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

New Horizons: Nasa spacecraft speeds past Pluto

bbc.co.uk

Post reply on HN
Print view View original

211–220 of 309 posts

Re: New Horizons: Nasa spacecraft speeds past Pluto

#211

Post by ars »

zkhalique wrote: post #205

Why didn't it stop to look around? Smell the proverbial roses? Wasn't that its main mission? Or is it now going to check out other Kuiper belt objects?

It's moving too fast for it to stop. It's not [currently] possible to ship enough fuel for it to stop by using rockets. And there is no good atmosphere for it to use to stop (plus we don't have enough information about the atmosphere to design anything yet).

So it will just do a very short flyby, then spend the next year or two sending the data back to Earth. After that it's not decided, but probably some Kuiper belt object like you suggest.

Re: New Horizons: Nasa spacecraft speeds past Pluto

#212

Post by ars »

cgriswald wrote: post #193
dalke wrote: post #124

Earlier quoted context omitted.

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.

They can use Americium-241, it's not quite as good, but it has some advantages, plus it's in much larger supply.

Re: New Horizons: Nasa spacecraft speeds past Pluto

#213

Post by liquidise »

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…

So, for such an impact, you would almost certainly need the strongest bouncing lander ever produced. However, Pluto's escape velocity only is about 1/10th the speed of NH.

This means that if that first bounce upon impact would result in even 10% of the initial velocity, it will literally bounce out of the system and back towards the sun.

Re: New Horizons: Nasa spacecraft speeds past Pluto

#214

Post by ars »

mFixman wrote: post #207
Mahn wrote: post #106

Apparently it snows on Pluto: Pluto has an atmosphere. It snows on Pluto and the snow sublimates back into the atmosphere. https://twitter.com/OSIRISREx/status/620932748824285184

I find it absolutely amazing that nobody knew this 12 hours ago.

Sorry to burst your bubble but this was known years ago. The information is not from this mission.

Google for "pluto atmosphere collapse" and set the date range to before Aug 2013.

Re: New Horizons: Nasa spacecraft speeds past Pluto

#215

Post by MichaelGG »

ceejayoz wrote: post #172
grinich wrote: post #166

Earlier quoted context omitted.

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.

Plus, probes that far out have worse-than-dialup transmission rates. It takes 42 minutes to return a single photo from the LORRI camera. Bursting large amounts of data out in a short period of time before impact isn't feasible. http://www.planetary.org/blogs/emily-lakdawalla/2015/0130080...

You would put something else in orbit and have high bandwidth communication to it and relay from there.

Re: New Horizons: Nasa spacecraft speeds past Pluto

#217

Post by ars »

rootbear wrote: post #103
e0m wrote: post #97

Traveling at 16km/s for 9.5 years would dilate time by almost 300 minutes! Not only is there a 4.5 hr delay because of the speed of light, there's an extra 300 min of relativity correction.

Whoa! I hadn't thought about that. The speed of New Horizons hasn't been constant, of course, but the accumulated time difference is probably close to what you calculated. There would also be a correction due to it being farther out of the Sun's gravity well, but that's a much trickery calculation.

(Just a note: His math is off.)

You also have to account for the dilation caused by the force of launch itself.

But then you have to subtract the dilation of Earth.

> There would also be a correction due to it being farther out of the Sun's gravity well

Because it is in free-fall relative to the Sun there is no Solar gravitational dilation.

Re: New Horizons: Nasa spacecraft speeds past Pluto

#218

Post by drjesusphd »

raverbashing wrote: post #201
Cthulhu_ wrote: post #175

Earlier quoted context omitted.

It's theoretically possible, it'd just require a lot of fuel to slow the craft down enough to survive a landing. source: I've played Kerbal Space Program. If you speak maths (I don't), you could probably do them; the calculations are relatively simple: https://en.wikipedia.org/wiki/Delta-v .

No, it is much much harder. Especially the survival part Delta-v is literally Physics 101 Landing on Mars is hard, but feasible. Because it has a thick atmosphere to help with the braking Sure, it adds a lot of complications as well, but it is a very good way of slowing your craft enough for other braking systems to work (like rockets, parachutes, etc) Of course, bodies with little atmosphere also have a small gravit…

> No, it is much much harder. Especially the survival part

Please elaborate. What is dangerous about a braking burn? Sure, it's harder (because you need to carry that fuel), but not impossible in principle.

> Sure, it adds a lot of complications as well, but it is a very good way of slowing your craft enough for other braking systems to work (like rockets, parachutes, etc)

I'm sorry, when do rockets not work?

Re: New Horizons: Nasa spacecraft speeds past Pluto

#219

Post by Freaky »

prewett wrote: post #206
lmorris84 wrote: post #59

Does anyone know how they colour correct these images? I'm guessing there isn't a robotic arm holding up a test card in front of the camera :-)

I think they usually have a black and white camera with filters of specific wavelengths, some of which roughly correspond to red, green, blue, and they combine them. The color pictures I've seen from Mars and Cassini usually say "approximate true color."

They have no green (495-570nm) filter, just panchromatic (400-975nm), blue (400-550nm), red (540-700nm), near-IR (780-975nm) and narrow-band methane (860-910nm).

Re: New Horizons: Nasa spacecraft speeds past Pluto

#220

Post by drjesusphd »

Cthulhu_ wrote: post #178
artur_makly wrote: post #173

So this got me thinking... is there a way to forecast our space-travel capacity into the far future? Could we conceivably create a formula that takes into account all of humanity's previous milestones of technological breakthrough's and the distances they have achieved for us.. and project where we could be 100, 500, 1000 yrs from now? Perhaps there is a vague velocity pattern we can derive from a plethora of histori…

A formula? No, probably not; the thing with space exploration is that it depends on the one hand on money, i.e. government funding or commercial exploitation, and on the other on physics - getting something into space, let alone propel it far away, is a very costly process when it comes to fuel and whatnot required - which increases exponentially the more you want to achieve out there. Although companies like Virgin…

> Still though, practically speaking, getting anything into orbit is hard enough.

As the saying goes, "low Earth orbit is halfway to anywhere in the solar system".

Post reply on HN