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Voyager 1 is about to reach one light-day from Earth

scienceclock.com

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Re: Voyager 1 is about to reach one light-day from Earth

#341

Post by noduerme »

Fargren wrote: post #339
noduerme wrote: post #337

Earlier quoted context omitted.

Could the probe just fire off some mass when it got there?

Any mass that it fires would have a starting velocity equal to that of the probe, and would need to be accelerated an equal velocity in the opposite direction. It would be a smaller mass, so it would require less fuel than decelerating the whole probe; but it's still a hard problem. Be careful with the word "just". It often makes something hard sound simple.

Not trying to oversimplify. But suppose 95% of the probe's mass was intended to be jettisoned ahead of it on arrival by an explosive charge, and would then serve as a reflector. That might give enough time for the probe to be captured by the star's gravity...?

Re: Voyager 1 is about to reach one light-day from Earth

#342

Post by brador »

omoikane wrote: post #81
glenstein wrote: post #30

Not that we would literally do this with Voyager, but it makes me wonder at the potential utility of a string of probes, one sent every couple of [insert correct time interval, decades, centuries?], to effectively create a communication relay stretching out into deep space somewhere. My understanding with the Voyagers 1 and 2 is (a) they will run out of power before they would ever get far enough to benefit from a re…

I wonder if we can go the reverse direction, where instead of launching more probes from Earth to serve as relays, the spacecraft would launch physical media toward Earth packed with whatever data it has collected. Given advancements in data storage density, we could achieve higher bandwidth than what's possible with radios. The logistics would be difficult since it involves catch those flying media, especially if th…

Binary encoding by pulsing the ion stream. Then picking that up with terrestrial telescopes. Very clever!

Re: Voyager 1 is about to reach one light-day from Earth

#343

Post by randerson »

Spare_account wrote: post #335
trhway wrote: post #299

Earlier quoted context omitted.

Sun as a focus lens. "Just" 500 AU. The Voyager can be overtaken in several years if we to launch today a probe with nuclear reactor powered ionic thruster - all the existing today tech - which can get to 100-200km/s in 2-3 stages (and if we stretch the technology a bit into tomorrow, we can get 10x that).

For anyone interested, this is approximately the wait/walk dilemma, specifically the interstellar travel subset: https://en.wikipedia.org/wiki/Wait/walk_dilemma#Interstellar... I was listening to an old edition of the Fraser Cain weekly question/answer podcast earlier where he described this exact thing. I think he said that someone has run the numbers in the context of human survivable travel to nearby stars and on…

I guess there's a paradox in that we'd only make the progress needed to overtake if we are still launching throughout those 600 years and iteratively improving and getting feedback along the way.

Because the alternative is everyone waiting on one big 600-year government project. Hard to imagine that going well. (And it has to be government, because no private company could raise funds with its potential payback centuries after the investors die. For that matter, I can't see a democratic government selling that to taxpayers for 150 straight election cycles either.)

Re: Voyager 1 is about to reach one light-day from Earth

#344

Post by 7952 »

bena wrote: post #129
Sanzig wrote: post #106

Earlier quoted context omitted.

Provided we don't wipe ourselves out, there's no technical reason why we can't go interstellar. It's just way harder and more energy intensive than most people imagine, so I doubt it's happening any time in the next few hundred years. But we already understand the physics and feasibility of "slow" (single-digit fractions of c ) interstellar propulsion systems. Nuclear pulse propulsion and fission fragment rockets req…

Yes, it's incredibly easy to do these things once you've done all these other, incredibly difficult things first. The furthest a human has been is 250k miles (far side of the moon). The fastest a human has traveled is only 0.0037% the speed of light. The ISS is about 260 miles from the Earth. At that height, the gravity is actually roughly the same as on the surface, it's only because it is in constant freefall that…

And once you have done those incredibly difficult things it is possible that the game changes entirely. A significant number of humans could live in space and have limited contact with planets.

Re: Voyager 1 is about to reach one light-day from Earth

#345

Post by ColinWright »

Too late for anyone to see this comment, and it's just a trivial bugbear of mine, but the article has this:

> "... meaning a radio signal will take a full 24 hours—a full light-day—to reach it."

They don't mean "a full light-day" ... they mean "a full day". They're talking about the time it will take, and "light-day" is the distance it's travelling.

A trivial type error that a compiler would barf on, that people will gloss over and not notice, but which niggles at me.

Sorry ... I now return you to your regular programming.

Re: Voyager 1 is about to reach one light-day from Earth

#346

Post by Sharlin »

namirez wrote: post #172
Sharlin wrote: post #17

Earlier quoted context omitted.

Voyager 2 was the real beneficiary of the rare outer planet alignment, as it went on the famous Grand Tour, visiting all four of the giants. It did gravity assists at Jupiter, Saturn, and Uranus. [1] shows the rough velocity of V2 over time. Voyager 1 was directed to perform a flyby of Titan, at the cost of being thrown out of the ecliptic and being unable to visit the ice giants like its sister. But this was deemed…

There isn’t much value in gravity assists from Uranus or Neptune since they move much more slowly than Jupiter and Saturn.

Yes, but the trajectory change was also needed at Uranus. It’s not only about magnitude, it’s also about direction :)

Re: Voyager 1 is about to reach one light-day from Earth

#347

Post by Spare_account »

randerson wrote: post #343
Spare_account wrote: post #335

Earlier quoted context omitted.

For anyone interested, this is approximately the wait/walk dilemma, specifically the interstellar travel subset: https://en.wikipedia.org/wiki/Wait/walk_dilemma#Interstellar... I was listening to an old edition of the Fraser Cain weekly question/answer podcast earlier where he described this exact thing. I think he said that someone has run the numbers in the context of human survivable travel to nearby stars and on…

I guess there's a paradox in that we'd only make the progress needed to overtake if we are still launching throughout those 600 years and iteratively improving and getting feedback along the way. Because the alternative is everyone waiting on one big 600-year government project. Hard to imagine that going well. (And it has to be government, because no private company could raise funds with its potential payback centu…

Yes, my understanding is that the 600 year figure was arrived at assuming that there is iterative progress in propulsion technology throughout the intervening years. But at the end of the day, it is just some number that some dude on YouTube said one time (although Fraser Cain is in fact not just some dude, he's a reliable space journalist (and you can take that from me, some dude on the Internet))

Re: Voyager 1 is about to reach one light-day from Earth

#348

Post by [deleted] »

glenstein wrote: post #30

Not that we would literally do this with Voyager, but it makes me wonder at the potential utility of a string of probes, one sent every couple of [insert correct time interval, decades, centuries?], to effectively create a communication relay stretching out into deep space somewhere. My understanding with the Voyagers 1 and 2 is (a) they will run out of power before they would ever get far enough to benefit from a re…

[deleted]

Re: Voyager 1 is about to reach one light-day from Earth

#349

Post by Fargren »

noduerme wrote: post #341
Fargren wrote: post #339

Earlier quoted context omitted.

Any mass that it fires would have a starting velocity equal to that of the probe, and would need to be accelerated an equal velocity in the opposite direction. It would be a smaller mass, so it would require less fuel than decelerating the whole probe; but it's still a hard problem. Be careful with the word "just". It often makes something hard sound simple.

Not trying to oversimplify. But suppose 95% of the probe's mass was intended to be jettisoned ahead of it on arrival by an explosive charge, and would then serve as a reflector. That might give enough time for the probe to be captured by the star's gravity...?

It seems to me that building a recording device that can survive in space, that it's very light, and that can not break apart after receiving the impact from an explosive charge strong enough to decelerate it from the speeds that would take it to Alpha Centauri is... maybe impossible.

We're talking about 0.2 light years. To reach it in 20 years, that's 1/10th of the speed of light. The forces to decelerate that are pretty high.

I did a quick napkin calculation (assuming the device weighs 1kg), that's close to 3000 kiloNewton, if it has 10 seconds to decelerate. The thrust of an F100 jet engine is around 130 kN.

IANan aerounatics engineer, so I could be totally wrong.

Re: Voyager 1 is about to reach one light-day from Earth

#350

Post by messe »

pjerem wrote: post #38
acec wrote: post #26

50 years for 1 light day... so to arrive Alpha Centauri that is 4.2 light years far away... 76549 years and 364 days :-)

Less than that is you are constantly accelerating.

Less than that if you're going faster too. What's your point?
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