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View Full Version : New Horizon's Velocity Question.

BigDon
2015-Jul-15, 06:55 PM
Barring course changes or an unscheduled sudden stop, does New Horizons have enough velocity for a full solar escape or is it going to become a long period comet? (Cometoid?)

Swift
2015-Jul-15, 07:08 PM
According to this table (http://www.heavens-above.com/SolarEscape.aspx?lat=0&lng=0&loc=Unspecified&alt=0&tz=UCT) from the Heaven's Above website, the speed, relative to the sun, of Pioneer 10 and 11 are 12.0 and 11.3 km/sec, Voyager 1 and 2 are 15.4 and 17.0 km/sec, and New Horizons is 14.5 km/sec. Since the Pioneers are on the way out, I assume NH will be too. According to wikipedia (https://en.wikipedia.org/wiki/Escape_velocity#List_of_escape_velocities), at Neptune, the solar escape velocity is about 8 km/sec.

grapes
2015-Jul-15, 09:14 PM
The nice thing about escape velocity is that it doesn't matter which direction you're heading, you'll escape (barring atmospheric or lithospheric friction)

Van Rijn
2015-Jul-16, 01:46 AM
Yep, it's heading out. I checked that a long time ago when I added my name to the list that went on the CD. I get a kick out of the idea that a little something of me (and a few hundred thousand other people) is going interstellar.

a1call
2015-Jul-16, 03:37 AM
What's the next target?
If none, why not stay and orbit?

Jens
2015-Jul-16, 03:56 AM
What's the next target?
If none, why not stay and orbit?

Because the people who designed the thing forgot to put brakes on it.

Hornblower
2015-Jul-16, 03:56 AM
What's the next target?
If none, why not stay and orbit?
That's a very good question. Carrying the fuel necessary for such a maneuver, along with all of the instruments, would have required a larger launch vehicle which could have been a budget buster. As I understand it, it was a hard sell to get this mission funded even without the orbital capability.

Shaula
2015-Jul-16, 04:19 AM
Yep, it's heading out. I checked that a long time ago when I added my name to the list that went on the CD. I get a kick out of the idea that a little something of me (and a few hundred thousand other people) is going interstellar.
*crunch*
"What just hit my brand new space ship? This is a Zarvg custom job! Have they any IDEA how much this cost?"
"It is some kind of metal boxy thing. No idea what it does. But it looks like it was moving pretty fast, it had to be deliberative."
"OK, track it back to where it came from."
"No need - looks like the owners signed it!"
"Heh, OK Mr V..a...n... R..i..j..n, prepare for an insurance claim that will be spoken of in hushed whispers millennia from now."

Noclevername
2015-Jul-16, 04:35 AM
And it might do significant damage if it hits your car, according to What If XKCD (https://what-if.xkcd.com/137/).

How fast is 14 kilometers per second? Here's my favorite comparison for putting that speed in perspective: If you were standing at one end of a football field and fired a gun toward the other end, right while New Horizons flew past you, the spacecraft would reach the far end zone before the bullet made it to the 10-yard line.[

a1call
2015-Jul-16, 05:52 AM
Couldn't they have at least flown by a couple of feet closer?
9.5 years would have taken very little fuel to adjust to a closer angle of flyby. Wouldn't it?

VQkr
2015-Jul-16, 06:29 AM
Couldn't they have at least flown by a couple of feet closer?
9.5 years would have taken very little fuel to adjust to a closer angle of flyby. Wouldn't it?

The spacecraft has maneuvering thrusters to change its orientation and make course adjustments. It flew just about exactly where the mission team planned for it to go.

VQkr
2015-Jul-16, 06:35 AM
What's the next target?
If none, why not stay and orbit?

It took a 570,000 kg rocket to get the 478 kg probe up to 16.5 km per second at launch. To get slowed down again at Pluto, a similarly-sized amount of fuel would be needed. But to launch that fuel so it would be available at the end of the trip to Pluto, a much, much, much bigger rocket would have been needed at the start. The heaviest rocket ever launched was almost 3,000,000 kg; that still wouldn't have been close to enough.

Jens
2015-Jul-16, 07:12 AM
The spacecraft has maneuvering thrusters to change its orientation and make course adjustments. It flew just about exactly where the mission team planned for it to go.

I don't know the details, but I imagine also that the closer you get, (a) the bigger the risk of an accidental collision with something becomes and (b) the more data storage you need because you are taking more photos, and (c) the faster the camera has to be in order not to miss anything. So clearly, you wouldn't want to zip along 100 meters off the surface. There is a balance, and I suppose the team made a choice based on the risk-benefit analysis.

Jens
2015-Jul-16, 07:15 AM
It took a 570,000 kg rocket to get the 478 kg probe up to 16.5 km per second at launch. To get slowed down again at Pluto, a similarly-sized amount of fuel would be needed. But to launch that fuel so it would be available at the end of the trip to Pluto, a much, much, much bigger rocket would have been needed at the start. The heaviest rocket ever launched was almost 3,000,000 kg; that still wouldn't have been close to enough.

It could have used "lithobraking" of course. As long as you don't care about getting the data back. And gotten some VERY close-up images that we would never be able to see.

Noclevername
2015-Jul-16, 08:38 AM
Couldn't they have at least flown by a couple of feet closer?
9.5 years would have taken very little fuel to adjust to a closer angle of flyby. Wouldn't it?

Why?

We already have detailed pictures of its surface, what benefit would there be in being physically closer?

NEOWatcher
2015-Jul-16, 12:37 PM
To get slowed down again at Pluto, a similarly-sized amount of fuel would be needed.
Not when you consider gravity wells.
It takes a delta V (https://dannypagano.files.wordpress.com/2013/12/wgoy3qt.png) of 18.17 km/s to get to Pluto. It would take another 3.41 km/s to slow it to an orbit of Pluto.
Certainly a much bigger rocket would be necessary, but not similarly-sized,

Swift
2015-Jul-16, 01:16 PM
Originally Posted by VQkr
The spacecraft has maneuvering thrusters to change its orientation and make course adjustments. It flew just about exactly where the mission team planned for it to go.I don't know the details, but I imagine also that the closer you get, (a) the bigger the risk of an accidental collision with something becomes and (b) the more data storage you need because you are taking more photos, and (c) the faster the camera has to be in order not to miss anything. So clearly, you wouldn't want to zip along 100 meters off the surface. There is a balance, and I suppose the team made a choice based on the risk-benefit analysis.
Also, the closer to the surface you go, the smaller percentage of the total area of Pluto you will see.

George
2015-Jul-16, 01:35 PM
Have they stated what is the next step...hibernation? With larger scopes being built, perhaps they, or NH itself, will discover objects ahead that will only take a small course correction to get some pretty pics.

Dave12308
2015-Jul-16, 01:49 PM
Yep, it's heading out. I checked that a long time ago when I added my name to the list that went on the CD. I get a kick out of the idea that a little something of me (and a few hundred thousand other people) is going interstellar.

Yes, I am a bit disappointed in the fact that space is a rather recent interest of mine, so back when this was going on I didn't even know about it. Or any planned space missions. I used to strictly be interested in earth based aviation.

VQkr
2015-Jul-16, 07:18 PM
Not when you consider gravity wells.
It takes a delta V (https://dannypagano.files.wordpress.com/2013/12/wgoy3qt.png) of 18.17 km/s to get to Pluto. It would take another 3.41 km/s to slow it to an orbit of Pluto.
Certainly a much bigger rocket would be necessary, but not similarly-sized,

That assumes minimum energy (Hohmann) transfers, which take a looong time to reach the outer solar system. The mission planners presumably didn't want to wait 50 years for the spacecraft to reach Pluto so they could orbit it with a (still substantial) 3.4 km/s dV (not least because it would need a different power system to stay functional that long). The launch put the probe on a sun escape trajectory, and the Jupiter flyby gave it even more velocity. It would have taken >10 km/s of dV to enter Pluto orbit with the transfers used.

NEOWatcher
2015-Jul-17, 01:31 AM
That assumes minimum energy (Hohmann) transfers, which take a looong time to reach the outer solar system. The mission planners presumably didn't want to wait 50 years for the spacecraft to reach Pluto so they could orbit it with a (still substantial) 3.4 km/s dV (not least because it would need a different power system to stay functional that long). The launch put the probe on a sun escape trajectory, and the Jupiter flyby gave it even more velocity. It would have taken >10 km/s of dV to enter Pluto orbit with the transfers used.
Yes, all that is true. I oversimplified it to get my point across which was that the deceleration is much less than the initial launch.
That 10km/s is not much more than it took to get it out of Earth's gravity well.
The Jupiter flyby increased the speed by 20% (heard it on this weeks NOVA episode).

WayneFrancis
2015-Jul-17, 06:38 AM
It could have used "lithobraking" of course. As long as you don't care about getting the data back. And gotten some VERY close-up images that we would never be able to see.

You mean like....crashing?

Jens
2015-Jul-17, 07:18 AM
You mean like....crashing?

Yeah, that would be another way to put it.

ngc3314
2015-Jul-17, 02:50 PM
Have they stated what is the next step...hibernation? With larger scopes being built, perhaps they, or NH itself, will discover objects ahead that will only take a small course correction to get some pretty pics.

The mission proposal always included the desirability of a flyby of something farther out in the Trans-Neptune belts. Using about 2 weeks of time on Hubble[1], they found (IIRC) three objects that are in principle within reach for the remaining thruster fuel. The sooner a course adjustment is made, the more leverage they have, so a decision may be coming up soon. Still, the formal funding for an extended mission has not been approved by NASA headquarters, which is why one of the questions from the "Pluto children" at a press conference brought such laughter. This would have to be a very strong contender for such extended mission funding, though.

There was a big program to look for potential flyby targets with the 8m Subaru telescope and CCD mosaic, which was not successful because early predictions of the density of small targets used an extrapolation from larger TNOs that proved to be too optimistic, and because Pluto is now in front of the galactic bulge in our view, so the imaging artifacts from high numbers of background stars wipe out a lot of real estate from deep searches.

[1] I mention this only because of the way one mission official rags on the astronomical community a lot.

StupendousMan
2015-Jul-17, 03:49 PM
[1] I mention this only because of the way one mission official rags on the astronomical community a lot.

Would that be the "planetary scientist" (not "astronomer", as he has emphasized this week) whose name rhymes with Stallen Earn?

George
2015-Jul-26, 10:49 PM
...and because Pluto is now in front of the galactic bulge in our view, so the imaging artifacts from high numbers of background stars wipe out a lot of real estate from deep searches. That is interesting and unfortunate. Thanks for the mission possibilities. I do hope they extend the mission. I have a NASA compromise suggestion: have the mission official, boulder than many, promise an impact mission. ;)

ngc3314
2015-Jul-30, 05:58 PM
While it does eliminate the possibility of asking for further mission extensions, cryobraking on a TNO severely restricts the data return..

George
2015-Jul-30, 09:25 PM
:shhh: Aren't those things hard to hit?