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# Using Pulsars As GPS For Starships

#### timothy posted about a year ago | from the go-into-the-light-turn-left dept.

103

cold fjord writes with an excerpt from Science Codex: "CSIRO scientists have written software that could guide spacecraft to Alpha Centauri ... Dr George Hobbs (CSIRO) and his colleagues study pulsars — small spinning stars that deliver regular 'blips' or 'pulses' of radio waves and, sometimes, X-rays. Usually the astronomers are interested in measuring, very precisely, when the pulsar pulses arrive in the solar system. Slight deviations from the expected arrival times can give clues about the behaviour of a pulsar itself ... 'But we can also work backwards,' said Dr Hobbs. 'We can use information from pulsars to very precisely determine the position of our telescopes.' 'If the telescopes were on board a spacecraft, then we could get the position of the spacecraft.' Observations of at least four pulsars, every seven days, would be required. ... A paper (paywalled) describing in detail how the system would work has been accepted for publication by the journal Advances in Space Research." (Here is a related story from the same source.)

### Paywalled? (2, Interesting)

#### Anonymous Coward | about a year ago | (#44675161)

My taxes paid for it!

### Re:Paywalled? (4, Informative)

#### bartron (772079) | about a year ago | (#44675197)

Only partially. CSIRO gets some funding from the government but the rest it needs to make up from revenue by selling stuff (IP or services), setting up research partnerships etc.

### Re:Paywalled? (1)

#### citizenr (871508) | about a year ago | (#44675593)

So his taxes paid for salaries that provide those IP or services ...

### Re:Paywalled? (1)

#### Shienarier (185368) | about a year ago | (#44675679)

As stated, only partially.

### Re:Paywalled? (1)

#### NatasRevol (731260) | about a year ago | (#44676047)

I WANT EVERY FOURTH WORD!

Am I doing this right?

Also, filter error.

### Re:Paywalled? (0)

#### Anonymous Coward | about a year ago | (#44675245)

Are you Australian?

### Unpaywalled (5, Informative)

#### Anonymous Coward | about a year ago | (#44675165)

The paper is available free from the arXiv (http://arxiv.org/abs/1307.5375)

### Re:Unpaywalled (0)

#### Anonymous Coward | about a year ago | (#44677743)

lol. What a bunch of BS, I dreamed up this idea and posted it on one of those UFO chaser forums about John Titor almost a decade ago. Pretty bad when "real scientists" are ripping off ideas from the lunatic fringe boards. :D

### Re:Unpaywalled (0)

#### Anonymous Coward | about a year ago | (#44678397)

Did your post pick out specific pulsars and a specific trip, and working out the quantitative accuracy and errors for such a trip using parameters from a recently tested x-ray telescope?

I also assume that you read the article, replying to the link above, unlike everyone else who is complaining this idea is new the scientists ripped it off. So you would have seen that the authors of the paper make it quite clear the idea has been around decades, in quantitative form, from their citations and the fact they spend two pages talking about past work and the pros and cons to different approaches.

### Re:Unpaywalled (0)

#### Anonymous Coward | about a year ago | (#44678927)

The software they use for pulsar timing is open-source, too: http://sourceforge.net/projects/tempo2/ [sourceforge.net]

#### Anonymous Coward | about a year ago | (#44675175)

Full speed ahead to Goat Island!

#### Anonymous Coward | about a year ago | (#44675215)

Since this is about space travel, I think you mean "Goat Star". Sounds closer anyway. I wonder if that is the origin of the space goat that was threatening to eat Golgafrincham. ;-)

### The past called.. (5, Insightful)

#### sjwt (161428) | about a year ago | (#44675207)

This is so 1970's...

http://en.wikipedia.org/wiki/Pioneer_plaque [wikipedia.org]

### Re:The past called.. (2)

#### drinkypoo (153816) | about a year ago | (#44675281)

It should not come as a surprise to anyone. That doesn't mean it shouldn't be here, only that the summary sucks. It should have something new and interesting in it.

It should be obvious to anyone who is familiar with both GPS and DtoA. Which should be all of you by now, goddamn it.

### Re:The past called.. (-1)

#### Anonymous Coward | about a year ago | (#44675309)

Given our Orwellian future of having all of our resources consumed by a bungling elite and the mob they ride to hold power through Socialist bread-and-circus entitlements, the past has a certain attraction to it. . .

### Re: The past called.. (1)

#### Anonymous Coward | about a year ago | (#44675415)

Because sick poor people dying from preventable diseases is the mark of a successful society. I know super geniuses like you think the developed world should be like Victorian Britain but luckily most places have progressed since then.

### Re: The past called.. (1)

#### tripleevenfall (1990004) | about a year ago | (#44675463)

I suppose that depends on what you think is "progress"

### Re: The past called.. (1)

#### c0lo (1497653) | about a year ago | (#44675811)

I suppose that depends on what you think is "progress"

I don't suppose the GP post had in mind MDR [wikipedia.org] bugs. Maybe the (real AD) 1984 was better than nowadays in this concern, but... thanks God we got out of their hair style.

(my point... feel free to mod OT: exemplifying the "that depends" - even when right, I find quite pretentiously stupid an "It depends" answer on its own - i.e. with no details on the "dependency variables". Even, "So... it has come to that" is more to-the-point).

### Re: The past called.. (1)

#### NatasRevol (731260) | about a year ago | (#44676065)

Also doubling the population, while curing those sick people, and using up all our resources is the mark of a great society!

### Re: The past called.. (0)

#### Anonymous Coward | about a year ago | (#44676677)

Because sick poor people dying from preventable diseases is the mark of a successful society.

A successful society is one where so many resources go into non-value-increasing government activities, that the number of poor people grows to such an alarming level that even more of that non-value-increasing government activity is the easily-sold solution.

### Re: The past called.. (0)

#### Anonymous Coward | about a year ago | (#44680663)

You see, you can see you're a lunatic right wing nut, when you think that only non-value-increasing government activities exist.

Have you stopped and looked in a souvenir store ever in your life? There is perhaps 1 useful item there (usually a bottle opener). The rest is literally tonnes of actual junk. Junk that was processed into that state from perfectly good raw materials. Junk that was processed into that state with perfectly usable energy. (and yes; I know once its on the wire its use it or lose it, but why put it on the wire to make junk in the first place).

Seriously; there is so much non-value-increasing shit, that if you completely wiped out all government entirely (including the useful shit) I am sure you wouldn't have made even 10% inroad into the amount of complete and utter waste that infects our societies (plural, because I doubt I am in your country).

### Re:The past called.. (5, Informative)

#### Anonymous Coward | about a year ago | (#44675329)

The abstract of the paper (unpaywalled version [arxiv.org] ) has a better summary.

We demonstrate how observations of pulsars can be used to help navigate a spacecraft travelling in the solar system. We make use of archival observations of millisecond pulsars from the Parkes radio telescope in order to demonstrate the effectiveness of the method and highlight issues, such as pulsar spin irregularities, which need to be accounted for. We show that observations of four millisecond pulsars every seven days using a realistic X-ray telescope on the spacecraft throughout a journey from Earth to Mars can lead to position determinations better than ~20 km and velocity measurements with a precision of ~0.1 m/s.

In other words, they're not just saying that it's a theoretical possibility. They're saying "this is the type of telescope you need", "this is how you have to process the data", and "this is how precisely you can measure your position". Next step, I guess, is building the hardware.

### Re:The past called.. (0)

#### Anonymous Coward | about a year ago | (#44676619)

In software engineering terms, these people have taken a vague proposal and written some proof-of-concept code. Next step is a formal specification and writing a good version for deployment.

### Re:The past called.. (1)

#### Anonymous Coward | about a year ago | (#44675475)

It should be obvious to anyone who is familiar with both GPS and DtoA. Which should be all of you by now, goddamn it.

I'm fully familiar with Decimal-to-ASCII, but I don't see how that helps.

### Re:The past called.. (1)

#### c0lo (1497653) | about a year ago | (#44675839)

It should be obvious to anyone who is familiar with both GPS and DtoA. Which should be all of you by now, goddamn it.

I'm fully familiar with Decimal-to-ASCII, but I don't see how that helps.

OGHIHA (Oh, God, How I Hate Acronyms!)

### Re:The past called.. (0)

#### Anonymous Coward | about a year ago | (#44675967)

The idea might not be a surprise, but the implementation is a little more trickier than GPS when you don't have control over the waveform, and can't encode a time signal into it, or make sure it is on some easy to filter carrier wave.

### Re:The past called.. (0)

#### Anonymous Coward | about a year ago | (#44677067)

Isn't that how CSIRO works? They've stuck together a bunch of shit that's already worked out and they're planning to charge royalties on space travel for the next 5000 years.

### Re:The past called.. (1)

#### cold fjord (826450) | about a year ago | (#44676791)

This is so 1970's...

http://en.wikipedia.org/wiki/Pioneer_plaque [wikipedia.org]

The Pioneer plaque showed the position of the Earth's solar system. It wasn't for human navigation on a moving space vessel. (Although in a sense the Earth is a moving space vessel.)

### Really? (1)

#### Anonymous Coward | about a year ago | (#44675217)

Sounds like the CSIRO have been reading 1980's era science fiction. Maybe even the chapter in the Star Trek: The Next Generation Technical Manual [http://en.wikipedia.org/wiki/Star_Trek:_The_Next_Generation_Technical_Manual] that describes this navigation technique. (3.12 Guidance and Navigation)

### 1980s? Try the '60s or '70s at least. (1)

#### sgtrock (191182) | about a year ago | (#44675791)

My dad had some "Best of" Analog and Astounding collections dating back to the mid-'50s. Those omnibus editions got me hooked on sci-fi at a very young age.

I remember reading more than one story out of those where using pulsars to determine a ship's current position was a key plot point. According to Wikipedia, the first pulsar was discovered in 1967. Given the intense interest that most sci-fi writers and readers had in astronomy, I would be very surprised if that information wasn't common knowledge within the community almost immediately.

### Re:Really? (2)

#### donscarletti (569232) | about a year ago | (#44676711)

Yeah, it's totally boring that these guys are now able to calculate the observer's position anywhere in the galaxy to within several metres and velocity to within less than a meter per second, something previously only imagined in the realm of sci-fi. Next thing you know they'll be building a working warp drive, holodeck, transporter or something else equally trite and unoriginal.

### Re:Really? (1)

#### roc97007 (608802) | about a year ago | (#44679153)

Yeah, it's totally boring that these guys are now able to calculate the observer's position anywhere in the galaxy to within several metres and velocity to within less than a meter per second, something previously only imagined in the realm of sci-fi. Next thing you know they'll be building a working warp drive, holodeck, transporter or something else equally trite and unoriginal.

Warp drive, transporter, all good. (Warp drive now considered theoretically possible, according to previous articles on Slashdot.) I have mixed feelings about the holodeck. We've already seen in other types of entertainment (cough-tv-cough) that people tend to immerse for longer and longer periods of time, eventually becoming a kind of meat-based houseplant. I'm concerned that a holodeck would accelerate the process.

Oliver's retort to Fermi's Paradox: A civilization progresses to the point where it invents television. Then it collapses.

### What did Dr Calvin have to say? (0)

#### Anonymous Coward | about a year ago | (#44675263)

I'm sure that would be more interesting.

### Galactic waterholes (0)

#### Anonymous Coward | about a year ago | (#44675271)

Pulsars are also where intelligent alien species of the galaxy hang out.

### Good work Dr Hobbs! (3, Funny)

#### monzie (729782) | about a year ago | (#44675293)

I'd like to congratulate Dr Hobbs and his team for inventing a navigation system for Starships. Now, I look forward to Zefram Cochrane [wikipedia.org] 's work on the Warp Drive getting completed!

### Global? (0)

#### Anonymous Coward | about a year ago | (#44675305)

I guess in this context "GPS" is "Galactic Positioning System."

### Re:Global? (2)

#### edxwelch (600979) | about a year ago | (#44676425)

Apple maps will still screw it up and show Alpha Centari in the Andromeda galaxy

### "GPS?" (0)

#### Anonymous Coward | about a year ago | (#44675315)

Really? To which globe are we referring? I suppose "UPS" is taken as an acronym, but still....

### Done a long time ago (1)

#### PvtVoid (1252388) | about a year ago | (#44675361)

The brass plaques on the Pioneer and Voyager spacecraft show the location of the Earth using a map of nearby pulsars [johnstonsarchive.net] .

### Re:Done a long time ago (1)

#### iggymanz (596061) | about a year ago | (#44676989)

Brass (copper/zinc)? or is it bronze(copper/tin), the popular literature says copper. On that copper is plated gold, and aluminum plated on the cover. over the aluminum is plated very pure U-238 so if the thing were ever found (which would be tens or hundreds of thousands of years from now) an alien civilization could measure the decay product ratio and determine when craft launched.

Hopefully, our descendents don't end up having to rue our decision and do the "Independence Day" thing

### ridiculous (2)

#### DragonTHC (208439) | about a year ago | (#44675405)

This is like Karl Benz figuring out road signs.

If we currently do not have a way to travel to the stars, then what does it matter how we find our way among them?

### Re:ridiculous (0, Funny)

#### Anonymous Coward | about a year ago | (#44675485)

This is like Karl Benz figuring out road signs.

If we currently do not have a way to travel to the stars, then what does it matter how we find our way among them?

Go back to living in your cave.

### Re:ridiculous (1)

#### PolygamousRanchKid (1290638) | about a year ago | (#44675511)

If we currently do not have a way to travel to the stars, then what does it matter how we find our way among them?

You'd need an excellent politician to be able to build ways to travel to the stars, not a scientist. As in:

"I'm a space flight engineer, Jim! Not a politician with space travel plans!"

### Re:ridiculous (0)

#### Anonymous Coward | about a year ago | (#44675717)

If we currently do not have a way to travel to the stars, then what does it matter how we find our way among them?

If we do not have a way to find our way among the stars, what does it matter if we have a way to travel to them?

We need to figure out both parts of the problem. It doesn't really matter which part we get first. In the meantime, this technique provides a nifty way to precisely navigate within the solar system.

### Re:ridiculous (1)

#### Thanshin (1188877) | about a year ago | (#44675833)

This is like Karl Benz figuring out road signs.

If we currently do not have a way to travel to the stars, then what does it matter how we find our way among them?

Knowing the position of artificial objects in space with great precision might be useful if you enter the realm of the unknown.

e.g.: Imagine we launch a number of solar satellites and the information they return about their position doesn't match with the position we're seeing them at. Maybe it's a problem with our equations.

Maybe some defects of space curvature are only observable over long distances but cancel each other perfectly so as to disallow us from detecting them by their impact on the light coming from distant objects.

Maybe those defects allow the discovery of the "picosecond space ripple" phenomenon, which we learn to harness to build ftl ships.

The point is that new instruments give new data, and new data is one of the roots of technological advance.

### Except this is useful for what we already have... (0)

#### Anonymous Coward | about a year ago | (#44676003)

The paper directly addresses this is useful for travel within the solar system or even on a trip to Mars, routes that we've already sent crafts through before. There are additional experiments that would benefit from better positioning of satellites within the solar system.

### Re:Except this is useful for what we already have. (1)

#### DragonTHC (208439) | about a year ago | (#44677473)

That would be great if pulsars were fixed points in space. But the universe is expanding, and so their position changes even for objects in our own solar system.

### Re:Except this is useful for what we already have. (0)

#### Anonymous Coward | about a year ago | (#44678309)

First off, the pulsars being discussed, including the example selection used in the paper, are within our own galaxy and not that far away, so the expansion of the universe is not relevant (at least on any timescale that our solar system is still around). The methods are also rather insensitive to small movements of the pulsars, nonetheless, one of the prerequisites is that the pulsar be observed for a few years prior to the trip to establish timing and timing error. If you really insisted on using one with an obnoxious speed for a very long period, you could account for it, especially since the pulsars have to be monitored form Earth during the process too. But even if the pulsars were traveling some decent fraction of the speed of light, for short trips like to Mars, it wouldn't cause problems from their change in position.

### Too complicated (1, Interesting)

#### Sla$hPot (1189603) | about a year ago | (#44675441) Just add a cross hair to the "windscreen" of the space ship and point it at the damn star that you are going to pay a visit. There will be plenty of time for fine tuning. As a matter of fact, it would be a real good recreational job for the 10.000 year long trip. As the star got bigger you would simply change the velocity accordingly. Not such a big deal. I know, because i used to play Elite on a C64. ### Re:Too complicated (3, Insightful) #### Anonymous Coward | about a year ago | (#44675557) Stars move. You'd be adding hundreds of years to your travel time by taking a curved path. Better to go in a straight line to where the star will be in 10,000 years, for which purpose you'd need... navigation. ### Re:Too complicated (1) #### Sla$hPot (1189603) | about a year ago | (#44675929)

>Stars move. You'd be adding hundreds of years to your travel time by taking a curved path
You could bring a sniper to do the aiming.
Beside 100, plus minus compared to 100.000 years wouldn't be my biggest concern.

### Re:Too complicated (1)

#### TheCarp (96830) | about a year ago | (#44678109)

> You could bring a sniper to do the aiming.

You would have to take into account the one variable he doesn't... the speed of light. Even at distances where the curve and spin of the earth matter, the latency caused by light itself is not an issue.

Thing is, aiming at where the target will be is exactly what a sniper would tell you to do...that is what he does when leading a target.

Then you have to take into account another variable thats simpler for him: Fuel. Straight line accleration is easy, you just accelerate till you reach desired vector and then.... cruise until its time to slow down... course corrections take energy.

Likely you can't avoid some corrections over time, but, if you can minimize them up front, why wouldn't you? Especially when doing so just isn't that hard.

At least its not hard compared to.... figuring out your fuel requirements for both accelerating up to the required speed and then slowing back down: http://what-if.xkcd.com/58/ [xkcd.com]

This exponential increase is the central problem of rocketry: The fuel required to increase your speed by one km/s multiplies your weight by about 1.4. To get into orbit, you need to increase your speed to 8 km/s, which means you'll need a lot of fuel: $1.4\times1.4\times1.4\times1.4\times1.4\times1.4\times1.4\times1.4\approx 15$ times the original weight of your ship.

Using a rocket to slow down carries the same problem: Every 1 km/s decrease in speed multiplies your starting mass by that same factor of 1.4. If you want to slow all the way down to zeroâ"and drop gently into the atmosphereâ"the fuel requirements multiply your weight by 15 again.

Same problem.... but at a much larger scale and well.... if YOU want to try atmospheric braking at .9 c, I would like to observe that, from no closer than the nearest moon....

### Re:Too complicated (1)

#### Sla$hPot (1189603) | about a year ago | (#44678361) >You would have to take into account the one variable he doesn't... the speed of light. I just watched "The shooter" on Netflix yesterday. Lee Swagger would hit his target across the galaxy without any booster corrections, taking into account, the heat radiation, electromagnetic forces, space and time warping, gravity shearing, gravity pull from black matter, resistance from the microscopic amounts of hydrogen gas. Boom shaka laka. ### Re:Too complicated (1) #### GNious (953874) | about a year ago | (#44675585) I do something similar in Kerbal Space Program, when I get lazy during a rendevous maneuvre :) But, sometimes I do it "properly", and try to figure out what the funk a hofman transfer is, and where my target will be when I get to where it will have been... Pain the in the Rear! ### Re:Too complicated (1) #### gatkinso (15975) | about a year ago | (#44675599) You realize of course that stars are moving. ### Re:Too complicated (2) #### gatkinso (15975) | about a year ago | (#44675655) Yeah, aim for where Alpha Centauri was FOUR YEARS AGO... eventually you will be chasing the star and there is a good possibility it will be moving faster than you are so you will simply watch it recede from you as you slowly starve/suffocate. ### Re:Too complicated (1) #### alen (225700) | about a year ago | (#44675753) you know, we have these things called computers that can compensate and calculate the right answer ### Re:Too complicated (1) #### donscarletti (569232) | about a year ago | (#44676647) Yes, and you need telemetry to feed into the computer so it knows where you are and how fast you're going so it can calculate that answer, which is where TFA comes in. ### Re:Too complicated (1) #### deadweight (681827) | about a year ago | (#44676713) I have navigated a boat by the stars back in the day. It was a PITA because you can only see the stars and the horizon at once twice a day. So........I have a spacecraft with no clouds and no waves to screw up my sights. I can take angles between any two stars I want to 24/7 and feed the computer with the results. Seems good nav would be kind of easy. ### Re:Too complicated (1) #### iggymanz (596061) | about a year ago | (#44676919) sorry, but your view is too simplistic. You wish to end up in an orbit about interesting planet of the target star. No amount of pointing your craft at anything will get you the correct solution. ### Re:Too complicated (1) #### deadweight (681827) | about a year ago | (#44677479) No - your understanding of celestial navigation is a bit too simplistic. You don't "point" at a star. You measure angles between them. If the angle between star A and B is 30 degrees and B and C is 45 degrees and X and Y is 93 degrees and so on, there is only one place you can be and a computer can figure that out. ### Re:Too complicated (1) #### gatkinso (15975) | about a year ago | (#44677549) You know, they have these things called original posts that actually explain what the fuck is being discussed. ### Re:Too complicated (1) #### Sla$hPot (1189603) | about a year ago | (#44675881)

Then i would turn the ship around and go the other way around the galaxy and set the cryo-beds and the alarm clock for an other 250 million years, or what ever it takes for the galaxy to revolve.

good laugh

### Re:Too complicated (0)

#### Anonymous Coward | about a year ago | (#44679259)

Just add a cross hair to the "windscreen" of the space ship and point it at the damn star that you are going to pay a visit. There will be plenty of time for fine tuning. As a matter of fact, it would be a real good recreational job for the 10.000 year long trip. As the star got bigger you would simply change the velocity accordingly. Not such a big deal. I know, because i used to play Elite on a C64.

It's not complicated if you don't understand the problem. As other have pointed out, you don't go to the moon by firing a rocket pointed at the moon. If you're going to another star, you're pointing away from it the second half of your journey to slow down. You do want to stop there, right?

### Alpha Centauri is not where you 'see' it at (0)

#### Anonymous Coward | about a year ago | (#44675447)

Since light takes quite a few light years to arrive from distant locations, you will always arrive where it was if you point your fast star ship at it and travel to that location.

### Re:Alpha Centauri is not where you 'see' it at (0)

#### Anonymous Coward | about a year ago | (#44675711)

Don't discount alien pranksters screwing with us. Imagine.. "Those eartlings are at it again Xtentu, let's send them to the wrong star again. Flash a few more 'pulses' of radio waves at them then hit the X-ray beam a few times. Let's see how far off course they get this time before they figure it out"

### Second star to the right... (2)

#### phobos512 (766371) | about a year ago | (#44675491)

...and straight on 'till morning.

### Pioneer Pulsar Map (0)

#### Anonymous Coward | about a year ago | (#44675543)

Using pulsars for indicating coordinates has been done before - see for example the maps attached to the Pioneer spacecraft, which encode the location of the Sun in the galaxy:

http://en.wikipedia.org/wiki/Pioneer_plaque

### Oh cool (0)

#### Anonymous Coward | about a year ago | (#44675555)

Because it was the *software* holding us back!

### Visibility (2)

#### IPFreely (47576) | about a year ago | (#44675661)

Are the pulses from pulsars visible from all directions, or just from the plane of rotation? If you move far enough, will some disappear and others appear?

### Re:Visibility (3, Informative)

#### Anonymous Coward | about a year ago | (#44675799)

Are the pulses from pulsars visible from all directions, or just from the plane of rotation?

Not from all directions, but not always from the plane of rotation either. The pulse sweeps around at a fixed angle from the plane of rotation, which may not be 90 degrees.

But you're right: if we went far enough, we'd stop seeing some pulsars, and start seeing some new ones. So if we start travelling more than a thousand light years or so, we'll need another means of navigation.

The original paper [arxiv.org] only talks about using it as a means of navigation within the solar system, though, for which it's perfectly fine, and much more precise than existing methods.

### Re:Visibility (0)

#### Anonymous Coward | about a year ago | (#44680101)

Not from all directions, but not always from the plane of rotation either. The pulse sweeps around at a fixed angle from the plane of rotation, which may not be 90 degrees.

Not from all directions, but not always from the plane of rotation either. The pulse sweeps around at a fixed angle from the axis of rotation, which may not be 90 degrees.

(Sorry, typo.)

### Re:Visibility (0)

#### Anonymous Coward | about a year ago | (#44675989)

Are the pulses from pulsars visible from all directions, or just from the plane of rotation?
If you move far enough, will some disappear and others appear?

It is my understanding that this is true. But I'm sure that other astronomical phenomenon (like quasars) can fill in the gaps until new pulsars can be charted.

### Re:Visibility (0)

#### Anonymous Coward | about a year ago | (#44677967)

Quasars have absolutely nothing to do with celestial navigation. The word you're looking for is "stars".

### Re:Visibility (0)

#### Anonymous Coward | about a year ago | (#44676921)

"My answer in answering the question: "What does the red spectrum tell us about pulsars?" Write bigger. There are various words that need to be defined: what is a spectrum, what is a red one, why is it red, and why is it so frequently linked with pulsars? What the hell is a pulsar?"
-Rimmer [cervenytrpaslik.cz]
(quasars, I know)

### GPS??? (0)

#### Anonymous Coward | about a year ago | (#44675675)

I guess If you replace the word Global with Galactic then it would make sense.

### So what happens to the calibration if... (0)

#### Anonymous Coward | about a year ago | (#44675693)

What happens if we have a starquake on one of the pulsars thus shifting its rotational speed by a microsecond? Will our starship navigation put us off by a few parsecs?

### Acquiring Satellites (1)

#### Anonymous Coward | about a year ago | (#44675735)

Seven days to get a read on current position? Still better than NeverLost :)

### NASA Demo in the works (0)

#### Anonymous Coward | about a year ago | (#44675761)

NASA is developing an experiment called NICER/SEXTANT that will include a demonstration of this technique using x-ray pulsars. It will go on the ISS and use the pulsars to track the position of the ISS. Of course we have much better ways of doing that already but it could be an important demonstration for future probes to the outer solar system.

http://www.nasa.gov/topics/universe/features/zombie-stars.html

### X-Nav, been around a while, not yet practical (0)

#### Anonymous Coward | about a year ago | (#44675803)

The idea of using x-ray pulsars for navigation has been around for at least 10 years, probably longer. Wikipedia [http://en.wikipedia.org/wiki/X-ray_pulsar-based_navigation ] has some papers from MIT on it's stub entry.
Here's a presentation/paper from Naval Research Lab (NRL) in 2006 that gives you a general approach.

http://tycho.usno.navy.mil/IAU31/sheikh.pdf

And while it's nice to see demonstrations of software that show that it's doable, I don't think that's really the big challenge. The real challenge, and the one generally sort of hand-waved away, is that nobody has built a sufficiently useful X-ray telescope/detector that can be put on a spacecraft.

Sure folks say "look at Chandra which had 10s of tonnes of telescope, and modern X-ray telescopes in the lab at 10s of kilos", but it's a long long way from "lab bench" to "flying on a spacecraft", and not just because of the natural conservatism of spacecraft folks. Things on the bench have someone standing there to turn a knob, or tweak it to make it work today, etc. In space, it has to be really and truly maintenance free for years and years (particularly for deep space). When you come back and say "we've got a 1 kg X-ray telescope that has operated continuously with no manual intervention for 1 year", then I'll say "Yep, XNAV is here"

### Re:X-Nav, been around a while, not yet practical (0)

#### Anonymous Coward | about a year ago | (#44676045)

The paper used the parameters/observing ability of a real satellite for their estimates: Rossi X-ray Timing Explorer [wikipedia.org] . Sure, it is not a cubesat sized, but is smaller than Chandra.

### Only works (1)

#### rossdee (243626) | about a year ago | (#44675809)

If you're going slower than the speed of light

### Re:Only works (1)

#### iggymanz (596061) | about a year ago | (#44676863)

if you are going at the speed of light all events in time happen simultaneously

### Re:Only works (0)

#### Anonymous Coward | about a year ago | (#44677071)

And from your point of view the universe is a point, so you're everywhere at once... Or something like that.

### Nav Aids (1)

#### fast turtle (1118037) | about a year ago | (#44676353)

Pulsars: The Nav Beacon's of the Universe. Been that way since they were discovered - just like VOR beacons for Airports

### Talk about putting the cart before the horse! (1)

#### mark-t (151149) | about a year ago | (#44676371)

Working this out would be like people 3000 or so years ago trying to make some kinds of meaningful decisions about 21st century technology.

### Re:Talk about putting the cart before the horse! (2)

#### TeknoHog (164938) | about a year ago | (#44676843)

Developing a system of coordinates before you can actually travel - putting Descartes before the horse.

### Re:Talk about putting the cart before the horse! (0)

#### Anonymous Coward | about a year ago | (#44678421)

Except the paper uses data from an x-ray satellite that has already been launched and talks about a trajectory to Mars that is not particularly advanced or more difficult than previous trajectories we've used to get to Mars before...

### Re:Talk about putting the cart before the horse! (0)

#### Anonymous Coward | about a year ago | (#44682351)

Not at all. It's the best known method of navigation within our solar system.

### Trek thought of it (1)

#### operagost (62405) | about a year ago | (#44676555)

I seem to remember an episode of Star Trek where they ended up in the armpit of space such that they couldn't get a Federation navigation signal. They used pulsar triangulation to get a fix on their location.

Now, of course, implementation of this theory in the 21st century is a different matter!

### Re:Trek thought of it (0)

#### Anonymous Coward | about a year ago | (#44677491)

Was it Voyager, episode 1?

### Nothing New (0)

#### Anonymous Coward | about a year ago | (#44676637)

Pulsars and Cepheid Variables have been used as cosmic lighthouses for decades. These techniques are what have allowed astronomers to determine our relative position in the Universe, the structure of the Virgo cluster, and the general structure of the visible universe in general.

### Old hat for Minecraft fans... (1)

#### Gondola (189182) | about a year ago | (#44678293)

"Notch," the developer behind the famous Minecraft game, also ostensibly proposed pulsars as navigation beacons for his now-defunct game "0x10c." He used (generated) data collection from a pulsar as part of a series of puzzles related to PR for the game.

### CPS, not GPS (0)

#### Anonymous Coward | about a year ago | (#44679253)

Should be CPS for celestial positioning system, not GPS - it'll be a wee bit larger than global...

### Don't pulsars have a narrow emission beam? (1)

#### cyn1c77 (928549) | about a year ago | (#44680111)

I thought that pulsars emitted a beam of energy that was very narrow in angular size and located on a specific rotation axis.

What if you travel off the beam's axis while traveling large distances between astronomical objects?

### Re:Don't pulsars have a narrow emission beam? (0)

#### Anonymous Coward | about a year ago | (#44680713)

The width of a pulsar beam can be anywhere from a couple degrees to ~90 degrees depending on the conditions, with faster pulsars (like those that would be used in such a system) tending to be wider. The closest one used as an example in the paper was 500 light years away, even if the beam were just degrees across, that gives 17-18 light years of travel within the beam at this distance. The original paper was just concerned with travel within the solar system though.

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