Voyager 1 now EIGHTEEN LIGHT HOURS from home Something just a little bit remarkable happened last week. Launched on September 5th, 1977, Voyager 1 visited Jupiter in 1979 and Saturn 1980, sending back marvellous photos and data from both. The craft is not fitted with brakes and has been sailing out of the solar system since, most recently encountering a “roar” caused by …
... gives an average speed of 0.56 light minutes per week. Admittedly it wasn't travelling in a straight line for the first few years.
The path of the earth around the sun is about 52 light-minutes long. So if you are measuring the rate of increase of distance from earth to Voyager (as the tweet says), it could be boosted by up to 1 LMpw if the earth is moving away at the time.
It's interesting to note that 1 LMpw is almost exactly one ten-thousandth of the speed of light.
Just my 0.0001c.
I think acceleration would account for the speed difference. It's been traveling for 37 Years now so all the little pushes it gets from its thruster have added up. Plus all the planets and other large objects its passed by have also given it some pretty big pushes.
per NASA's Voyager facts page:
Launch date September 5, 1977Voyager 1 is ... now the most distant human-made object in the Universe and will continue to return important scientific data until its electrical power and thruster fuel are exhausted in 2020.
there's a list on the page of the scientific instruments aboard and what they were originally intended to do . . . they have adapted since then to explore interstellar space . . . not bad for a spacecraft "Built to last a mere five years"
all of our robot explorers should be built as well as the Voyagers (and Opportunity looks like it's carrying on the tradition).
Sometimes I wish NASA would get into building servers; whenever they build something it ends up lasting 10 times as long than designed. But when HP/Dell/IBM/Cisco/etc build something, it barely limps a few days beyond its warranty date...
Wheres the incentive to do that.... Much better that they get you to buy up new Kit every few years...
Where is the figure of three light minutes coming from? The two figures in the tweets are from consecutive days (2014:293 and 2014:294 which makes the time difference between one day of travel 8 seconds. (17:59:55 and 18:00:03) . This works out to 56 seconds a week.
It does sound too fast, 3 minutes/week is about 2.6 hours/year. Voyager does not hold much fuel, some for manoeuvring but little for propulsion and it's been over 30 years since it's last major encounter and it's met few bodies it could slingshot off so either it has accelerated somehow or it can't be going anything close to 3 minutes/week as that would put it about 60 hours out.
Kinda puts into context those plans about moving to another solar system.
It took two years to get to Jupiter.
30+ years later, it's still not hit one light-DAY away from us.
And the nearest star is, what, eight light-YEARS or something?
So it would be 365 * 8 * 30 years = 87,600 years before Voyager gets there with it's headstart.
Sure, it's not got a huge propulsion, but it makes you wonder how you intend to keep something powered and propulsive for decades or even centuries.
Honestly, we're kind trapped in the solar system. And we're even kind trapped on one planet at the moment. About time we took care of it, or started to get ways off it...
"It took two years to get to Jupiter.
30+ years later, it's still not hit one light-DAY away from us.
...
Sure, it's not got a huge propulsion, but it makes you wonder how you intend to keep something powered and propulsive for decades or even centuries."
But bear in mind it has 16 hydrazine thrusters and it's mission profile called for it to visit Jupiter and Saturn before cruising out of the solar system. The remaining fuel will be carefully rationed on maintaining it's attitude and pointing capability so that it can maintain comms with Earth until it's electrical power runs out - not frittered away on thrust such that the craft has electrical power but has no fuel to orient itself for transmission.
If your goal was inter-stellar travel, then consider that reaching 1% of c requires 85 hours at 1g. That would have you at 3000km/s - far faster than Voyager's 17km/s.
Heck, 1 day at 0.5g would get you to 423km/s, which makes Voyager's 17km/s look decidedly sedate.
Voyager 1 is not going quickly because it's a scientific mission who's job is to coast and see what it sees.
If you actually want to get somewhere, you could do it much, much faster.
The issue is less with fuelling it for decades as much as simply providing enough fuel mass to sustain the necessary acceleration burn (and corresponding deceleration burn at the far end).
This could certainly be done with low-mass craft like Voyager using existing high-specific-impulse ion technology.
It becomes more expensive and difficult when you scale to include life support for organics, etc. As you need a lot of power and a lot of fuel to accelerate those additional kilograms. A couple of planetary slingshots on the way out could help maximise speed relative to fuel consumption, but it wouldn't need to take decades to leave the solar system if you were in a hurry.
It doesn't change the fact however, that space is really, really big, and it would certainly take decades - if not centuries - to do 8 light years to our next nearest star (depending on the craft and mission profile). But not the thousands of millenia it would take Voyager 1.
"It doesn't change the fact however, that space is really, really big, and it would certainly take decades - if not centuries - to do 8 light years to our next nearest star"
It doesn't necessarily take that long for the crew. A constant 1g acceleration would get you to near c in 30 years; cruise for a bit with the engine off; then decelerate at 1g for 30 years. As time is hardly passing on board at all during the weightless period it is (a) not that uncomfortable and (b) you can travel almost as far as you want in a few hours.
So if we can crack the propulsion system, and the living and breeding in space problem, pretty much everywhere in the universe is only about 3 human generations away. Of course, the civilisation they've left behind might be long gone ...
"A constant 1g acceleration would get you to near "
But to get that constant acceleration the energy requirement increase rapidly as ->c
e.g rel. kinetic energy for 1 tonne at 0.9c & 0.999c compared with 'convention' kinetic energy
0.9 ~2E20 J ~3.6E19 J
0.999 ~2E21 J ~4.5E19 J
So an order of mag. increase of total energy required to go 0.9c -> 0.999c
A constant 1g acceleration would get you to near c in 30 years
There's something wrong with your maths.
v = at + u
v = final speed
a = acceleration
t = time
u = initial velocity
a = 1G = 9.80665 m/s^2
t = 1 year = 31,557,600 seconds
u =0
therefore v = 9.80665 x 31,557,600 = 309,474,338.04
Which is a tad more than 299,792,458 so is just not going to happen.
300 days at 1G would leave you zipping along at 254,188,368 m/s (84.8% c) and you'd cover 124 light days while doing it, as a fun side effect it'd also increase your mass to 1.886 times your rest mass.
Not all wrong though, 1 day at 0.5g would get you to 423km/s is correct. (423,647.28 m/s)
"There's something wrong with your maths."
Ah yes, *wipes egg from face*, looks like I should debug the old mental arithmetic unit again.
But I was interested in the idea that it gets harder and harder to accelerate because the mass of the craft increases - doesn't that just mean the mass of the propellant increases as well, so that the thrust stays constant?
doesn't that just mean the mass of the propellant increases as well, so that the thrust stays constant?
Good question, I wish I knew the answer but I would have thought that no matter what the mass of fuel is the volume is constant so the chemical or nuclear energy available remains constant. However reaction mass is a different question but as it's mass has increased it'll take more energy to propel a given volume so I don't think there's any easy way out of the problem.
As you get closer to c, your mass increases, so it gets harder and harder to accelerate.
If you got quickly to 0.8c, and took a 10 year journey to Alpha Centauri and back, you'd still be 6 years older on your return. (This is according to the Wikipedia page on "Twin Paradox")
But if you can maintain 1g of acceleration continuously for some tens of years, you could indeed get a long way:
https://en.wikipedia.org/wiki/Special_relativity
#How_far_can_one_travel_from_the_Earth.3F
"...if we can crack the propulsion system, and the living and breeding in space problem, pretty much everywhere in the universe is only about 3 human generations away. Of course, the civilisation they've left behind might be long gone..."
Congratulations, you've just outlined the premise of at least a dozen sci-fi movies, most notably Planet Of The Apes.
... and however well we look after it , it will still turn into either a smudge in the cloud of interstellar dust that results from the explosion of Sol, or a cold, lifeless marble orbiting a dead star.
Richest man in the graveyard much ?
The *only* chance that humankind has for a certain future is to get the hell out of Dodge, which means the Solar System itself.
...that one can surprise most people by stating that Voyager 1 is actually getting closer the Earth sometimes rather than farther all the time - while it's certainly whizzing away in normal terms, in a cosmic sense it's not moving all that fast, so whenever Earth is moving towards it in its orbit around the Sun, we handily outpace Voyager, briefly catching up a bit...
Unless there's a burn happening this does not compute
http://voyager.jpl.nasa.gov/mission/weekly-reports/
Isn't fully upto date but taking the data for the last couple of months Voyager 1 is moving away from the sun at around 10,000,000 km/per week. 10^9 m / 3^8ms-1 = 33s per wk or about 30 min per year which seems more in-line with what it has managed so far.
Proxima Centauri is 4.22 light-years away from us. Even if we could accelerate to 90% of C, that's still a long haul, especially with current life support technology. Alcubierre drive anyone? (not that we're likely to achieve one anytime soon)
http://en.wikipedia.org/wiki/Alcubierre_drive
It'll eventually slow to a stop without fuel, surely? Maybe they need to just have put bigger fuel tanks on it, ans as they won't weigh anything in space, it won't take any extra fuel to carry enormous quantities of space-diesel (or do they use Kerosene?).
"It'll need more fuel from somewhere "
There are so many misunderstandings about basic space physics in your post that you really need to read a basic primer.
Once it reached the solar system escape velocity nothing much will slow it down unless it runs into a rock. Bigger tanks mean bigger mass means lower acceleration. Weight at this point doesn't matter but mass does.
Voyager has taken 37 years to travel it's 18 light hours so far. So by quick head calculations, to travel it's full 1 light day distance is going to take another 12 (+ a few months) years. So It's not going to be able to broadcast it's done that light day before it's systems shutdown :-(
D
Note: Somehow I think I've got my maths very wrong, but I've now been working since Saturday with no sleep so excuse my school boy errors.
The calculations people are using seem to assume that Voyager has been travelling at a constant speed since launch.
In fact it spent a lot of time looping round the Solar System doing slingshots and stuff until its primary purposes were carried out and it was left to coast in a (more or less) straight line.
It seems reasonable to assume that it is now going faster than it has ever done, and it is this current speed that should be used in calculating its future position.
The Register 
Biting the hand that feeds IT
Copyright. All rights reserved © 1998–2025
