by neufer » Tue Oct 06, 2015 4:29 pm
Chris Peterson wrote:Rusty Brown in Cda wrote:
I get the impression from both the video and the text that New Horizons didn't really "fly past" Pluto but rather looped around it, using Pluto's gravity, or even went into orbit. Most news reports seem to indicate that the spacecraft just flew by and got a quick glance in passing, then headed on further into space.
New Horizons essentially passed through the Pluto system in a straight line. The gravity of the pair was insufficient to significantly deflect the spacecraft. It did not loop at all, it did not enter a closed orbit.
Pluto has an escape velocity (
Ve) of 1.212 km/s at a radius of 1,186 km.
The
local escape velocity
at New Horizons at closest approach (i.e., 12,500 km
from the surface)
- was (Venh) ~ 0.357 km/s ~ 1.212 / sqrt(1 + [12,500/1,186]).
At that time New Horizons was traveling at (
Vnh) = 13.78 km/s
- or ~38.6 times the local escape velocity (Venh)
The deflection angle = sin
-1(
Venh/Vnh)
2 ~ sin
-1(1/38.6
2) radians ~ 2 arc minutes.
[quote="Chris Peterson"][quote="Rusty Brown in Cda"]
I get the impression from both the video and the text that New Horizons didn't really "fly past" Pluto but rather looped around it, using Pluto's gravity, or even went into orbit. Most news reports seem to indicate that the spacecraft just flew by and got a quick glance in passing, then headed on further into space.[/quote]
New Horizons essentially passed through the Pluto system in a straight line. The gravity of the pair was insufficient to significantly deflect the spacecraft. It did not loop at all, it did not enter a closed orbit.[/quote]
Pluto has an escape velocity ([b][color=#FF0000]V[sub]e[/sub][/color][/b]) of 1.212 km/s at a radius of 1,186 km.
The [u]local[/u] escape velocity [u]at New Horizons[/u] at closest approach (i.e., 12,500 km [u]from the surface[/u])
[list]was ([b][color=#FF0000]V[sub]enh[/sub][/color][/b]) ~ 0.357 km/s ~ 1.212 / sqrt(1 + [12,500/1,186]).[/list]
At that time New Horizons was traveling at ([b][color=#0000FF]V[sub]nh[/sub][/color][/b]) = 13.78 km/s
[list] or ~[b][u]38.6 times the local escape velocity[/u][/b] ([b][color=#FF0000]V[sub]enh[/sub][/color][/b]) :!: [/list]
The deflection angle = sin[sup]-1[/sup]([b][color=#FF0000]V[sub]enh[/sub][/color]/[color=#0000FF]V[sub]nh[/sub][/color][/b])[sup]2[/sup] ~ sin[sup]-1[/sup](1/38.6[sup]2[/sup]) radians ~ 2 arc minutes.