Slashdot Mirror
Using Fusion To Propel an Interstellar Probe
astroengine writes "We've heard of nuclear pulse propulsion being the ideal way to travel through interstellar space, but what would such a system look like? In the 1970's, the British Interstellar Society's (BIS) Project Daedalus was conceived to fire pellets of fusion fuel out the rear of an interstellar space probe that were ignited using a powerful laser system. The 'pulsed inertial confinement fusion' wouldn't be 'vastly different from a conventional internal combustion engine, where small droplets of gasoline are injected into a combustion chamber and ignited,' says Richard Obousy, Project Leader and Co-Founder of Project Icarus. Now, building on the knowledge of Daedalus, the researchers of Project Icarus have prepared a nifty animation of a fusion pulse propulsion system in operation on the original Daedalus vehicle."
http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion)">Project Orion from the 1950s
I really don't get the fascination with naming space projects after a failed attempt at flight. If there's one thing Icarus didn't do, it was "[build] on the knowledge of Daedalus!"
If you want a vision of the future, imagine a youtube comments section scrolling - forever.
Thanks to relativity / time dilation, you can get close w/o breaking it, and (at least to the passengers), it'll seem like a lot less time overall. Still more than four years to the nearest neighbor, but a lot less than the monster number of years it would take as we see it.
Quo usque tandem abutere, Nimbus, patientia nostra?
And theoretically, you can get to 0.01c with solar sails. The original calculation is a bit screwy since it assumes a solar sail with mass including payload of 1 kg per square kilometer. But it ignores the effects of the Sun's gravity well. Acceleration deep in a gravity well and for which the vehicle escapes the gravity well results in more delta v than acceleration outside of a gravity well. This is called the Oberth effect. Further on down, someone cites a researcher who supposedly came up with a beryllium sail that could achieve 0.03c.
"Nukular" hysteria will kill it.
Remember when we launched Cassini with a radioisotope thermo-electric generator?
"OH GOD IT'S GOING TO SPLODE AND KILL EVERYONE!!!111ONE"
Every time I see shit like that, I want to slap people.
--
BMO
Well you just accelerate in the other direction to slow down. It takes almost as long to slow down as it did to get up to speed ('almost' because you are now lighter having lost some mass) so you need to start braking early, and in fact you may well spend half your trip accelerating and the other half decelerating.
And it's not as simple as 'send out probes while you fly past' either, otherwise your probes need to be able to decelerate from whatever speed you are doing down to a slow enough speed to land on / orbit the planet, which isn't easy if you are already going at any decent fraction of C. Using the planets gravity will help to some extent, but I think even that has its limits.
I found it a rather tedious video (the narrator could stand to speak at least twice as fast). But the propulsion system is never described in the movie Avatar, so he's just making a lot of assumptions. (I don't believe Alpha Centauri is ever mentioned by name either -- another assumption).
Either way he doesn't disprove anything: he sets up a strawman (his assumptions of how the Avatar starship worked) and knocks them down again. In the context of that strawman, he's right (at least, I assume so -- I skipped over a bunch of that video). But that's not to say there aren't other mechanisms for getting from here to there in reasonable (for some values of reasonable) time frames. Indeed there are, although they may be impractical for engineering or economic reasons, not scientific ones.
-- Alastair
40 years ago, the idea of triggering fusion with a laser seemed promising. That's what Lawrence Livermore's Nova laser was supposed to be for. But laser ignition didn't work as an energy source.
Maybe someday, but not yet.
http://en.wikipedia.org/wiki/NERVA
'NERVA demonstrated that nuclear thermal rocket engines were a feasible and reliable tool for space exploration, and at the end of 1968 SNPO certified that the latest NERVA engine, the NRX/XE, met the requirements for a manned Mars mission. Although NERVA engines were built and tested as much as possible with flight-certified components and the engine was deemed ready for integration into a spacecraft, much of the U.S. space program was cancelled by the Nixon Administration before a manned visit to Mars could take place. NERVA was considered by the AEC, SNPO and NASA to be a highly successful program; it met or exceeded its program goals. Its principal objective was to "establish a technology base for nuclear rocket engine systems to be utilized in the design and development of propulsion systems for space mission application".[1] Virtually all space mission plans that use nuclear thermal rockets use derivative designs from the NERVA NRX or Pewee.'
Since we can't actually build a fusion drive, this seems like a much more promising technology.
And they combine the knowledge from both Daedalus and Icarus, I'm guessing they'll call it Helios. Wild guess.
There is no -1 Disagree.
Unlikely, clouds of interstellar dust several light years across tend to get noticed, especially if they're that close.
I may agree with what you say, but I will defend to the death your right to face the consequences of saying it.
Soapbox youtube videos are meant for people with a greater attention span than I have. Let me know when the book version comes out.
They build a ship that can reach the nearest star in 100 years. Off it goes.
25 years later, they build a ship that can make the journey in 50 years. Off it goes.
74 and a half years later, they build a ship that can make the journey in a day.
Hopefully there's no one in "suspended animation" or "space children" on the first two ships, otherwise they're gonna be pretty pissed off.
This is why getting people to commit to the effort to build an interstellar probe is pretty much a non-starter. We're perfectly happy to wait for the "breakthrough breakthrough" thankyouverymuch.
.
Prisencolinensinainciusol. Ol Rait!
Technical term for "propulsion achieved by firing pellets from the rear".
"Be nice, veer left, and never stop thinking" Iain Banks - Walking On Glass
The correct term is defecation.
even if we were to come up with some incredible propulsion breakthroughs, it still wouldn't help all that much. If Einstein was right, near light speed is as good as it gets. And that would still make all but our closest galactic neighbors practically inaccessible.
Space is vast and using conventional propulsion tech, you are correct.
But it also would be looking at a bird and saying we'll never fly. Technology can greatly affect what is 'possible'.
Einstein also agrees that worm holes are possible so faster than light travel *is* possible by his definition. You don't actually exceed the speed of light, but you get somewhere faster than the light would have by taking a shortcut.
Are we anywhere near that sort of ability? of course not. But so far it isn't impossible either.
People in cars cause accidents....accidents in cars cause people