a trillion dollars. Containment is also another issue. Since antimatter violently reacts when it comes into contact with normal matter, it would have to be stored in vacuum containers at incredibly low temperatures, suspended by strong magnetic fields. This becomes a challenge because anti-electrons (positrons) repel each other, often explosively. Some solutions have been proposed, one suggests that by combining positrons with electrons, researchers can create an element called positronium which can theoretically store the anti-electrons indefinitely.

Faster Than Light

Faster than light travel is just the stuff of science fiction, right? After all, didn’t Einstein say that the speed of light is the ultimate speed limit? Not necessarily, claim physicists. The devil is in the details. According to physics, there are ways around the universes ultimate speed limit. These technical loopholes could theoretically and potentially allow us to race a beam of light, and win.

NASA researchers know that nothing can accelerate faster than the speed of light, but they also know there is no such restriction regarding space itself. Spacetime has no such limit on how fast it can move, and it is believed that spacetime exceeded the speed of light during the expansion of the big bang. Researchers at NASA’s advanced propulsion division have been wondering if spacetime can make a repeat performance.

warp drive

Warping Of Spacetime

A warp drive, normally the stuff of science fiction, would travel faster than light by riding on a wave of spacetime. It creates this wave by compressing the spacetime in front of the ship and expanding the spacetime behind it. A ship then sits in the middle of this wave, and is propelled through space. Since the ship itself isn’t moving, and only the spacetime around the ship is moving, no laws of physics are broken.

At NASA Eagleworks, researchers have begun to attempt to prove the concept of warp drive with lab experiments. There, the researchers set up a mini warp drive called the “White-Juday Warp Field Interferometer”. The experiment seeks to generate a very tiny instance of a warp field. A warp field that is so small, it is only expected to perturb spacetime by one part in 10 million. While the results will be underwhelming if successful, it will be existence for proof of concept. The location for the new project is the facility that was built for the Apollo program, the very same one that put astronauts on the moon.

The first scientific paper which took warp drives seriously was written in 1994 by Mexican physicist Miguel Alcubierre. Alcubierre’s paper called for enormous energies to power his theoretical warp drive. The mass-energy equivalent of Jupiter. Harnessing that kind of energy is impractical and virtually impossible, so his paper went largely ignored.

In October of 2012, at the 100 Year Starship Symposium, NASA researcher Harold White gave a presentation where he announced that he discovered loopholes in the mathematical equations. Loopholes which brought down the energy requirements to levels much lower than previously thought. He calculated that by altering the design of the warp engine and the ship itself, he could get the energy requirements down to just a few thousand pounds of mass. This advancement, and others like it, edge warp drives ever further out of the realm of science fiction and closer to reality.

Stephen Clark (20 May 2010). “H-2A Launch Report – Mission Status Center“. Spaceflight Now.
Shiga, David (2007-09-28). “Next-generation ion engine sets new thrust record“. NewScientist.
“Antimatter Space Propulsion at Penn State University (LEPS)”. 2001-02-27.
G. R. Schmidt (1999). “Antimatter Production for Near-Term Propulsion Applications“. Nuclear Physics and High-Energy Physics.
Dr. Harold White (2012). “Abstract: Warp Field Mechanics 101” NASA Johnson Space Center. PDF
Eagleworks Laboratories (2012). “Advanced Propulsion Physics Research” NASA Technical Reports.



  1. Steve D

    December 23, 2012 at 4:21 pm

    The Orion option (the nuclear spacecraft) is still limited by the colossal energy involved. To get to Alpha Centauri in 35 years would require 10% or more of the speed of light. To keep people sane and supplied for that long would take a big ship – I really don’t see anything smaller than an aircraft carrier. To get 100,000 tons to 10% of the speed of light requires 4.5 x 10^20 joules or US energy output for 50 years. A kiloton is about 4.5 x 10^12 joules, so you’d need 100 million small nuclear bombs. If you can get by with 10 kg of fissionable material per bomb, that’s a billion kilograms or ten times the mass of the ship. Bottom line is there is NO other known method of propulsion in space than reaction.

    Oh, warp drive doesn’t require only a few thousand pounds of mass. It requires the ENERGY of a few thousand pounds of mass. Mass times c squared. And a thermonuclear weapon converts only a few grams of mass into energy.

    • Warp

      January 2, 2013 at 11:53 am

      Well, not the reactions with antimatter. Wich was discussed just above the “warp drive”. That way you get the full pure energy potential of both particles.

      • Altitude

        February 27, 2014 at 11:19 pm

        You show me where to find a stockpile of a couple kilograms of anti-matter, and I will suggest that you and I run as fast as our legs can feasibly carry us in the opposite direction of that stockpile.

        An interesting idea… In the lab, matter and antimatter usually are created together, yet we do not see the signs that antimatter exists anywhere in the visible universe (matter exists in the visible universe; if it ever came into contact with antimatter, we would expect to see signatures of a very specific type of gamma radiation showing up randomly in the sky… we don’t). So that leaves the non-visible part of the universe… which is too far away from us to observe. Is it possible that the antimatter that should have been formed with matter during the big bang could be out there in the farthest reaches of our universe, far beyond the light radius?

  2. Kyle

    December 23, 2012 at 7:08 pm

    Actually, fuel is the cheapest single expenditure in most space launches, as the cost of liquid hydrogen and liquid oxygen for the space shuttle system added up to a few hundred thousand dollars per mission (typically getting up to about 1 or 2% in cases where the engines were repeatedly started and stopped due to launch scrubs). The solid rocket boosters were more expensive, not because of the cost of the fuel — which was again quite cheap — but for the cost of assembling the rockets in Utah and shipping them all the way to Florida to be stacked with the orbiter and the fuel tank.

    The second even bigger problem is that of the six alternative technologies listed here, not a single one of them is in any way feasible for powering a spacecraft out of Earth’s gravity. Even nuclear propulsion — the closest contender for this — can’t be used inside of an atmosphere without producing radioactive contamination equivalent to the detonation of a small nuclear device, and the cleanest version of it — Nuclear thermal propulsion — still uses enormous quantities of liquid hydrogen which would run into your non-existent “fuel is expensive” problem.

    The problem isn’t that chemical rockets are obsolete or inefficient. The problem is that there aren’t any PROFITABLE endeavors going on that require a human presence. This is a problem because, right now, all of the money in space flight is being made in the launching of satellites and (more recently) in unmanned resupply of the International Space Station, thus space EXPLORATION remains a high-loss proposition and is hard to justify financially. The moment this is no longer the case — the moment humans find a way to actually turn a profit from manned spaceflight — even the most inefficient chemical rockets will open the universe for us.

    • Wombat

      December 23, 2012 at 9:20 pm

      fuel is the cheapest single expenditure in most space launches

      No, this is absolutely incorrect. On NASA’s website, they say it costs roughly $10,500 per pound to put something into low earth orbit (LEO). Never mind medium or high earth orbit, or escaping earth’s orbit all together. If it was as cheap as you suggest, we’d already have men on Mars.

      The problem is that there aren’t any PROFITABLE endeavors going on that require a human presence.

      Do you realize how many resources are available in space that companies would kill to be able to access too (and profit from)? If it was cheap, efficient and simple to get to space, we’d already be mining asteroids for rare elements or the moon for Helium-3. The entire point of companies like SpaceX is to make space flight cheaper and more efficient. Right now, it’s insanely expensive to put things into space.

      • MR. Green_dragon

        December 25, 2012 at 12:02 pm

        I would just like to point out the fact that our own history shows that greed runs the corporate world. Granted WE are aware of the fact that there are potentially limitless sources of energy. But there is a catch, say we do find endless supplies for whatever. Supply is no longer is a problem, so the prices drop. Soon everyone is on the same level. Now some would see this as a loss of power or control, but imagine that the people got together and said “Lets use the moon as a power station and beam the energy back in some form”. If you have enough energy that electricity isn’t a concern, you have taken power/control away from someone. The reason space travel isn’t running rampant is because the government are the ones that have the power/control. YOU & I can’t build spacecraft OR aircraft. Why? Yes, it’s dangerous, but I’ll bet when the Wright brothers flew their first few planes, they crashed. As with everything, there is trial & error but knowledge is power. I know many inventors and they have had projects confiscated and told forget about it. Many people look at a Tesla coil and see a device that makes lightning, but that is only a byproduct. It was originally intended to transmit energy without a need for wires. Since it wouldn’t have benefited manufactures as much, it becomes similar to the story of hemp.

      • Kyle

        January 2, 2013 at 12:53 pm

        First of all, the “cost per pound” to lift payload into orbit is calculated from the cost of the LAUNCH, divided by the payload placed into orbit. In this case, $450 million divided by approximately $43,000 lbs (the maximum amount of cargo that can be carried on the space shuttle). As of 2002, liquid hydrogen costs 34 cents per pound and liquid oxygen costs 21 cents per gallon. The shuttle carried 234,000 lbs of hydrogen and 1.3 million pounds of oxygen. That means that with 2002 prices, the FUEL cost was $80,000 for the hydrogen and $273,000 for the oxygen, for a total of $353,000 per launch. When you add in the 5000 gallons of diesel fuel used by the transporter crawler that carried the shuttle to the launch pad, then NASA spent about $390,000 per launch on fuel; that is, 1/1000th of the cost of a shuttle launch. So I repeat: Fuel is NOT a significant launch cost.

        Second of all, I DO realize those resources exist. Evidently so does James Cameron, since he recently dropped half a billion dollars founding Planetary Resources LLC, a company whose stated goal is to eventually mine asteroids for profit. And you’re right, companies like SpaceX ARE making space flight cheaper, more efficient and more accessible to everyone… and they’re going to do it using chemical rockets.

      • Edward Wright

        January 6, 2013 at 3:47 pm

        “No, this is absolutely incorrect. On NASA’s website, they say it costs roughly $10,500 per pound to put something into low earth orbit (LEO).”

        That statement is out of date — and even if it were correct, almost none of that is due to fuel cost.

        “If it was cheap, efficient and simple to get to space, we’d already be mining asteroids for rare elements or the moon for Helium-3.”

        Not until someone comes up with a working Helium-3 reactor.

  3. Edward Wright

    January 6, 2013 at 3:42 pm

    “Chemical rockets are a dead end because of their extreme inefficiency.”

    This is a myth. Chemical rockets are among the most efficient engines ever designed. Nearly all of the chemical energy in rocket propellant gets converted into useful kinetic energy on orbit.

    The cost of launch has little to do with chemical propellants. Rocket propellants account for less than 1% of launch costs. The bulk of the cost is from the capital cost of rocket stages which get thrown away on each flight or (in the case of the Space Shuttle) maintenance labor.

    Capital and labor costs can be reduced with improved designs (fully reusable rockets). There is no need for antimatter, warp drive, etc. just to get into orbit. Exotic propulsion systems will merely increased the capital costs, which already predominate.

    • John Garrett

      January 6, 2013 at 7:46 pm

      This is a myth. Chemical rockets are among the most efficient engines ever designed.

      This is just plain incorrect. Ask yourself, why aren’t we using them to explore the outer solar system and nearby stars? The answer is because they’re vastly inefficient compared to the other technologies currently being developed. I think that’s the whole point of the article.

      You simply cannot use rocket engines to get you to our closest neighboring star in a reasonable time frame. It’s impossible. The article mentions “Carnot Limit“, I suggest you read up on it.

      • Kyle

        January 8, 2013 at 11:27 pm

        We’re not using them to explore the outer solar system because NOBODY WANTS TO PAY FOR IT. Space exploration ranks near the absolute bottom in America’s spending priorities, and we spend more money on it than the entire rest of the world combined. If NASA had even one-twentieth the budget of the Department of Defense, they could have colonized half the solar system by now.

        Who cares about nearby stars? Even if we got serious about it, it would us take centuries just to fully explore OUR OWN solar system. The rest of the galaxy can wait.

  4. Mike Smith

    March 1, 2013 at 5:56 am

    I think we have to ask the question “Why bother?” even i we had the money to pay for it.

    The nearest planet that could support life is over 10 light years away.

    We only have one planet. There is no “next season”. When we wreck it, we’re done.

    Lets use our time and energy toward saving this planet rather then engaging in useless space expeditions that will gain absolutely nothing except entertain some space scientists who never grew up.

    • Dominic

      April 4, 2013 at 4:52 pm

      Just don’t be a hippy please. If we can get more resources from other places, we wont have to be so dependent on our own. Yeah, I know we need to save our planet but there are things in this solar system that can greatly benefit us so I don’t appreciate you calling this all “useless”. These scientists are trying to expand our knowledge to benefit us in the future.

  5. Matt

    May 26, 2013 at 1:37 pm

    10^137 kilograms cannot be correct, that’s more than there is atoms in the observable universe.

  6. Kim E. Larsen

    May 26, 2013 at 5:19 pm

    All this talk about cost of fuel and using matter as propellant, it is just crazy when you think about it. To use chemical rocket fuel to convert to kinetic energy THEN which converts kinetic energy to potential energy (orbital height). That is lunacy!

    What we should do is find a more direct way to increase the potential energy, i.e. invent some sort of teleporter if possible. Tricky to do but I am convinced it is manageable given more research into that area. If successful we would have a very efficient and effective way to transport stuff.

  7. zeev

    May 26, 2013 at 7:22 pm

    The quality of comments in response to this article is low. One person cannot read well says something stupid, and ‘smart’ people reply thereby jumping into a trap.

    On top of this the article above is not about launching vehicles its about getting them from orbital space to deep space. Chemical launch rockets while amazing simply aren’t great for going to deep space out of earths orbit let alone mars.

    I’ll point out the article above missed one BIG technology that’s also experimental and quite real. Using magnetic sails which are essentially floating electromagnets that use gas pressure to create a large magnetosphere that creates drag in the solar wind. Directed ion beams could be used (mass beams) to push upon these sails at great distance even as the density of the solar wind breaks down farther from the sun.

    If I had my practical plan for a woreable engine I’d hookup a sizable nuclear battery to the existing top of the line ion engine. Id land this on an asteroid with a construction crew that drills the ion engine into the surface. Another machine goes around the polar opposite side of the asteroid and drills a tunnel through to the engine. The tunnel is then bored from the inside out and the asteroid ‘hollowed’ as its own mass is fed both to the ion engine as crushed particulate dust used as ionized mass for acceleration. Perhaps Phobos is the ideal asteroid to do this upon. It is already hollow and quite big. We could test the system to see if it is capable of slowing down Phobos into the orbit it will naturally achieve in 50 to 100 million years.

  8. bob

    May 29, 2013 at 1:10 pm

    It’s all about profit. For corporations profit > everything else, including our own survival, sadly. If we found mountains of diamonds on the moon, suddenly they would be tripping over each other to get some crappy old chemical rockets.

    • duda

      December 15, 2013 at 9:23 pm

      There has to be a reason to do anything. Doing something for profit boosts an economy. If someone is making money it means there is a service being provided or goods produced. Prices go down as a result and consumers benefit. Corporations should profit as much as possible for your own benefit.

      If we found diamonds on the moon the value of diamonds would drop to as low as it Costs to get the diamonds back to the buyers. In this case there would be any interest in bringing down costs to do so for the market. The result is diamond costs go down and so does space travel. Then those who mined diamonds in earth for a more expensive cost can go do something else more productive towards the economy.

      I love science. But when you’re taking about economics, science done for the sake of Science tanks an economy. Prices are driven up from funds dumped into something which may not have a use in society when those workers could have been doing something that is productive.

  9. JOHAN

    June 21, 2013 at 7:46 pm

    The way we humans are spoiling our world with digging up cutting down OUR resources without accountability, polluting OUR WATERS, OUR AIR and most of all KILLING other human beings. Do we go look for other planets to live on with the same people that are ruling the world today? I think not, but in my heart I hope I do get to see space travel in my time.

  10. Idi

    September 12, 2014 at 7:45 am

    For the next 100 years, it is more important to find a way to get into space than to go to another solar system. We should be concentrating on ways to achieve an efficient way of hitting escape velocity. Perhaps a rail gun to send non-living things into space.

  11. tchad49

    July 1, 2015 at 10:01 am

    Why is there not more interest in fission-fragment rocket propulsion? Paraphrasing from Wikipedia: nanoparticles of fissionable fuel are suspended in a vacuum chamber by an axial magnetic field (acting as a magnetic mirror) and an external electric field. This “dust” ionizes as fission occurs, keeping it suspended in the chamber. The incredibly high surface area of the particles makes radiative cooling simple. The axial magnetic field is too weak to affect the motions of the dust particles but strong enough to channel the fragments into a beam that can be (a) decelerated to provide power to the spacecraft and/or (b) emitted for thrust. “With exhaust velocities of 3%-5% the speed of light, and efficiencies up to 90%, the rocket should be able to achieve over 1,000,000s specific impulse.”

    Originally proposed here: Clark, R.; Sheldon, R. Dusty Plasma Based Fission Fragment Nuclear Reactor American Institute of Aeronautics and Astronautics. 15 April 2007.

  12. allessior

    March 8, 2016 at 6:37 pm

    The problem of continuity can be overcome if we exceed c in fast-transient bursts. So for example we achieve c, but then we do successive fast-transient bursts in such a way that “the trigger can never be pulled after the bullet hits the target”. That is, the trigger pulls occurs before contact and in the “valley” of each fast-transient.

    Given c=186,282.397mps, then define c as integral [0,delta] c+delta, where delta bursts at high acceleration between 0 and c.

    Basically, in small increments of bursts after achieving c, one can exceed c, without violating continuity.

    Once we do this we will be able to use actual ship movement through space and time in speeds that are on average in excess of c. This is an alternative to Warp Drive.

  13. Yj

    November 1, 2016 at 10:15 am

    70% of the speed of light? won’t that slow down time for the stuff inside the spacecraft, such that much more time will have passed when it comes back to Earth from its voyage?

  14. Hayden Smith

    December 15, 2016 at 11:26 am

    A fascinating subject, and a well-covered article – Thankyou! I acknowledge that higher-tech, higher cost, nuclear-pulse (bombs) may be the most effective way to embark on interstellar journeys. But, I still have a fascination with the lower-tech, lower cost, remote-pushed sail concept.

    One study on a microwave-pushed, mesh-sail design I encountered in the 1980s had a theoretical top speed of 50% light speed – a truly phenomenal figure! However, the best thing about sails, is also their Achilles Heel. Their wide cross section – as much as 1,000km in some schemes – makes them perfect push-targets for a Solar System based laser, for example. But, it also gives them a mightily big forward cross section too. The combined energy build up from “propulsion particles” from the back, and “drag particles” from the front, could be so much that the poor flimsy thing might ignite!

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