Question Centaur D-1T and Voyager's Long(?) Coast

[Usonian]

I am having a devil of a time finding detailed information on the Voyager 1 and 2 launches.

Voyager 1 was lunched September 5, 1977. This web page from the National Space Science Data Center gives some good details on Voyager's interplentary trajectory.
http://nssdc.gsfc.nasa.gov/nmc/spacecraftOrbit.do?id=1977-084A
This NSSDC page starts the inital leg of the interplentary cruise ("Central Body: Sun") on September 8, about 68 hours after launch.

The NASA/JPL web page for Voyager gives the same date, calling it "Earth Injection to Jupiter"
http://voyager.jpl.nasa.gov/science/hyperbolic.html

There is a similar 3 day lag (closer to 69 hours) between launch and interplanetary flight for Voyager 2.

My initial though was that the Voyagers spent 3 days in a parking orbit, but I had my doubts. I got looking into the Centaur D-1T booster. It was fueled with liquid oxygen and hydorgen, and these cryogenic fuels tend to boil off pretty quickly. I found reports of early test flights for the D-1T, from the mid-70s, and NASA was thrilled to get 7 1/2 hours coast time between engine firings.

So what is that 3-day lag between launch and "interplanetary flight" (or "Earth injection to Jupiter" depending on the source terminalogy)? Could the Voyagers have taken that much time to leave Earth's shpere of influence? That seems like an awfully slow flight. Or, by 1977, could the Centaur's coast time have been extended, with the injection burn taking place 3 days after launch? That seems like an awfully long parking orbit coast. (Although Clementine in 1998 coasted for a week in Earth orbit before beginning its boost to the Moon, so a long parking orbit coast is not unheard of.)

I do have solid information that the Viking missions, launched with the same model Titan/Centaur rocket in 1975, had maximum coast times of 28 minutes. So I am leaning toward the short coast and long time to leave Earth's SOI.

It is frustrating to have such sketchy information on the launch trajectories details for such a significant mission -- hardest Orbiter historical detective work I have ever done.

Any thoughts?

 

[garyw]

There was an episode of "The planets" that talked about it. I remember that the main person behind it all was Gary Flandro so you could Google him and see if it shows anything?

 

[BrianJ]

Hi,
first instance of trajectory data from Horizons website is for
1977-Sep-05 13:59:59.9997 (UTC)

here it is in Orbiter format vectors (courtesy of Tony's cfgData.exe)

Date MJD  43391.5833333302
 
STATUS Orbiting Earth
RPOS  7638283.10257837 -322201.954226442 -946667.080734592
RVEL  7820.1830068985  814.894769181064  12120.3639647778

However, this data set comes with a note:
1977-Sep-5 to 1986-Jan-1:
A patched conic mission-design type trajectory in which the conics
were constructed to approximately match specific events (such
satellite encounters), providing a rough accuracy.

It might be of some use, though.

Also, quite a bit of useful info in this UMSF forum thread
http://www.unmannedspaceflight.com/index.php?showtopic=4834&st=0

Best of luck with the project,
Brian

 

[Usonian]

Thank you Brits! But alas... all bollix. (However that's spelled, and whatever it means, exactly.)

I ran into the Unmanned Spacecraft forum early in my searches and got some good leads on graphics, photos and various odds and ends, but not much about launch day.

One of the postings gave some usefull mass breakdowns extracted from Voyager's Grand Tour: To the Outer Planets and Beyond, H.C. Dethloff and R.A. Schorn, 2003. Sounded great, so I ordered it from Amazon. What a frustrating little book. The authors are both professors from Texas A&M, one in history and the other in physics and astronomy. The bibliography and footnotes are impressive, but these guys are just boring story-tellers. The writing style is very dry and, well... professorial. Their story is more a list of events, rather than a flowing narrative. Worse, though, is the repetition -- successive chapters often re-tell the same events, with little variations in the details. It looks for all the world like these two professors wrote alternating chapters, couldn't agree on whose telling of particular events should stand, and so published both (dull) tellings side by side.

Although I am learning some interesting history, the technical details I want are lacking -- the book is just too thin.

I will soldier on, though -- stiff upper lip and all that.

 

[tblaxland]

Thank you Brits! But alas... all bollix. (However that's spelled, and whatever it means, exactly.)

http://en.wikipedia.org/wiki/Bollocks

"Bollocks" is a word of Anglo-Saxon origin, meaning "testicles". The word is often used figuratively in British English, as a noun to mean "nonsense"

What are they teaching kids in school these days? :dry:

 

[Usonian]

What are they teaching kids in school these days? :dry:

Kids say the darndest things. And I learn the darndest things on this forum!