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Star 48b Third-stage Motor, Leaving the solar system
Guido
post Jan 21 2006, 11:49 AM
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I suppose the STAR 48B third-stage, which put New Horizons on its trajectory towards Jupiter, follows about the same flight-path as the New Horizons spacecraft itself. If this is the case, will it too in the end leave our solar system?
Or has it been deflected after seperation from the spacecraft?
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Alan Stern
post Jan 21 2006, 12:11 PM
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QUOTE (Guido @ Jan 21 2006, 11:49 AM)
I suppose the STAR 48B third-stage, which put New Horizons on its trajectory towards Jupiter, follows about the same flight-path as the New Horizons spacecraft itself. If this is the case, will it too in the end leave our solar system?
Or has it been deflected after seperation from the spacecraft?
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It's going interstellar. But wll miss Pluto considerably, by >>10^7 km.

-Alan
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tasp
post Jan 21 2006, 02:38 PM
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Too late now, and probably unworkable across the necessary distances, but a laser retroreflector on an inert booster stage might have been a pretty good experiment for the 'Pioneer Effect'.
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ljk4-1
post Jan 21 2006, 04:38 PM
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QUOTE (tasp @ Jan 21 2006, 09:38 AM)
Too late now, and probably unworkable across the necessary distances, but a laser retroreflector on   an inert booster stage might have been a pretty good experiment for the 'Pioneer Effect'.
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Has anyone ever made scientific use of these final boost stages before they are sent aloft into the Great Unknown? Seems like a wasted opportunity otherwise.


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Bob Shaw
post Jan 21 2006, 05:25 PM
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QUOTE (tasp @ Jan 21 2006, 03:38 PM)
Too late now, and probably unworkable across the necessary distances, but a laser retroreflector on  an inert booster stage might have been a pretty good experiment for the 'Pioneer Effect'.
*



That's an interesting idea, especially on a spinning solid stage (not a lot of venting going on as it's a solid, use residual attitude control gas (if any) to spin the thing up, no IR from the RTGs). It's the sort of situation where aperture synthesis observations would be the way to go, perhaps amateur-based. I wonder whether laser light from different locations can be tuned to act as one big lump of light (you know what I mean!)? If the LRRR cubes could be 'tuned' somehow then perhaps by putting half a dozen on the motor then you could even gain some notion of the attitude of the stage over the years, too.

Bob Shaw


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djellison
post Jan 21 2006, 06:33 PM
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Obviously retro reflectors work out to 400k km, but how far out would they work beyond that? Perhaps one could do radar reflection using Arecbo / DSN instead?

Also - there's no real way of knowing, (perhaps less so with the solid 48b than a liquid upper stage) what potential small forces are being generated by outgassing of remaining fuel, its exact mass etc.

Doug
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Bob Shaw
post Jan 22 2006, 02:37 AM
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QUOTE (djellison @ Jan 21 2006, 07:33 PM)
Obviously retro reflectors work out to 400k km, but how far out would they work beyond that?  Perhaps one could do radar reflection using Arecbo / DSN instead?

Also - there's no real way of knowing, (perhaps less so with the solid 48b than a liquid upper stage) what potential small forces are being generated by outgassing of remaining fuel, its exact mass etc.

Doug
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Doug:

I think that the laser option is best, inasmuch as you've got 30 years of laser technology upgrades to apply to such an experiment; as for the outgassing, I doubt there's much. Anyway, it's a *cheap* experiment!

Bob Shaw


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RNeuhaus
post Jan 22 2006, 03:10 AM
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QUOTE (Alan Stern @ Jan 21 2006, 07:11 AM)
It's going interstellar. But wll miss Pluto considerably, by >>10^7 km.

-Alan
*

In the other words, the Star 48B will follow up the NH's track until Jupiter? After Jupiter, will continue following farther or closer to NH toward Pluto? I assume that NH will make many TCM, so every time NH performs the TCM, the Star 48 B will be lagging even farther.

Have the NH team been tought about the usefulness of mass of Star 48 B to hit on Pluto as an experiment about the Pluto's properties of structure and at the same time Clyde will be able to land on that..... smile.gif

Rodolfo
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mchan
post Jan 22 2006, 07:17 AM
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QUOTE (RNeuhaus @ Jan 21 2006, 07:10 PM)
Have the NH team been tought about the usefulness of  mass of Star 48 B to hit on Pluto as an experiment about the Pluto's properties of structure and at the same time Clyde will be able to land on that.....  smile.gif
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That would be truly a hole in one type of shot to hit Pluto without any tracking and course corrections after motor burnout!!
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Alan Stern
post Jan 22 2006, 11:17 AM
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We are setting up for our first course correction. Without it we would miss Pluto
by millions of miles. The third stage has no ability to make a course correction
and will therefore miss by this amount.

-Alan
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edstrick
post Jan 22 2006, 12:58 PM
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Alan: Any serendipitious distant asteroid flyby's on the to-Jupiter trajectory... with maximum image size over 1 1/2 pixels?
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tasp
post Jan 22 2006, 02:55 PM
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QUOTE (edstrick @ Jan 22 2006, 06:58 AM)
Alan:  Any serendipitious distant asteroid flyby's on the to-Jupiter trajectory... with maximum image size over 1 1/2 pixels?
*



Or an 'outie' satellite of Jupiter? Seems like there are 60 or so now that we know of. Is the density of objects in the outer moon belt of Jupiter higher than the Kuiper Belt?

It would be useful to have an image to compare to any pictures we might get someday of any of Jupiters Trojan population. And to compare to the outer asteroid belt population.

Similarites of distant small Jovian satellites to D-type asteroids may also have some relevance in studying Cassini Regio and perhaps the dark crater floors of Hyperion.
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tasp
post Jan 22 2006, 03:03 PM
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Both Voyagers had Centaur stages that left earth at interesting velocities in interesting directions, too. And the Voyager final solid stages would have had trajectories even closer to the the Voyagers.

Wonder what happened to them?
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Alan Stern
post Jan 22 2006, 04:10 PM
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All.

Things are going well here at the APL MOC. New Horizons is operating
virtually flawlessly. TCM 1a and 1b are planned for 28 Jan and 30 Jan,
respectively, with a total delta-V of 18 m/s-- which is far smaller than
the 92 m/s budgeted for pre-flight. Good news!

Today we are planning to complete the spacecraft's planned spin down to 5
RPM (was 68 RPM for the STAR-48 firing, is now 19.2 RPM after an open-loop
burn on launch day). Once we slow it down this afternoon, we'll do the
initial star tracker turn ons. Until then, we're still relying on the sun
sensors and IMUs-- both of which are performing very well. The s/c temps
are running a little hot, but that's just due to our attitude combined
with our <1 AU helio distance (we're inside 1 AU because we launched near
Earth's perihelion).

About the heliocentric distance, we will be inside 1 AU until late on 29
Jan UT. That makes us officially an inner planet mission for the first 10
days, I guess.

We will pass the orbit of Mars on 8 April, just a little after MRO
gets there, and it had a 5.5 month head start.

FYI-- The C/A to Jupiter is going to be at approx 6 hrs UTC on 28 Feb
2007. A better number will be forthcoming, but that is good to an accuracy
of better than an hour already. C/A is to be at 32 RJ.

Because we have to slow down in TCM-1a and TCM-1B by those 18 m/s,
our intrepid Boeing STAR-48 third stage will beat New Horizons to
Jupiter by 6 hrs. However, because it will not hit the Pluto aim point, it will not
beat us to Pluto (a relief-- can you imagine us having to be the second to
Pluto after all this, having been beat by a derelict Boeing upper stage?).
In fact, the projected C/A distance of the third stage to Pluto will be
213 million km (well over 1 AU), occurring on 15 Oct 2015.

-Alan
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Redstone
post Jan 22 2006, 04:19 PM
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"C/A is at 32 RJ"

For comparison, the outermost Galilean moon, Callisto, is at about 26 RJ.

Alan, thanks for all the details. Do you have any idea yet what targets look promising for the Jupiter encounter?
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