Progress docks safely with Zvezda module at ISS
ISS as of today. Click for original.
In what is increasingly a worrisome procedure, Russia’s just launched Progress freighter successfully docked with the aft port of the Zvezda module at ISS this past weekend, bringing with it more than 5,000 pounds of supplies and research equipment.
The image to the right, annotated additionally by me, shows the present configuration of spacecraft at ISS. The concerns center on the stress fractures that have been found in the Zvezda hull, fractures that have caused the air leak on ISS and are believed attributable to the many dockings to the module since its launch in the late ’90s, as well as the module’s age. It was first built in the late ’80s, making it almost four decades old.
For recent dockings, NASA now closes the hatch between the Russian and American halves of the stations, just in case Zvezda experiences a catastrophic failure. The Russians seem less concerned, but nonetheless they also take extra care during dockings. It is my understanding their astronauts prepare their Soyuz capsule as a lifeboat and immediately escape during these operations.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The print edition can be purchased at Amazon or from any other book seller. If you want an autographed copy the price is $60 for the hardback and $45 for the paperback, plus $8 shipping for each. Go here for purchasing details. The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
ISS as of today. Click for original.
In what is increasingly a worrisome procedure, Russia’s just launched Progress freighter successfully docked with the aft port of the Zvezda module at ISS this past weekend, bringing with it more than 5,000 pounds of supplies and research equipment.
The image to the right, annotated additionally by me, shows the present configuration of spacecraft at ISS. The concerns center on the stress fractures that have been found in the Zvezda hull, fractures that have caused the air leak on ISS and are believed attributable to the many dockings to the module since its launch in the late ’90s, as well as the module’s age. It was first built in the late ’80s, making it almost four decades old.
For recent dockings, NASA now closes the hatch between the Russian and American halves of the stations, just in case Zvezda experiences a catastrophic failure. The Russians seem less concerned, but nonetheless they also take extra care during dockings. It is my understanding their astronauts prepare their Soyuz capsule as a lifeboat and immediately escape during these operations.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The print edition can be purchased at Amazon or from any other book seller. If you want an autographed copy the price is $60 for the hardback and $45 for the paperback, plus $8 shipping for each. Go here for purchasing details. The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
The obvious question I have is why Roscosmos doesn’t just switch Progress ships over to docking with the Prichal module. Prichal has no less than FIVE (5) docking ports available which can dock both Soyuz and Progress spacecraft.
(According to Wikipedia, four of these ports have yet to be used for a docking operationally — four times for a Soyuz, once for a Progress-M propulsion compartment. The nadir port on Prichal is the only one which has been used so far.)
The best answer I can come up with is that Progress is used for station reboosts, and this is really only possible when docked to the aft end of Zevzda. But if the leak is becoming that serious of a concern, it needs to be rethought, and NASA and the other international partners should insist that Roscosmos reconsider the Prichal option. I don’t see why it would be impossible to undock a Progress after it has been fully unloaded of its supplies and redocked to Zvezda for the sole purpose of station reboost.
P.S. One of my sentences somehow moved a clause in a confusing way whilst I was in final editing. It should read:
“According to Wikipedia, four of these ports have yet to be used for a docking operationally. The nadir port on Prichal is the only one which has been used so far — four times for a Soyuz, once for a Progress-M propulsion compartment. “
Richard M: Your point is excellent. However, doing more dockings to Zvezda just to do a reboost is a bad approach. Instead, why can’t Russia do what the U.S. is doing? Dock Progress to Prichal, and when a reboost burn is required rotate the station so that the Progress is in the right position.
There may be engineering issues preventing this, but if so it would be nice to know. NASA has now demonstrated successfully that both Dragon and Cygnus capsules can do this from the American ports. Russia should improvise similarly.
The thrust vector for a reboot should go through the center of mass of the station. To some degree misalignment can be compensated for by fitting RCS thrusters or gimbaling the reboot motor but there are limits to that.
Firing not fitting
Yeah, Tom D beat me to it. It’s a thrust vector problem. When a reboot vehicle is docked to a port along the main axis of the station, it can safely do a reboost. But there are only two such ports: Harmony forward (PMA-2), and Zvezda aft. Harmony forward is where the Dragon just did that reboost test, and where the SpaceX Deorbit Vehicle will be docked for the Deorbit burns.
That said, I grok your point about the risks of using the Zvezda aft port *at all*. But none of us have enough data to evaluate those risks.