Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Voyager 2’s Discoveries from Interstellar Space

nytimes.com

Post reply on HN
Print view View original

81–90 of 109 posts

Re: Voyager 2’s Discoveries from Interstellar Space

#81

Post by mixmastamyk »

mlthoughts2018 wrote: post #71
kolinko wrote: post #58

Earlier quoted context omitted.

Agile shares a lot in common with practices mentioned in „Mythical man-month”, which in turn was based on the good practices from the Voyager era. Also, extreme programming was based in part on the TDD from Mercury program, iirc. Having said that - yes, cargo cult agile sucks, we all know that.

The surgical team analogy at the core of TMMM is totally incongruent with agile principles. The book espouses a ton of anti-agile (small a) ideas.

Maybe, I know he highly recommended iterative development in the silver bullet essay: http://eppsnet.com/2006/06/respect-the-classics-man-no-silve...

Re: Voyager 2’s Discoveries from Interstellar Space

#82

Post by NotSammyHagar »

NovemberWhiskey wrote: post #76
outworlder wrote: post #54

Earlier quoted context omitted.

This is a fairly common trope in SciFi settings which have Generation Ships. Some time after the ship gets launched (centuries, even), FTL gets developed. Then they either arrive and find a civilization at their destination, or they are considered to be off-limits and not to be messed with, depending on the setting. That assumes such improvements are even possible. At least for non-magical propulsion, we don't really…

As in most cases, problems left for the reader are usually the hard ones! The rocket equation tells us that if one somehow managed to build a spacecraft containing an infinite power source that weighed a single kilogram, and incorporated the most efficient engine designs known to us (electrostatic ion thrusters), it would still need to be fueled with a reaction mass of xenon equivalent to approximately two billion ti…

Please add a little more info how this is calculated because my expectation is quite different.

Re: Voyager 2’s Discoveries from Interstellar Space

#83

Post by SenHeng »

skvj wrote: post #44

Here's a great illustration of Voyager 1 and Voyager 2 outside of the heliosphere: https://www.nasa.gov/press-release/nasa-s-voyager-2-probe-en...

Is there a reason why the left side of the heliosphere is so elongated?

Is it simply because we haven't sent any probes there and so don't really know where it ends or is it really this oblong shaped?

Re: Voyager 2’s Discoveries from Interstellar Space

#84

Post by brownbat »

iamcreasy wrote: post #65
outworlder wrote: post #46

Earlier quoted context omitted.

> Are they powered via PV Consider that light emitted from the Sun will decay with the square of the distance – as it is irradiated in all directions. To Voyager, the Sun looks like an ordinary star – although one much brighter than the others. Not much energy can be harvested there. Until recently, photovoltaics were useless as far away as Jupiter. Given the tech advancements, we can now use them there (and have). F…

> To Voyager, the Sun looks like an ordinary star – although one much brighter than the others. Not much energy can be harvested there. This blew my mind. Do you have a reference that talks more on this topic?

Not as far out as Voyager, but I enjoyed this series of depictions of the sun from each planet, which illustrates the general point:

https://www.iflscience.com/space/sun-looks-like-every-planet...

Re: Voyager 2’s Discoveries from Interstellar Space

#85

Post by trianglem »

NovemberWhiskey wrote: post #76
outworlder wrote: post #54

Earlier quoted context omitted.

This is a fairly common trope in SciFi settings which have Generation Ships. Some time after the ship gets launched (centuries, even), FTL gets developed. Then they either arrive and find a civilization at their destination, or they are considered to be off-limits and not to be messed with, depending on the setting. That assumes such improvements are even possible. At least for non-magical propulsion, we don't really…

As in most cases, problems left for the reader are usually the hard ones! The rocket equation tells us that if one somehow managed to build a spacecraft containing an infinite power source that weighed a single kilogram, and incorporated the most efficient engine designs known to us (electrostatic ion thrusters), it would still need to be fueled with a reaction mass of xenon equivalent to approximately two billion ti…

Wasn't project Orion about using successive nuclear explosions to get up to 25% the speed of light?

Re: Voyager 2’s Discoveries from Interstellar Space

#86

Post by ssijak »

flurdy wrote: post #12

I am always baffled by the conundrum of the futility of launching a spacecraft to go far away by our own ability to invent faster engines. Say it takes 300 years to get to Alpha Centauri. If you launch it you have 150 years to invent a spacecraft that goes twice the speed of the first one. Very likely. If you launch that one it will overtake the other one. Now you have 75 years to find an even faster engine. Launch i…

We cant reach it in a year because it is more than 4 light years away.

Re: Voyager 2’s Discoveries from Interstellar Space

#87

Post by petschge »

NotSammyHagar wrote: post #82
NovemberWhiskey wrote: post #76

Earlier quoted context omitted.

As in most cases, problems left for the reader are usually the hard ones! The rocket equation tells us that if one somehow managed to build a spacecraft containing an infinite power source that weighed a single kilogram, and incorporated the most efficient engine designs known to us (electrostatic ion thrusters), it would still need to be fueled with a reaction mass of xenon equivalent to approximately two billion ti…

Please add a little more info how this is calculated because my expectation is quite different.

The rocket equation is dv = isp * g0 * ln(m0/mf) [1]. For dv we assume 10% the speed of light, isp of a ion thruster is say 19300 s [2], for g0 I will use 9.80665m/s^2 and mf is 1kg. For m0 this gives us m0 = mf * exp(0.1 c / (isp*g0)) = 6.2e69 kg. The (baryonic mass) of the observable universe is something like 1.5e53 kg [3]. Or in other words about a factor 4e15 (much more than the 2e9 the grand parent poster claimed) less then the necessary fuel.

1: https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation 2: https://en.wikipedia.org/wiki/Ion_thruster#Comparisons 3: https://en.wikipedia.org/wiki/Observable_universe

Re: Voyager 2’s Discoveries from Interstellar Space

#88

Post by petschge »

SenHeng wrote: post #83
skvj wrote: post #44

Here's a great illustration of Voyager 1 and Voyager 2 outside of the heliosphere: https://www.nasa.gov/press-release/nasa-s-voyager-2-probe-en...

Is there a reason why the left side of the heliosphere is so elongated? Is it simply because we haven't sent any probes there and so don't really know where it ends or is it really this oblong shaped?

Because the solar system is moving relative to the local interstellar medium. So effectively you get a "headwind".

Re: Voyager 2’s Discoveries from Interstellar Space

#89

Post by sbmthakur »

Ductapemaster wrote: post #43
wyldfire wrote: post #36

Earlier quoted context omitted.

Are they powered via PV? IIRC one of them (satellite/probes) had some nuclear fuel.

Both Voyager 1 and 2 use RTG's (Radioisotope Thermoelectric Generators)[1] for power. Every year the RTG puts out less and less power, so instruments are gradually powered down to preserve the functionality of the critical ones for as long as possible. According to JPL[2] at least one scientific instrument will continue functioning until about 2025, and the crafts will remain in range of the Deep Space Network until…

Thanks for mentioning Deep Space Network. I didn't know this is a thing and is more than 50 years old.

https://deepspace.jpl.nasa.gov/about/

Re: Voyager 2’s Discoveries from Interstellar Space

#90

Post by samus »

Ductapemaster wrote: post #43
wyldfire wrote: post #36

Earlier quoted context omitted.

Are they powered via PV? IIRC one of them (satellite/probes) had some nuclear fuel.

Both Voyager 1 and 2 use RTG's (Radioisotope Thermoelectric Generators)[1] for power. Every year the RTG puts out less and less power, so instruments are gradually powered down to preserve the functionality of the critical ones for as long as possible. According to JPL[2] at least one scientific instrument will continue functioning until about 2025, and the crafts will remain in range of the Deep Space Network until…

Let's just hope the Deep Space Network will continue being funded. Further capsizing its budget and shutting it down would make it impossible to stay in contact with one of the greatest achievement of Mankind.
Post reply on HN