Arm on standby for Discovery

[jamesm]

ShuttleDiscovery - 28/6/2007  2:45 PM

gordo - 27/6/2007  11:53 PM

if you read through the manifest there have been 5 Canadarms. 201, 202, 301, 302 (destroyed on Challenger), and 303.

So which 3 canadarms are in use today? 202, 301 and 303?

Yes.  Btw: we built one arm for each orbiter 4 in all. When one was lost on Challenger, it was decided not to replace it, just use move one of the arms around to meet manifest requirements - there were spares for the first arm, such as end Effector 202.  Reason was that there were qualification concerns with the EEs related to life.

Also; someone asked - there are 3 OBSS- one for each arm

[Rocket Guy]

I don't get it though, the CSA site specifically says in a couple of places that they delivered a new arm after Challenger. You are saying they are totally wrong?

I'm also a little confused by saying that 202 is not an arm, rather a spare end effector.

What is meant when it says STS-115 and others flew with arm 202?

[collectSPACE]

Ben - 29/6/2007  1:32 PM

I'm also a little confused by saying that 202 is not an arm, rather a spare end effector.

I guess I am confused by this as well, especially seeing as though CSA identifies arm 201 flying after arm 202 is in service. Are the arms' IDs based on the end effector only?

[gordo]

Maybe parts from an arm were used to build the 3rd OBSS, as originally there were only plans for 2 OBBS'

[gordo]

Knew this was around somewhere

Moving on to the production of a third IBA, NASA will use some of the currently available hardware to make up the new boom.

'A 3rd OBSS Sensor Package 1 is in development and can be completed under the OBSS sustaining engineering budget. A 3rd OBSS Sensor Package 2 has already been delivered. A 3rd IBA will need to be developed. Use spare SRMS booms. Total number of SRMS units will be reduced from four to three.'

[Rocket Guy]

If one SRMS was used to make an OBSS, then there were indeed four arms (five total) as stated on the CSA site. Now there are three, if that is the case.

[jamesm]

Ben - 29/6/2007  5:57 PM

If one SRMS was used to make an OBSS, then there were indeed four arms (five total) as stated on the CSA site. Now there are three, if that is the case.

Not correct.  We had several spare arm booms available from the past.  We didn't take any arm apart to make an OBSS In fact, that is why we were able to build the first OBSS so quickly to support return to flight.  I shud know - I work for MDA at the Brampton facility - the home of the Canadarms and the MSS.

[collectSPACE]

jamesm - 30/6/2007  11:34 AM

I shud know - I work for MDA at the Brampton facility - the home of the Canadarms and the MSS.

Since you are there, can you help make sense of a few statements on MDA's own website that seem to contradict the information that there were only four arms? On MDA's website they write:

Canadarm was designed, developed and built by MDA, under contract to the National Research Council of Canada. The first arm was Canada's contribution to NASA's Space Shuttle Program. Subsequently, NASA ordered four additional units which have resulted in over $900 million in export sales for Canada.

This seems to clearly state that there were five arms: one original and four more ordered by and sold to NASA. If there are only three arms in use today, and one was lost on Challenger, what happened to the fifth?

And as raised earlier, the Canadian Space Agency also distinguishes between five arms (201, 202, 301, 302, 303) in multiple places on their website, and they state:

Five Canadarms were built and delivered to NASA on April 1981, January 1983, December 1983, March 1985, and August 1993. The arms on the three shuttles in service—Discovery, Atlantis and Endeavour—are still being used.

So how do we rectify your own statements that there were only four arms and what both MDA and CSA seem to be promoting to the public?

[Rocket Guy]

You keep stating we are wrong but you are not saying much else. You are implying that the CSA website and others are completely wrong. A google search on the arms reveals nothing but five arms being built and four being left after Challenger, with all four making separate flights. In addition, I found a NASA/MDA Robotics press release from 2000 about the continued use of the four shuttle arms in ISS assembly; "The Canadarm, a hallmark of Canadian technology, has been a key Shuttle component since it first entered service in 1981. The four Canadarms are now entering a very busy phase with the on-orbit assembly of the International Space Station."

I also still do not understand why arm 202 is distinguished; how all four numbers are listed as making flights in the past decade; and how the end effector is its own designation.

If you could please elaborate in detail, it would really help. Perhaps the CSA and other websites need to be corrected?

[ShuttleDiscovery]

I'm also confused! After just being on the CSA website the fact that there were five arms does seem to be the case as all four remaining seem to have been in service within the past 5 years...

EDIT: Altough you can't exactly trust Wikipedia, even that states there are 5 arms and has a link to the same CSA page.

[gordo]

This is the Topic where the miniboom was delted in favor of a 3rd OBSS
http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=5127&posts=1&start=1

Like most major aerospace components, the items exist in paper form; eg RMS 201, could likely be built up now of overhauled parts that have flown on other RMS'.  So a 4th Arm is retired from the flight inventory and component parts retunred to the spares inventory after overhaul.   Some of the boom components that were either spares of from the now unused arm would be the ones then re-used on the 3rd OBSS.

With these parts used, it could be hard for MDA to still support 4 arms.  With only 3 orbiters needing 3 arms, its an easy decision to retire one

[ShuttleDiscovery]

Thanks for that Gordo