ISS orbital decay if unnattened?

[ace5]

Just for curiosity, for how long can the ISS stay in orbit unmanned if left without any orbital and attitude correction manouvrering?

 

[mrmorris]

<font color="yellow">"...how long can the ISS stay in orbit..."</font><br /><br />There are too many factors involved to state a figure with any precision. Just as an example, Skylab was expected to stay in orbit until ~1983 after the final Apollo-Skylab mission bosted their orbit as they were leaving in 1974. Instead, solar activity caused the Earth's atmosphere to bulge, increasing drag on the station. It re-entered in 1979, four years before predicted (a bit over half of the <i>projected</i> lifetime).

 

[drwayne]

Indirectly addressing your question, consider this:<br /><br />http://yarchive.net/space/orbits/orbital_lifetimes.html<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[ace5]

anyone knows if there is a software for orbital predictions?

 

[drwayne]

Yes, I have found some interesting programs at various times by googling about.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[ace5]

It would be useful a software in wich you put the spacecraft data and a given date, so it can calculate the reentry date if there is no maneuver.<br />I found this link<br />http://www.ips.gov.au/Satellite/3/2<br />to an applet, but it runs only online.

 

[chmee]

Skylab was predicted to be until 1983? Wow. Did NASA plan to have the Shuttle visit it if it stayed up? Or was the fact that it had been abondoned for so long that it would have been useless when the first shuttle launched in 1981?

 

[ace5]

I think that Skylab was left in an 450 km orbit, with a few corrections by the RCS ( I aways wondered where the RCS thrusters in Skylab were located) being made shortly after the departure of the last manned mission.<br />I was intended that the station would stay up there for 11 years.<br />I dont know if there were any further RCS firings for more attitude and orbital corrections.

 

[drwayne]

There were some discussions in this area on another thread n the last week or so. There were plans to have the shuttle transport some reboost equipment to it.<br /><br />It should be remembered that Skylab was an experiment, a space station done, relatively speaking, on the cheap. It is debatable how useful it would have been to keep it going.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[mrmorris]

<font color="yellow">"Did NASA plan to have the Shuttle visit it if it stayed up?"</font><br /><br />Yes -- part of the plan was to have the shuttle visit and provide a reboost. However, the shuttle was several years late flying and Skylab was several years early falling. It was mothballed as best they could after leaving. It still contained water and some provisions, although there were questions about how good they'd be. There were other issues as well.<br /><br />Astronautix has an article that talks about this some more. Pulling the most relevant bit:<br /><br /><i>"The station, never designed to be resupplied, was retired after the third mission ended on February 8, 1974. On the remote chance somebody else would venture aboard, the departing astronauts left a bag of food, clothing, film, and camera filters near the front hatch, tied securely to the telescope control panel. As they left the station, they removed the inside locking pin from the airlock hatch -- in effect, putting out the welcome mat. <br /><br />In the end, it was the sun that spelled doom for Skylab. The final crew used their Apollo spacecraft to nudge Skylab high enough to keep the station in orbit until sometime in 1983. But in the late 1970s solar activity intensified, heating and expanding the upper atmosphere enough to increase the drag on the space station. As Skylab's orbit decayed and its life expectancy decreased, the shuttle program encountered more and more delays. Early plans had called for the reboost mission to be undertaken on the sixth shuttle launch, but schedule pressures pushed it as far ahead as the second mission. However, STS-2 wasn't launched until November 12, 1981, more than two years after Skylab's charred remains had dropped across western Australia when the spacecraft fell on July 11, 1979. "</i>