Administrator
Some sobering news from a recent rocket science conference: It is highly improbable that humans will ever explore beyond the Solar System. This downbeat opinion comes from the Joint Propulsion Conference in Hartford, Connecticut, where future space propulsion challenges were discussed and debated. It is widely acknowledged that any form of interstellar travel would require [...]
More...
Established Member
Understandable. To me, it seems like the only way to achieve that would be the wrap drive trick itself. If only it were possible in our lifetime.
Established Member
I am stunned by the idea that propulsion scientists are so sure of themselves to make pronouncements ruling out future interstellar space travel. However, I think this conclusion will be falsified within 500-1000 years - if humanity survives and prospers.
These scientists should retire and allow a new generation to take over propulsion research who are not so jaded and depressed. They clearly have no faith in human potential. Very sad that this attitude of defeatism is pervasive in space propulsion circles.
Wrist-slitting all round folks
Order of Kilopi
Well, as the article did say, it could be done with little advance in technology if someone were still here 100,000 years later to hear back from the probe. It's a long time, but not quite "never".
Order of Kilopi
History is full of 'impossibilities' that have been broken. Peremptory terms like 'never' should not be employed by scientists. The only faith that´s left to this heart of stone is the faith in human inventiveness, and it looks clear to me that we´re going to find a way.
Order of Kilopi
Argos. Well said, and I agree. There are a few avenues yet untested. While SR considerations will always ban faster than light speeds...close to light speeds with some radiation shielding will work. This is an area I dabble in not lightly, and secrecy issues preclude an open forum discussion. It looks like the tides of fortune have recently swung in my favor though, and I may be able to devote some fulltime research to it and an entrepreneurial venture in the next few years. Peace. peteOriginally Posted by Argos
Established Member
In 2003 I presented a paper at that version of the Joint Propulsion Conference sponsored by these same folks at the NASA Marshall Space Flight Center in Huntsville, Al. and described a system to get to PC in less than 10 years (hyper-optimistic), 20 years based on medium optimism, and 40 years (a piece of cake). The conference organizers scheduled my presentation patronizingly in a not so popular room at a not so popular time. At that same conference a "particle sail" system was presented by Dana Andrews whom I do not know personally even though he lives in or near the same county as I here in Washington, U.S.A. My proposal and the times quoted above include the deceleration times and the establishing of an orbit around PC (or whichever AC star has been shown to be the most desirable. If an orbit is not desired the trip can be shorter but the end ellipse, if any, is indeterminable.
From the linked story:Thinking in terms of the energy of the entire planet is assigning yourself to much too small a box. We'll need big chunks of the sun's energy and not a small amount of the contents of Jupiter and/or Saturn. The system is massive and will take at least 300 years to develop to the point where the Interstellar Vehicle can initiate the trip from Earth geosynchronous orbit. The power will be supplied by a solar polar orbiting photon beam generator capable of beaming 10^16 to 10^18 watts to photovoltaic receivers which will supply powerful ion engines using linear particle accelerators fed from automatically controlled mass/charge discriminators thus allowing the power to be distributed as needed. Total exhaust rate will be held to 200 to 400 kg/second at as near light velocity as we can make the accelerators work.Using current technology would take tens of thousands of years, and even advanced concepts could take hundreds. But above all else, there is the question of fuel: How could a trip to Proxima Centauri be achieved if we'd need 100 times more energy than the entire planet currently generates?
Obviously neither this system nor any of its major components has been assembled nor tested and lessons learned therefrom will have to be applied as our experience matures. When it is tested I may have to back off from some of my optimism and/or include major modifications. Googling on "interstellar transportation" will provide a number schemes for interstellar transportation. None of the ones I read will work as well as my proposed system. In fact I'm not convinced any of the others will work at all unless they are very much like mine.
Administrator
The first of the three "Clarke's Laws":
When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.
Order of Kilopi
That´s great. I wish you all the success, trinitree.
Established Member
I'm sure that if we found an Earth-like planet around a Sun-like star, that we will send a conventional rocket with robots, telescopes and some microbs (just in case life hadn't arose there) right away!
Even if it takes 10 000 years to get there.
Banned
The article covered Current Conventional Means of travel.
This means: It did NOT cover possible futuristic technology.
So for those of you complaining that the scientists were doomsdayers, especially YOU Jetlack, try actually paying attention to what was discussed.
Established Member
Quoted for Truth.
You'd think these people would be familiar with the original Orion project, which could have produced a ship capable of making an interstellar flight at about 10% of lightspeed (though there was not nearly enough nuclear fuel at the time) in 1968.
The only reason it was never pursued was because of nuclear test and non-proliferation treaties. Obviously detonating a nuclear bomb or bombs for the purpose of lifting a craft into orbit is an unpopular idea. But it could be done, OR the craft could be assembled in orbit instead.
Member
How many times has some one said it cant be done. How long did it take us to jump from almost no technology 1860 to now 140 and were alreadyin space and have computers and items like that. In the next like say 40 years were proably going to have a bigger technology boom and possibly the "warp drive" or other forms of interstellar travel could be invented. We humans walk up to the edge of possible and walk right by it into the impossible.
Order of Kilopi
Argos. Thanks. peteThat´s great. I wish you all the success, trinitree.
Order of Kilopi
Here is hoping we do see interstellar travel.
Order of Kilopi
Maybe our efforts to not contaminate objects we explore are ill-advised. Perhaps we should be launching grossly contaminated projectiles out of the solar system, followed by viral version of our own DNA. They came from outta space: A doomed intelligent species desparate bid for immortality.
Established Member
what a drag.
drat's
Order of Kilopi
The point I think folks are missing is that getting to another star is not a simple step up from interplanetary travel, but is radically more difficult. And, if you're talking about more than a fly-by of the nearest stars beyond the sun, it becomes radically more difficult yet. Maybe we'll be able to manage that at some point, but if we do, we'll probably also be regularly using hundreds or thousands of times the Earth's current energy output.
It's debatable that there would ever be enough nuclear fuel for that. Orion is very inefficient if you're trying to get up to a significant fraction of lightspeed, and the ship (including the pusher plate) needs to survive quite a long time to accelerate that much. At best, you're talking about something that might be appropriate for an unmanned fly-by. After all, deceleration would increase the mass requirement greatly, and would require that the bombs would work properly after a minimum of several decades. Unfortunately, Orion also puts some minimum mass requirements on your space probe (you can only make bombs so small). It doesn't seem something that would be useful for a serious interstellar exploration program. For colonization, the mass requirements would be radically larger.
I say there is an invisible elf in my backyard. How do you prove that I am wrong?
The Leif Ericson Cruiser
Established Member
The conference article reminded me of a technical magazine article written many years ago - (late 1940s,) which unfortunately I cannot find; (so consider this anecdotal). The old article, using up-to-date technical knowledge of the time in terms of propulsion, engine design, rocketry and fuel consumption, came to the conclusion that a voyage to the moon and back was nearly impossible. The rocket required would have to be gigantic, nearly the size of a city and have enormous fictional power. The author as I recall made a case that the propulsion required to blast out of Earth orbit on a trajectory to intercept the moon would require power far beyond the capacity of any engines in the foreseeable future. The conclusion was that it would be nearly impossible.
Of course, they had no concept of payloads diminishing in size to equal the LEM lander that actually landed on the moon nearly 20 years later.
Yes, it seems impossible to ever travel to nearby stars but as Shakespeare put it in Hamlet: "There are more things in heaven and earth, Horatio, than are dreamt of in your philosophy."
In other words, we're so concerned with what is possible and impossible, and what real physics vs. science fiction is that we're not aware of a third alternative which encompasses practical but unthought-of applications. The not-yet-imagined seems too far from science fiction and too close to fairytale to be considered, but plans and schemes within its guise need not avoid pragmatic, practical engineering and physics problems as a basic framework. The scientist who wrote of the impossibility of lunar landings in the late 1940s was using sound data but was also not aware of the as yet unimagined applications that led to the Apollo program.
Order of Kilopi
I didn't take it as that. I took it as "It can't be done with physics as we know it. It's not a technological hurdle at this point; it's a science hurdle."
Doesn't mean a future discovery couldn't change everything; but that kind of physical break through is much less likely to happen any time soon than a mere advancement of technology.
Of course, current and budding minds should not give up. Onward and upward.
Established Member
Me too. What I read in the linked article didn't seem nearly as fatalistic as everyone's interpreting it to be. It was a bunch of guys saying, that right now it's looking like this will be very, very hard to achieve and there are some compelling practical reasons to believe that some of the technical or economic hurdles may turn out to be insurmountable. Which is is just a way of saying, "Maybe not," that manages to fill up 30 minutes of stage time in the conference auditorium. (I'm sure most of us have done something very similar in high school or college.)
There's a big difference between 'maybe not' and 'definitely not'.
Order of Kilopi
Uh, room wise don't we have at least two other Earths right here on Earth? (Hint: ocean floor)
Order of Kilopi
I've already claimed the ocean floor in the name of the nation Fazoria. Sorry.
Established Member
Current technology constrains the methods of powering interstellar transportation in the thinking of many advocates to processes using fusion, fission, sail, matter/anti-matter, particle beams, and photon beams or various combinations of these processes. Few advocates have taken the trouble to think through the details sufficiently to outline either the operational concept or the system level requirements to specify even in a broad general sense the energy and propellant mass (or equivalent alternatives) required to support trip times and the attendant vehicle velocities between specific stars. In most cases the infrastructure required to maintain the supplies of the means of maintaining the thrust sources across interstellar distances are not addressed. When they do, I think they will conclude, as I have, that a combination of a powerful photon beam received by the photovoltaic panels of the interstellar vehicle with ion engines exceeding terawatt capacity and thrust material laid down ahead of the vehicle by a paser particle beam is by far the better way to go.
In http://home.comcast.net/~mbmcneill7/ I attempt to address such issues, but I have been too optimistic about trip times. Here I want to discuss the constraints imposed by physics and solicit ideas for solutions that optimize the tradeoffs between propellant exhaust velocity (Ve) and the rate of propellant usage.
In order to accommodate the “fragility” of our currently most robust materials, I must lower the power density from a few megawatts per meter squared (achieving 10-year trips over 5 light years) incident on the vehicle power receiver to the “hundreds of kilowatts” level lengthening trip times to 30 years and beyond as shown in the table below.
common points of calculation Watts/
q Ve Years AU OV Meter^2
100 0.025 92 294297 25207 7251
200 0.0065 127.5 294234 25417 980
210 0.02 71 295940 55293 9744
4400 0.005 30.3 294851 29634 12758
1000 0.025 551.2 296200 45524 72509
99.92 0.0927 48 290277 21526 100016
2000 0.208 225 294189 33491 100336
[I see loss of table format has occurred on submittal]
The product of terms in the q and Ve columns (0.5 q*Ve^2) lead to the values in the watts/meter squared columns. Since I wish to have the vehicle assume orbit about the target star, after the vehicle travels the specified AU’s, the velocity is reduced to the values shown in the orbit velocity column and the number of years taken to arrive are listed in the years column. Vehicle masses for the various cases range from 6*10^9 kilograms to 36*10^12 kilograms with 99% of the mass allocated to the receiver. Propellant mass will be collected from the particles beamed from the trip initiating star. The target star system in this case is Alpha Centauri. This concept will not support trips longer than 5 light years maximum, thus restricting us to paths with stars so positioned with respect to each other unless we wish to install intermediate recollimation stations.
Order of Kilopi
The linked article does in fact mention the Orion Pulse rocket, but constrains it to about 5% of light speed, which sounds quite reasonable actually for that method. The supposedly more efficient Daedalus pulse rocket is based on technology that is at least partly speculative.
I read some of the comments on the article too; there's one from Stanton Freidman(!) who seems to have a rather inflated expectation of nuclear rocket technology.
Established Member
Following is a method: Credit to "Rails across the Galaxy" We build a human colony at the North and South pole of Mercury = one of the best locations in this solar system. We collect the 9 times stronger solar energy to power about a dozen lasers featuring very narrow beam at about one megawatt each. Perhaps 20 relay stations at asteroids between Venus and Mercury (Most will be out of range of the Mercury lasers occasionally) The asteroid lasers are similar and powered by laser beams plus sunlight. Dito for 19 lasers between Mercury and Earth orbit. Dito for 18 lasers between Venus and Earth orbit, Venus and Mars orbit Earth and asteroid belt orbit etc out to the Oort cloud = perhaps a million relay stations,total. Only a few kilowatts are available for the Oort cloud relay stations, but the technology will likely improve allowing more powerful lasers, and narrower beams. Solar sails can get a push from the lasers, at least part of the time, allowing faster than with only sunlight. Our interstellar probe is enrouue at perhaps 1% of the speed of light = 224 years to Centauri Proximal. It is improbable that the sail will be intact after 224 years, nor the subsystems functional, so our probe can't decelerate significantly as it zooms though the Centaur system, but lots of redundancy might allow the probe to return data to Earth, via laser beam and/or microwaves. Will anyone remember to listen with Arecibo or equivelent after almost 230 years? Neil
Last edited by neilzero; 2010-Jan-09 at 09:24 PM.
Established Member
Actualy, we could have intertellar travel in as little as 20 years, if stem cell research was allowed to progress to the point of life extension. with a 400-500 year life span, it would be quite possible to reach other star systems by confentional ion drives that might reach speeds in percentages of light.
So it takes 43 years to reach the Centari system at .1 light? Not a big deal when you'll live 400 to 500 years.
Personaly I thinks thats where our current focus should be, on extending our life spans such that interstellar travel at sub light speeds is practical.
Posting Permissions
Reply With Quote