Should we send interstellar probe to Alpha Centauri?

In summary: Using hydrogen bombs in space violates the Partial Test Ban Treaty.2. No one will use hydrogen bombs because...hey! we have these wonderful chemical rockets and flight times of hundres of thousands of years!3. Micrometeoroids with speeds of 10% of the speed of light.4. Very much fuel (hydrogen bombs) if the probe is to go into the orbit of the star(s)/planet.5. No one knows the orbit of the (hypothetical) planet.6. The probe and all its instruments should last at least 50 years without a human help.7. Radiation.8. Maybe the probe should have a very advanced Artificial Intelligence.
  • #1
Urvabara
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Should we send an interstellar (unmanned) probe to Alpha Centauri? Would it be much more expensive than a manned mission to Mars?

According to Wikipedia, velocities as high as 0.10c are possible with hydrogen bombs. That means that ~40 years flight time to the nearest star would be possible with today's technology!

There could be a Earth-like planet in the Alpha Centauri system so maybe the probe should try to go into the orbit of the planet and even land there.

How much would all this cost?

What problems there are?
I try to list here everything I know of:
1. Using hydrogen bombs in space violates the Partial Test Ban Treaty.
2. No one will use hydrogen bombs because...hey! we have these wonderful chemical rockets and flight times of hundres of thousands of years!
3. Micrometeoroids with speeds of 10% of the speed of light.
4. Very much fuel (hydrogen bombs) if the probe is to go into the orbit of the star(s)/planet.
5. No one knows the orbit of the (hypothetical) planet.
6. The probe and all its instruments should last at least 50 years without a human help.
7. Radiation.
8. Maybe the probe should have a very advanced Artificial Intelligence.

See also:

PS. A wise man once said: "Space, the final frontier. These are the voyages ... to explore strange new worlds. To seek out new life and new civilizations. To boldly go where no one has gone before." I do not recall who he was but I know he has done a good job in space exploration.
 
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  • #2
First of all, you do know that Star Trek was a TV show that had zero to do with real exploration...right?

The big thing I see as an issue is that, even if we did get a probe there, you are still looking at a 4+ year turn around time for all data transmitted from there (assuming nothing gets lost in the trip due to whatever problems might arise).
 
  • #3
Considering the speculative nature of ALL of the technolgies you mentioned, it is impossible to gauge feasability, cost, or "worth."

Your quoting of Star Trek tells me you have no basis in reality as to guessing what would be possible. At this point you might as well aim for building the Enterprise, you'll get just as far, which is to say, nowhere.
 
  • #4
FredGarvin said:
The big thing I see as an issue is that, even if we did get a probe there, you are still looking at a 4+ year turn around time for all data transmitted from there (assuming nothing gets lost in the trip due to whatever problems might arise).

OK, this is true, we will be looking at old data, but I would not see this as a big problem. Or are you concerned that we would not have any means to control the probe from Earth due to the time delay ? Surely it would really need some good AI so that it can make completely autonomous decisions.

But your point reminds me of another issue: How the probe should communicate its data to us. The strength of any radio signal goes down with 1 / R^2 and the NASA guys already had to use a lot of brain power to receive the Pioneer and Voyager signals.

But if I had to guess the worst problem, I would go for the protection of the probe against impact. (Urvabara's point 3) Even a small dust grain can ruin your day when it hits you with 30000 km / s ...
 
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  • #5
Mech_Engineer said:
Considering the speculative nature of ALL of the technolgies you mentioned, it is impossible to gauge feasability, cost, or "worth."

Your quoting of Star Trek tells me you have no basis in reality as to guessing what would be possible. At this point you might as well aim for building the Enterprise, you'll get just as far, which is to say, nowhere.

Even if he could not make it fly, the Enterprise might look pretty cool in his backyard :biggrin:
 
  • #6
Mech_Engineer said:
Your quoting of Star Trek tells me you have no basis in reality as to guessing what would be possible. At this point you might as well aim for building the Enterprise, you'll get just as far, which is to say, nowhere.

Umm? The quote was just a joke. No sense of humor, eh?

At least, I am trying to list all the problems and find a solution.
 
  • #7
FredGarvin said:
First of all, you do know that Star Trek was a TV show that had zero to do with real exploration...right?

Of course. Why else would I try to find all the problems and their solutions?

Saying that "this can't be done, because it hasn't be done before" doesn't get us anywhere and I strongly wonder why people so pessimistic even are scientists/engineers...

FredGarvin said:
The big thing I see as an issue is that, even if we did get a probe there, you are still looking at a 4+ year turn around time for all data transmitted from there (assuming nothing gets lost in the trip due to whatever problems might arise).

Of course the probe should be automatic but how much automatic/intelligent it must be, I don't know. I also wonder how much data is possible to send lightyears away: 1 bit/s? 1 kbit/s? 1 Mbit/s? 10 Mbit/s?
 
  • #8
Oberst Villa said:
Even if he could not make it fly, the Enterprise might look pretty cool in his backyard :biggrin:

Did you read this? It's NASA's paper. I am not the only one daydreming of interstellar probes. Even NASA's intelligent engineers are daydreaming of them. Did you read the timeframe of the Project Longshot? The paper was written in 1987 and 1988 and the paper basically says "all the problems could be solved withing the next 20 to 30 years." 20 years has already passed. Longshot probe was to be built at the Space Station Alpha, at least according to the Wikipedia. ISS is the Space Station Alpha after major budget cuts. If SSA was to be still in the orbit when sending the Longshot probe, I would assume that Longshot would be constructed during the early 2000s, maybe before 2020s.
 
  • #9
You're asking a bunch of engineers and scientists to judge the feasability of sending the first ever interstellar probe to Alpha Centauri using experimental and/or theroetical technologies that are decades if not centuries away from being considered viable, controlled by an all-encompassing AI system that adapts to problems that can't even be forseen.

What kind of a response were you hoping for? Engineers by nature are skeptical realists.
 
  • #10
Keep in mind that I am talking about unmanned probes so we don't have to worry about human lives. Of course, if the probe costs dozens of billions of dollars and the flight time is well over 50 years, it may not be very sensible to even send it.

Just my two eurocents.
 
  • #11
Urvabara said:
Saying that "this can't be done, because it hasn't be done before" doesn't get us anywhere and I strongly wonder why people so pessimistic even are scientists/engineers...

Nobody's saying it can't be done, they're saying it's too far in the future to consider with today's technology. i.e. it's still just science fiction.

Considering the difficulty of getting a probe to Mars (historically, a 50% failure rate), a journey that is 100 thousand times longer may be a bit ambitious.
 
  • #12
DaveC426913 said:
Nobody's saying it can't be done, they're saying it's too far in the future to consider with today's technology. i.e. it's still just science fiction.

That is why I try to concentrate on today's technology like hydrogen bombs (I am almost 100% sure that H-bombs work). I am not considering controlled fusion reactions, antimatter, wormholes, solar sails, laser sails or what ever, because they do not work yet. H-bombs should work. Why cannot they just try to use them? We do not need to reach the stars at the first try. If a small probe could be sent to the outer regions of the Solar system using H-bombs, it would be a major milestone.

DaveC426913 said:
Considering the difficulty of getting a probe to Mars (historically, a 50% failure rate), a journey that is 100 thousand times longer may be a bit ambitious.

Landing is usually the most difficult part of a probe mission. The interstellar probe probably wouldn't even land anywhere. For example, Project Daedalus is a (hypothetical) fly-by mission to the Barnard's Star.
 
  • #13
Urvabara said:
Did you read this? It's NASA's paper. I am not the only one daydreming of interstellar probes. Even NASA's intelligent engineers are daydreaming of them. Did you read the timeframe of the Project Longshot? The paper was written in 1987 and 1988 and the paper basically says "all the problems could be solved withing the next 20 to 30 years." 20 years has already passed. Longshot probe was to be built at the Space Station Alpha, at least according to the Wikipedia. ISS is the Space Station Alpha after major budget cuts. If SSA was to be still in the orbit when sending the Longshot probe, I would assume that Longshot would be constructed during the early 2000s, maybe before 2020s.

I did not intent to insult you with my remark about building the Enterprise in your backyard, apologies if I did. There is nothing wrong with getting inspiration from SciFi. In fact, I have stolen my name (Oberst Villa) from a character in a German SciFi movie (much cooler than Startrek I must say :cool:)

I am not very impressed by statements like "could be solved within 30 years". I recently read an article about rail-gun development from the 1980s (when Reagan's SDI had renewed interest in this things). In this review a paper from the early 1940s was cited, where a german scientist had been quite optimistic about rail-gun development if only the 3rd Reich would give him enough ressources for his research. Then, again in the 1980s article, much optimism for the next decades. Now we have 2008 and the only operational rail-gun I ever saw was in an Arnold Schwarzenegger movie ! (I know some guys built various prototypes in their labs, but the predictions were about operational guns.) So much for "can be solved within x0 years".

EDIT: P.S: If you read my post #4 you can see that I have been thinking about the feasibility of your idea quite seriously.
 
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  • #14
Oberst Villa said:
I did not intent to insult you with my remark about building the Enterprise in your backyard, apologies if I did. There is nothing wrong with getting inspiration from SciFi. In fact, I have stolen my name (Oberst Villa) from a character in a German SciFi movie (much cooler than Startrek I must say :cool:)

No hard feelings here. I am just always optimistic when I see a real scientific paper and their proposals and timelines and then I get sad when I see that those things are still far in the future: "Is this not going to happen in my lifetime?!"

I like Star Wars, Star Trek, The Space Odyssey, but still more I like science FACT. I like to read physics texts far more than popular science books. I want to get things right and I want to know every little detail behind things. (I am almost a Master of Science in Physics, btw. :)

Oberst Villa said:
EDIT: P.S: If you read my post #4 you can see that I have been thinking about the feasibility of your idea quite seriously.

Yes, thank you.
 
  • #15
Urvabara said:
I also wonder how much data is possible to send lightyears away: 1 bit/s? 1 kbit/s? 1 Mbit/s? 10 Mbit/s?

Among other things this depends on the size of the antenna on the probe (larger size => more gain) and the power of the transmitter. Neither comes for free in terms of mass. My guess is that even if with a really fat transmitter/antenna you should rather think of bits than Mbits per second. If the probe would go into an orbit this would not be much of a problem - waiting, say, one additional month for the data would not hurt much.
 
  • #16
If we are technically correct, there already are FIVE (5) interstellar probes:
Voyager 1
Voyager 2
New Horizons
Pioneer 10
Pioneer 11

It's just that they are too slow to get even outside the Solar system in a sensible time frame and we are losing the contact to them in the near future. Two (the Pioneers) of five are already non-functional.

Voyager 2: "Launch date August 20, 1977 (11286 days ago)." At least, it seems to be possible to build an interstellar probe that works 11286 days. :)
If the speed of the Voyager 2 would have been 0.10c, then it would be 3.1 lightyears away. Of course, it probably wouldn't be working at all because of the micrometeoroids and the radio signal's would be way too weak.
 
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  • #17
Oberst Villa said:
I am not very impressed by statements like "could be solved within 30 years". I recently read an article about rail-gun development from the 1980s (when Reagan's SDI had renewed interest in this things). In this review a paper from the early 1940s was cited, where a german scientist had been quite optimistic about rail-gun development if only the 3rd Reich would give him enough ressources for his research. Then, again in the 1980s article, much optimism for the next decades. Now we have 2008 and the only operational rail-gun I ever saw was in an Arnold Schwarzenegger movie ! (I know some guys built various prototypes in their labs, but the predictions were about operational guns.) So much for "can be solved within x0 years".
I saw operational railguns 20+ years ago (with muzzle velocities of 3 km/s), and the Navy is now testing one for naval artillery.

Here's a Popular Mechanics article on the BAE system delievered to the US Navy.
http://www.popularmechanics.com/technology/military_law/4231461.html [Broken]
 
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  • #18
Urvabara said:
That is why I try to concentrate on today's technology like hydrogen bombs (I am almost 100% sure that H-bombs work).
H-bombs work - as bombs. Their use as a drive mechanism is still sci-fi.[/QUOTE]

Urvabara said:
Landing is usually the most difficult part of a probe mission.
According to (my interpolation of) http://en.wikipedia.org/wiki/Exploration_of_Mars#Mars_Curse", only 3 out of 27 doomed Mars probes failed on landing. 16 failed somewhere between Earth orbit and Mars orbit.

It was dubbed the Mars Curse or the Galactic Ghoul.
 
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  • #19
Oberst Villa said:
I am not very impressed by statements like "could be solved within 30 years". I recently read an article about rail-gun development from the 1980s (when Reagan's SDI had renewed interest in this things). In this review a paper from the early 1940s was cited, where a german scientist had been quite optimistic about rail-gun development if only the 3rd Reich would give him enough ressources for his research. Then, again in the 1980s article, much optimism for the next decades. Now we have 2008 and the only operational rail-gun I ever saw was in an Arnold Schwarzenegger movie ! (I know some guys built various prototypes in their labs, but the predictions were about operational guns.) So much for "can be solved within x0 years".
Whether you are impressed or not, you have to realize that being technically able to do something means nothing in reality. There is a lot of other things that have to happen. This is where 99% of failed ventures get tripped up. We went to the moon not only because we had a lot of talented technical people, but mostly because Kennedy set the government on the path that it would be done and gave NASA the support they needed.

Like Asto pointed out, there is an operational rail gun being tested for the Navy.
 
  • #20
This is the engineering forum, so no one commented on this:
Urvabara said:
There could be a Earth-like planet in the Alpha Centauri system.
Extremely unlikely because:

a: If there was, we'd probably have detected it already.
b: It's a triple-star system so such a planet would probably not have a uniform/stable orbit.
Based on theoretical computer simulations, other planetary astronomers consider that any potential terrestrial planets that did once orbit near the stars' habitable zones are now likely no longer located there. The loss several billion years ago of these small bodies probably happened during the system's formation. All may have since been ejected by significant disruptions caused by strong gravitational or perturbation effects generated between the two main stellar components.
http://en.wikipedia.org/wiki/Alpha_Centauri

That's a lot of effort to answer a question that's already got a "probably not" answer.
 
  • #21
I wonder how we would react to a probe coming in
that was useing H-bombs to slow down
I think we need a better system before we try to explore
 
  • #22
ray b said:
I wonder how we would react to a probe coming in
that was useing H-bombs

"They're insane! We surrender!"
Footfall - Larry Niven
 
  • #23
DaveC426913 said:
According to Wiki, only 3 out of 27 (~10%) doomed Mars probes failed on landing. 16 (~60%) failed somewhere between Earth orbit and Mars orbit. The other 8 failed on launch (~30%).

It is called the Mars Curse.
I count at least six landing failures amongst the vehicles that were supposed to land.
  1. Mars 2. "Crash landed on surface of Mars".
  2. Mars 3. "Success (First successful landing)". That mission was a failure. It ceased transmission seconds after landing. The mission did not do any of the planned surface science, including use of its rovers, and only managed to transmit part of one rather useless picture of the Marse surface (low resolution and very low illumination).
  3. Mars 6. "Partial success". Partial success my ***. The Mars 6 lander mission ended with "direct proximity to the surface" at 61 m/s. Stripping away the bureaucrateze, Mars 6 ended with a crash landing.
  4. Mars Polar Lander. The most likely cause of the MPL failure was software interprations of vibrations that made the engines cut out 40 meters above the Martian surface.
  5. Deep Space 2. "The probes reached Mars apparently without incident, but communication was never established after landing."
  6. Beagle 2. "Lost contact while landing; Assumed to have crash landed".
I count 15 lander missions. Of those,
  • Two failed in the vicinity of Earth (Sputnik 24 and Mars 96).
  • One failed on route to Mars (Phobos 1).
  • One failed at Mars orbit insertion (Mars 7).
  • One failed at Mars entry (Phobos 2).
  • Six failed shortly before, at, or very shortly after landing (above).
  • Four succeeded (Viking 1, Viking 2, Pathfinder, Phoenix).
Landing failures accounts for six (seven if you count Phobos 2) out of the eleven failed lander missions.
 
  • #24
D H said:
I count at least six landing failures amongst the vehicles that were supposed to land.
  1. Mars 2. "Crash landed on surface of Mars".
  2. Mars 3. "Success (First successful landing)". That mission was a failure. It ceased transmission seconds after landing. The mission did not do any of the planned surface science, including use of its rovers, and only managed to transmit part of one rather useless picture of the Marse surface (low resolution and very low illumination).
  3. Mars 6. "Partial success". Partial success my ***. The Mars 6 lander mission ended with "direct proximity to the surface" at 61 m/s. Stripping away the bureaucrateze, Mars 6 ended with a crash landing.
  4. Mars Polar Lander. The most likely cause of the MPL failure was software interprations of vibrations that made the engines cut out 40 meters above the Martian surface.
  5. Deep Space 2. "The probes reached Mars apparently without incident, but communication was never established after landing."
  6. Beagle 2. "Lost contact while landing; Assumed to have crash landed".
I count 15 lander missions. Of those,
  • Two failed in the vicinity of Earth (Sputnik 24 and Mars 96).
  • One failed on route to Mars (Phobos 1).
  • One failed at Mars orbit insertion (Mars 7).
  • One failed at Mars entry (Phobos 2).
  • Six failed shortly before, at, or very shortly after landing (above).
  • Four succeeded (Viking 1, Viking 2, Pathfinder, Phoenix).
Landing failures accounts for six (seven if you count Phobos 2) out of the eleven failed lander missions.
OK, you've interpreted them differently and divided them up differently. For example: MPL "lost contact before arriving". In my books, that's an "en route" failure, not a "landing" failure. It failed before successfully achieving orbit.


Regardless, your results miss the point: you're only counting lander attempts. All lander attempts on either Mars or A. Centauri must first get there - which means you include the en route failures too.

I am trying to point out that landing is a relatively minor problem in the scope of long missions. The bigger problem is just getting there in the first place.


Or put another way: If 98 out of 100 men died crossing the desert, and one of the two remaining died by drinking from a poisoned well, would you be claiming that 50% of the failed desert crossings were due to poisoned water? :wink:
 
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  • #25
DaveC426913 said:
OK, you've interpreted them differently and divided them up differently. For example: MPL "lost contact before arriving". In my books, that's an "en route" failure, not a "landing" failure. It failed before successfully achieving orbit.
That is not what the accident review board said.
From http://oig.nasa.gov/old/inspections_assessments/MPL.pdf [Broken],
Office of Inspector General said:
The MPL's three landing legs were kept in a stowed position during launch and the spacecraft s journey to Mars. They were designed to deploy into position for landing when the MPL had descended to 1,500 meters above the surface of Mars. Each leg had a magnetic sensor to detect when it touched the planet s surface. When the sensors detected touchdown, the flight software would send a signal to shut down the MPL s thrusters. During MPL development, tests of the landing legs found that the magnetic sensors usually generated a false touchdown signal when the legs were deployed. To solve the problem, MPL systems requirements stated that all touchdown signals generated before the spacecraft descended to 40 meters above the surface should be ignored. However, the flight software requirements did not properly implement this system requirement. The result was that when the spacecraft descended to 40 meters above the surface, the touchdown signal from leg deployment was still in the system, causing the engine to shut off. At Mars, this would have resulted in the MPL hitting the surface at approximately 22 meters per second (50 mph), causing the loss of the spacecraft . Review teams have determined that this was the most probable cause of the loss of the MPL.
Regardless, your results miss the point: you're only counting lander attempts.
You're missing my point. Vehicles that aren't designed to land can't have landing failures. (They might have planetary impact failures, such as Mars Climate Observatory, but that is a different issue.)

I am trying to point out that landing is a minor problem in the scope of long missions. The bigger problem is just getting there in the first place.
That might well be the case for a mission to A. Centauri, but not for a mission to Mars. The vast majority of Mars flyby, orbiter, and lander mission failures occurred during active flight phases: launch, TMI, MOI, entry, descent, landing.

I've ignored the stuff about a mission to Alpha Centauri because, to be blunt, the concept is entirely ludicrous. A lander, doubly so.
 
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  • #26
D H said:
You're missing my point. Vehicles that aren't designed to land can't have landing failures.
I get that. But it is not the point.

The claim was that "the most dangerous part of a mission is the landing". I am refuting that claim. Landing or no, most missions have been lost in transit.
This is relevant to any long-term mission. Again, there's little point in worrying about landing issues if the craft never makes it there.

Again, you're concentrating on the poisoned well, and regarding the 98 dead men as immaterial to the mission success ratio.

D H said:
I've ignored the stuff about a mission to Alpha Centauri because, to be blunt, the concept is entirely ludicrous. A lander, doubly so.
Then you've ignored the intent of the post, meaning this is a derailment.
 
  • #27
DaveC426913 said:
Or put another way: If 98 out of 100 men died crossing the desert, and one of the two remaining died by drinking from a poisoned well, would you be claiming that 50% of the failed desert crossings were due to poisoned water?
That is not a good analogy for space mission failures. A better analogy: 100 men set off on a journey across a desert. Thirty three die drinking from a poisoned well at the start of the journey, another thirty three die drinking from a poisoned well at the end of the journey. Thirty three make it to the destination because only one dies while crossing the desert.

Nearly all of the problems with space missions occur at the start or at the end of the journey. Very few missions fail en route.

A mission to Alpha Centauri is a different beast. Assuming present-day technologies such a journey would take hundreds of years or more. In this case we would have to worry about things going wrong en route. The vehicle would have to expend a lot of energy just to stay warm and a would have to expend a whole lot of energy to communicate with Earth. The propulsion, avionics, communications, and sensors systems would have to be extremely redundant to accommodate the inevitable failures that would occur in such a long mission.

Assuming future technologies casts the problem into the realm of science fiction. This is the easy way out because it sweeps all of the hard problems under the rug.
 
  • #28
Ok. I just calculated that about 99.78% of the mass of the probe will be fuel, if assuming [tex]\Delta v = 29979245.8 + 29979245.8 = 59958491.6[/tex] m/s and maximum exhaust velocity of hydrogen nuke Orion of [tex]v_{e} = 9800000[/tex] m/s. That's a big fraction of fuel, I know...

Off topic. I also know you think I am crazy. Maybe I am but how about those who believe in ghosts, angels or god? I have never seen a scientific proves of the existence of super natural forces! I am just believing that engineers/scientists can overcome the problems of space exploration...
 
  • #29
Urvabara said:
Off topic. I also know you think I am crazy.
Nobody thinks you're crazy.
It's just that this forum mainly deals with present-day, established physics and technology, and tends not to deal with speculation so much.

Ok. I just calculated that about 99.78% of the mass of the probe will be fuel ...That's a big fraction of fuel, I know...
Oh I dunno, the Saturn V was 85% fuel by mass, and another 12% of launch mass was jettisoned just to deliver the remaining 3% payload to low orbit. That's only an order of magnitude diff (3% : .22%)

Urvabara said:
if assuming [tex]\Delta v = 29979245.8 + 29979245.8 = 59958491.6[/tex] m/s and maximum exhaust velocity of hydrogen nuke Orion of [tex]v_{e} = 9800000[/tex] m/s.
How did you calculate that? Are you assuming full thrust for the duration of the trip?
 
  • #30
DaveC426913 said:
How did you calculate that? Are you assuming full thrust for the duration of the trip?

I just used the Tsiolkovsky's rocket equation and put the numbers ([tex]\Delta v[/tex] and [tex]v_{e}[/tex]) in.

I don't know how long a time the accelerating takes exactly. If a = 10g = 98,1 m/s², then accelerating to 0.1c takes about 85 hours.

I think the magnitude of the fuel fraction maybe somewhat correct, but the exhaust velocity might be too optimistic. I took it from http://www.projectrho.com/rocket/rocket3c2.html.
 
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  • #31
ray b said:
I wonder how we would react to a probe coming in
that was useing H-bombs to slow down

My reaction would be: "So, there is a civilization that found a good use for their H-bomb stockpiles!"
 
  • #32
Astronuc said:
I saw operational railguns 20+ years ago (with muzzle velocities of 3 km/s), and the Navy is now testing one for naval artillery.

Here's a Popular Mechanics article on the BAE system delievered to the US Navy.
http://www.popularmechanics.com/technology/military_law/4231461.html [Broken]

First thing, thanks a lot for the link, I was not aware of this latest development, I have to admit that it makes my ranting a bit pointless.

As for the railguns that were operational 20+ years ago, probably I have communicated my thoughts quite badly. English is not my native language and I sometimes use words sloppily even in german. The heart of the problem seems to be my (possibly wrong) usage of the word "operational". What I had in my mind when saying that I have not seen an operational railgun yet was something like "a weapon system that is ready to be used in the field right now", (as opposed to a prototype in the lab). The best I could find in this context was a definition of "Initial Operational Capability", don't know whether it's an offical definition of this term, but anyway this is quite precisely what I meant:

"The first attainment of the capability to employ effectively a weapon, item of equipment, or system of approved specific characteristics, and which is manned or operated by an adequately trained, equipped, and supported military unit or force."

Now I have the impression that when YOU say "operational" you mean "something that works" (as opposed to something that is not working yet) and OK, this might just be the normal meaning of the word.

Anyway, maybe I should have said "I have not seen an operationally deployed railgun yet", then I could have avoided this misunderstanding, sorry for this.
 
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  • #33
FredGarvin said:
Whether you are impressed or not, you have to realize that being technically able to do something means nothing in reality. There is a lot of other things that have to happen. This is where 99% of failed ventures get tripped up. We went to the moon not only because we had a lot of talented technical people, but mostly because Kennedy set the government on the path that it would be done and gave NASA the support they needed.

Hmm, I don't disagree with you on this. But I think it's not very probable that such a foccussing of the nations scientific and industrial ressources on a single goal will be repeated in the near future. There is nobody in sight against whom the US would have to compete like they did against the Soviets.
 
  • #34
Urvabara said:
I don't know how long a time the accelerating takes exactly. If a = 10g = 98,1 m/s², then accelerating to 0.1c takes about 85 hours.

10g is muuuuuuuuch to high.

First thing, for the probe to tolerate such an acceleration without breaking apart, you would need a massive support structure, which would add a lot of mass to your probe => Kiss your 99,78% goodbye.

Second thing, there is no need for such a high acceleration. You need 40 years as a minimum, so would it hurt much to add e.g. 850 days for the acceleration phase ?
 
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  • #35
Urvabara said:
Ok. I just calculated that about 99.78% of the mass of the probe will be fuel, if assuming [tex]\Delta v = 29979245.8 + 29979245.8 = 59958491.6[/tex] m/s and maximum exhaust velocity of hydrogen nuke Orion of [tex]v_{e} = 9800000[/tex] m/s. That's a big fraction of fuel, I know...
An Orion-type rocket will need a *lot* of mass to protect the payload from the explosions.

Urvabara said:
I just used the Tsiolkovsky's rocket equation and put the numbers ([tex]\Delta v[/tex] and [tex]v_{e}[/tex]) in.
You are hypothesizing relativistic velocities, so you need to use the relativistic rocket equation:

[tex]\frac{\Delta v}{c} = \tanh\left(\frac {v_e}{c}\,\ln\frac {m_0}{m_1}\right)[/tex]

You chose an extremely unrealistic rocket. A more realistic choice of rocket technology will yield a very different mass ratio. For example, a VASIMR engine has an effective exhaust velocity of up to 300,000 m/s. The fuel mass ratio for a VASIMR engine is 99.999...%: 87 nines! There is no room for vehicle structure here. We need something a bit more exotic than VASIMR engine but something that has a ghost of a chance. How about injecting small amounts of antimatter into a plasma, forcing some plasma to escape at a high velocity, and just making a fly-by? Ths gets us down to 99.999...% fuel mass (13 nines). There's still no room for structure, but an improvement.

Note well that both of these rockets are way out there in terms of specific impulse. Nonetheless, neither a 200 fold or 600 fold increase in Isp will enable us to send a payload to Alpha Centauri.
 
<h2>1. What is the purpose of sending an interstellar probe to Alpha Centauri?</h2><p>The main purpose of sending an interstellar probe to Alpha Centauri is to explore and gather information about our closest neighboring star system. This could potentially lead to a better understanding of the universe and the possibility of finding habitable planets.</p><h2>2. How long would it take for the interstellar probe to reach Alpha Centauri?</h2><p>Based on current technology, it would take approximately 20-30 years for an interstellar probe to reach Alpha Centauri. This is due to the vast distance of 4.37 light years between our solar system and Alpha Centauri.</p><h2>3. What are the potential risks of sending an interstellar probe to Alpha Centauri?</h2><p>One of the main risks is the possibility of the probe encountering debris or other hazards during its journey. There is also the risk of technical malfunctions or failures, which could result in the loss of the probe. Additionally, there is the ethical concern of potentially contaminating any potential habitable planets in Alpha Centauri with Earth's microorganisms.</p><h2>4. How much would it cost to send an interstellar probe to Alpha Centauri?</h2><p>The cost of sending an interstellar probe to Alpha Centauri would depend on the specific mission design and technology used. However, it is estimated that such a mission could cost billions of dollars and would require significant funding and resources.</p><h2>5. What are the potential benefits of sending an interstellar probe to Alpha Centauri?</h2><p>Sending an interstellar probe to Alpha Centauri could lead to groundbreaking discoveries and advancements in our understanding of the universe. It could also pave the way for future interstellar missions and potentially even human exploration of other star systems. Additionally, the technology and knowledge gained from such a mission could have practical applications on Earth.</p>

1. What is the purpose of sending an interstellar probe to Alpha Centauri?

The main purpose of sending an interstellar probe to Alpha Centauri is to explore and gather information about our closest neighboring star system. This could potentially lead to a better understanding of the universe and the possibility of finding habitable planets.

2. How long would it take for the interstellar probe to reach Alpha Centauri?

Based on current technology, it would take approximately 20-30 years for an interstellar probe to reach Alpha Centauri. This is due to the vast distance of 4.37 light years between our solar system and Alpha Centauri.

3. What are the potential risks of sending an interstellar probe to Alpha Centauri?

One of the main risks is the possibility of the probe encountering debris or other hazards during its journey. There is also the risk of technical malfunctions or failures, which could result in the loss of the probe. Additionally, there is the ethical concern of potentially contaminating any potential habitable planets in Alpha Centauri with Earth's microorganisms.

4. How much would it cost to send an interstellar probe to Alpha Centauri?

The cost of sending an interstellar probe to Alpha Centauri would depend on the specific mission design and technology used. However, it is estimated that such a mission could cost billions of dollars and would require significant funding and resources.

5. What are the potential benefits of sending an interstellar probe to Alpha Centauri?

Sending an interstellar probe to Alpha Centauri could lead to groundbreaking discoveries and advancements in our understanding of the universe. It could also pave the way for future interstellar missions and potentially even human exploration of other star systems. Additionally, the technology and knowledge gained from such a mission could have practical applications on Earth.

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