ISS orbit correction canceled after engine malfunction

[radarredux]

A cargo ship docked at the International Space Station (ISS) fired its engine Wednesday to raise the space research platform into a higher orbit but in about three minutes the engine failed and the operation was canceled.<br /><br />http://www.itar-tass.com/eng/level2.html?NewsID=2533144&PageNum=0

 

[tmccort]

How long does the station have before this becomes a major issue? Doesn't sound serious yet...

 

[vogon13]

Software or hardware issue? If engine mistakenly programmed to burn for too short a time, no problem, hopefully.<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[erioladastra]

Not a programming issue.<br /><br />There is no critical rush (i.e., ISS won't be reentering soon) but it is required for phasing for 20P.

 

[radarredux]

I missed the SDC article that includes more information.<br /><br />http://www.space.com/missionlaunches/051019_exp12_issreboost.html<br /><br />There is just a little bit more info (with more links) at Slashdot:<br /><br />http://science.slashdot.org/science/05/10/19/1449246.shtml?tid=160&tid=14

 

[radarredux]

> <i><font color="yellow">The HeavensAbove site gives the plot.</font>/i><br /><br />Looks like a stock chart.<br /><br />Why are the highs and lows between cycles getting lower each time? For example, it looks like there were high points last October, mid January, and early July, but each high point was lower than the previous one. Likewise, there were low points in mid January, late June, and now, and each low point was lower than the previous low point.</i>

 

[nacnud]

Lowest points probably co-inside with STS docks, planned or actual.

 

[radarredux]

> <i><font color="yellow">Lowest points probably co-inside with STS docks, planned or actual.</font>/i><br /><br />But they keep getting lower each time. It doesn't seem like a good trend line.</i>

 

[CalliArcale]

As long as they don't get too low, it's not a problem. They may be allowing the station to get lower because of the planned resumption of shuttle flights; the Shuttle can't make as high an altitude as Soyuz can (at that particular orbital plane, anyway) with sufficient safety margins. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[ace5]

The old Soyuz (7K-OK and 7K-T) had two engines (one was the back-up). From Soyuz T onwards the back-up was deleted, since for deorbit they could simply use the DPO thrusters.<br />Progress has never such a backup engine, and this means that there is no high thrust engine left for orbit maintenance if the sole engine fails. More: Progress M-17 broke the mission time for Progress spacecraft record by staying aloft for 317+ days because its engine malfuntioned, and the attitude trhusters didnt had the force to deorbit it (due to its higer orbit at that time, I think).<br />I guess that they could use the attitude sontrols thrusters for orbit altitude maintenance, or simply jettison M-54 and wait for M-55 dock to do the job.

 

[erioladastra]

"I guess that they could use the attitude sontrols thrusters for orbit altitude maintenance, or simply jettison M-54 and wait for M-55 dock to do the job"<br /><br />No real worry. Progress has 8 thrusters - 4 used for the big lift and 4 which pulse to maintain the CG during the big burn. It was these 4 pulsing thrusters that lost communication with the computer and shut down. My guess is that if they can't fix that, the solution would be more frequent, smaller burns with the other thrusters.

 

[ace5]

erioladastra:<br /><br />"No real worry. Progress has 8 thrusters - 4 used for the big lift and 4 which pulse to maintain the CG during the big burn. It was these 4 pulsing thrusters that lost communication with the computer and shut down. My guess is that if they can't fix that, the solution would be more frequent, smaller burns with the other thrusters. "<br /><br />Oh, so, that´s all OK.<br /><br />A little correction: I think that, since the Progress M Propulsion Compartment (PAO) is derived from Soyuz TM, it has 14 DPO-B thrusters with 13,5 kg thrust and 12 DPO-M thrusters with 2,5 kg thrust for its attitude control. <br />I think that these smaller engines are the used to CG control, like you said.<br /><br />I remember that if these smaller engines fails, separation still can be achieve by using only springs, located on the docking apparatus.<br />Improved versions of these engines are used on Zvezda.

 

[erioladastra]

ace5 - yes, you are correct. I was just refering to that 8 were nominally to be used for the reboost. But yes, there are also other thrusters not to mention the SM engines...

 

[ace5]

erioladastra<br /><br />It is interesting that orbital mechanics allow vehicles to rely sometimes on so small-thrust motors for orbital maintenance. Remember Skylab? It lacked any huge motors, just small thursters, acting together with Apollo´s CSM (also small) engines. And I dont think that any SPS main engine firings were made on Apollo-Skylab flights.<br /><br />I remember that old spacestation Salyut 7´s orbit was almays been *lowered* before a 3-person Soyuz T be launched, because Soyuz T couldnt reach the station in a higher than 400 km orbit carrying 3 people inside!<br />For a 2-crew Soyuzn T this procedure was not needed.<br />Salyut could rely on their own 400-kg 2-main thrusters for orbit correction, but Soyuz and Progress firings were also used to maintan orbit.