New Horizons: Nasa spacecraft speeds past Pluto • Hacker News Board

Re: New Horizons: Nasa spacecraft speeds past Pluto

#191

Post by biot » Tue, Jul 14, 2015, 5:48 PM UTC

ringshall wrote: post #101

Interesting note, as of today, the US is the first country to have successful spacecraft missions visit all of the classical planets. There is one big exception, of course: the Soviet Union was the first to have a spacecraft visit Earth, with Spunink. This category is completely arbitrary, especially given that Pluto is now considered a minor planet. Still, it's an achievement of note. Mercury - 1974, Mariner 10 Venu…

The Russians had some amazing firsts with Venus, depending on how you define "visit": https://en.wikipedia.org/wiki/Venera

  "Among the other results, probes of the series became the first man-made devices
   to enter the atmosphere of another planet (Venera 4 on October 18, 1967), to
   make a soft landing on another planet (Venera 7 on December 15, 1970), to
   return images from the planetary surface (Venera 9 on June 8, 1975), and to
   perform high-resolution radar mapping studies of Venus (Venera 15 on June 2,
   1983). The entire series could be considered highly successful."

Re: New Horizons: Nasa spacecraft speeds past Pluto

#192

Post by m-app » Tue, Jul 14, 2015, 5:48 PM UTC

Cthulhu_ wrote: post #180

kartikkumar wrote: post #147

Earlier quoted context omitted.

I realise that I made an unexplained logical leap to get to the last comment. Basically, based on my professional experience as a planetary scientist, it's my belief that the reason we don't have more satellites cruising through the Solar System is that we (and I mean scientists, engineers, administrators etc.) continue to fail in communicating their true value to the average person on the street. I think that media…

Right now, companies like Facebook and Google are working on bringing the internet to countries that don't have good access to it yet; if it wasn't for the lag (and cost), I'm sure they would've invested heavily into a sattelite internet network. I see a small / niche market in space tourism; Virgin Intergalactic is probably going to get on there. But it'll be limited to those that can shell out 100K for it. There wa…

100k to go Intergalactic? NASA would love such a service!

Re: New Horizons: Nasa spacecraft speeds past Pluto

#193

Post by cgriswald » Tue, Jul 14, 2015, 5:52 PM UTC

dalke wrote: post #124

blakecaldwell wrote: post #83

It kills me we're not gonna orbit Pluto.

There is a mission study which says it's feasible to orbit Pluto. http://www.esa.int/gsp/ACT/doc/PRO/ACT-RPR-PRO-ISTS2004-Plut... . It requires 4 RTGs, nuclear electric propulsion, and 18 years of travel time. You might be dead by the time that actually happens, so better to be killed by sorrow of only getting fly-by data than the agony of having only what Hubble and its successors can resolve.

It can't actually happen. NASA only has enough Pu-238 for three more RTGs.

Re: New Horizons: Nasa spacecraft speeds past Pluto

#194

Post by teraflop » Tue, Jul 14, 2015, 5:54 PM UTC

bdamm wrote: post #161

thwest wrote: post #155

Earlier quoted context omitted.

Perhaps no significantly bright stars. I find it unlikely that there are zero stars in that field of view, especially since the probe and planet are most likely roughly in the plane of the galaxy.

This is basically heresy, but what I've been told is that imaging stars from space is actually more difficult, because there is no diffusion of the local atmosphere to help increase the perceived size of the point light source.

If you're saying that the images of all of the point sources manage to "miss" the image-sensing regions of the camera sensor, then I seriously doubt that explanation.

For one thing, it assumes that only a small fraction of the image sensor's surface is actually capable of detecting light, which would make it very inefficient. Typical consumer digital cameras can capture over 30% of the incoming energy, and presumably New Horizons' camera can do better, being specifically designed for a low-light environment.

More importantly, no atmospheric "diffusion" is required to spread out the incoming light, because it's occurring anyway through diffraction at the camera's aperture. The angular resolution of the LORRI camera is specified as about 1 arcsecond, which is comparable to the atmospheric seeing conditions on a relatively clear night on Earth.

Re: New Horizons: Nasa spacecraft speeds past Pluto

#195

Post by mturmon » Tue, Jul 14, 2015, 5:54 PM UTC

david-given wrote: post #149

Retric wrote: post #137

Earlier quoted context omitted.

If you have ever been to a high school pep rally; most people don’t actually care about the school. But, it’s fun to stand up and yell really loudly. Nationalism is IMO deeper than that. To use a EU example, many people in Greece complain about countries that are giving them money. “How dare they attach strings when handing us money!!!” That’s nationalist in ways I have trouble understanding.

Speaking as a UK citizen living in Switzerland, I have to ask: what is a high school pep rally?

You are in for a treat. This excerpt from Fast Times at Ridgemont High (worth watching in its entirety) tells you what you need to know: https://www.youtube.com/watch?v=NLTTugZ4BIw

Re: New Horizons: Nasa spacecraft speeds past Pluto

#196

Post by mmagin » Tue, Jul 14, 2015, 5:57 PM UTC

grinich wrote: post #166

chasing wrote: post #160

Earlier quoted context omitted.

Any actual engineer will probably find this comment painfully naive, but here we go: If it's infeasible to slow down to get into orbit or land on Pluto, what about the feasibility of designing a probe to impact Pluto at XX km/sec and survive well enough to send back data. Like, fire a (metaphorical) bullet full of scientific instruments directly into the surface of the planet. Is it simply that we have no way to buil…

A bullet travels about 1,700 MPH. New Horizons is going about 36,300 MPH. The probe weighs 480 kilograms, so it's kinetic energy is approximately 63.2 Gigajoules. For reference, this is like 15 tonnes of TNT released on impact. Hard to make something that survives those kind of conditions.

I wonder if it would be more interesting to fire a sizable dumb projectile into Pluto and then after you've past it a bit (with proper alignment of the spacecraft, sun, and pluto) observe the absorption spectrum of the gas/dust cloud produced.

Re: New Horizons: Nasa spacecraft speeds past Pluto

#197

Post by unclebucknasty » Tue, Jul 14, 2015, 6:03 PM UTC

chasing wrote: post #160

kartikkumar wrote: post #89

Quote from a friend of mine on the team: "After 9.5 years and 6 billion km, we made it to Pluto 72 seconds ahead of schedule." Amazing! The views of Pluto and Charon already reveal how incredibly fascinating this system is. The dichotomy of their surface colours will most definitely lead to further insight into formation processes in the Kuiper Belt. Just such a shame that we can't land this time around. With the vol…

Any actual engineer will probably find this comment painfully naive, but here we go: If it's infeasible to slow down to get into orbit or land on Pluto, what about the feasibility of designing a probe to impact Pluto at XX km/sec and survive well enough to send back data. Like, fire a (metaphorical) bullet full of scientific instruments directly into the surface of the planet. Is it simply that we have no way to buil…

Wonder if there would have been any way to use Neptune to slow the probe? Probably would have been travelling too fast, I'm guessing.

Re: New Horizons: Nasa spacecraft speeds past Pluto

#198

Post by ebetica » Tue, Jul 14, 2015, 6:05 PM UTC

jsprogrammer wrote: post #186

jccooper wrote: post #168

Earlier quoted context omitted.

Bullet goes about 1.2 km/s at best. New Horizons is going ~14 km/s relative to Pluto. That's a heck of an impact to survive. You could do it on Earth by braking in the atmosphere, but there's not a lot of that on Pluto.

If you were trying to land, you would use a different trajectory that doesn't result in you traveling 14 km/s to Pluto?

That would take a while to get there.

Re: New Horizons: Nasa spacecraft speeds past Pluto

#199

Post by anigbrowl » Tue, Jul 14, 2015, 6:05 PM UTC

kartikkumar wrote: post #147

japhyr wrote: post #131

Earlier quoted context omitted.

I love HN for things like this - personal accounts of people associated with groundbreaking projects. Thanks for sharing. Most of your post is about visiting planets and exploring the solar system, but you close witha comment about disrupting science communication. What aspects of science communication are you referring to?

I realise that I made an unexplained logical leap to get to the last comment. Basically, based on my professional experience as a planetary scientist, it's my belief that the reason we don't have more satellites cruising through the Solar System is that we (and I mean scientists, engineers, administrators etc.) continue to fail in communicating their true value to the average person on the street. I think that media…

Great points and great blog too. Paradoxically I think what's missing is more manned space exploration - people have a genuine interest in seeing other planets and knowing about space in general, but this interest is tempered by the painful awareness that that we will never get to visit them, so that it's like being on an island with a tall tower and a great telescope (through which we can see enticing other places) but no way of building a boat.

Of course going into space is so expensive and so few of us would make the cut as astronauts that hardly anyone realistically expects to become a space explorer, but we would like to live vicariously through other space explorers, but this isn't possible if our explorers never go anywhere. I think the reason people get so wrapped up in the story of the Mars rovers and the Rosetta/Philae mission was that those probes are the most relateable things since people walked on the Moon in the 1970s.

Really, I think we should be doing manned Moon missions regularly. People point out that there's nothing on the Moon that we want, which is sort of true (although we've learned so much since the last time we went that we should reconsider that angle) but that's a dreadfully consumerist mindset. The Moon is a (relatively) accessible destination that we could use as a proving ground for interplanetary exploration techniques. But more importantly, making regular visits or having a permanent outpost there gives people something to project their imaginations onto (including their political and technological imagination). I have a small collection of old newspapers and my favorite is one published the day after the first Moon landing with the simple headline 'Men on Moon'. Reading it still gives me a shiver of excitement, followed by disappointment that we abandoned Moon exploration by the mid 1970s.

One often-forgotten detail of the Moon landing was that at the time there was a Russian observer spacecraft orbiting the Moon, and it dropped down to within 10 miles of the surface at the time of the landing (presumably to observe what the Americans were up to). I saw Neil DeGrasse Tyson on Charlie Rose last week and he was joking that his favorite daydream is meeting the Chinese President at a conference and persuading him to leak a fake memo saying China aims to land a man on Mars, which would galvanize the American body politic back into serious investment in space. Sad but true.

Re: New Horizons: Nasa spacecraft speeds past Pluto

#200

Post by cgriswald » Tue, Jul 14, 2015, 6:12 PM UTC

huuu wrote: post #2

It seems Pluto has much less craters than our moon. Is this because our moon is much closer to a heavy body which attracts all kinds of objects? Anyway: wow! The quality of this preview is already amazing. Waiting for the high res version :)

I think the main reason is that Pluto has an active atmosphere; it snows. Plutos icy surface may be somewhat active as well, so craters may disappear over time in a way that the craters on the moon cannot.

However, there may be other factors:

1. As you note, the mass of the Earth-Moon system is much greater than the mass of the Pluto-Charon system.

2. In the Earth-Moon system, the moon is the outer protector. In the Pluto system, there are five smaller protectors and Pluto is the protected.

3. The inner solar system is a small, dense region closer to the gravity of the sun and gas giants. Objects thrown in our direction are likely to stick around. In contrast, the Kuiper Belt isn't very dense and objects thrown in that direction not only have more places to go, but may be on their way out of the solar system or into extended hyperbolic orbits.

3. KBOs aren't very dense, so even impacts which occur may not create massive craters.