NASA - Europa Clipper updates and discussion

[jbenton]

Is clipper user the older style of reaction wheel (The article mentions wearing out). Isn't there a newer style of reaction wheel that is thought to have less wear issues?

The problematic Ithaco reaction wheels that repeatedly suffered increases in bearing friction on several disparate
[snip]

I wasn't thinking about the problem batch that affected kepler, dawn, and such. I thought I'd heard that was a newer type of wheel developed a few years ago with less failure points.

I think you're talking about using ceramic, rather than metal ball bearings in the reaction wheels. I asked a similar question on one of the JWST threads about 5 four years ago, I'm going to post the responses I got from that, but first a summary:
Basically, Ithaco solved their problem and determined the solution was to use ceramic rather than metal bearings. However, another supplier - Teldix/RCD (Rockwell Collins Deutschland) - (apparently) never had those problems in the first place. It wasn't clear from the answers I got what Teldix was doing right and whether ceramic bearings were involved. My understanding is that Ithaco will now only use ceramic bearings. Either way, I'd conclude that if 'Clipper is getting reaction wheels from either Ithaco or Teldix, we can trust them.   

The full nested quote conversation (minus the Scott Manley video I included in the first post) is here (don't worry, it's short). My first post, including the video - in case you havent' watched it already and want to know the science behind the bearings issue - is here.
EDIT: I'd quote that conversation directly here, but that thread has since been locked.

[jbenton]

Space.com posted an article stating instrument delays might affect launch.

The article: Europa Clipper instrument delays worry scientists eyeing 2024 launch

[snip]
"The ATLO people have expended all of their magic," Niebur said. "Any further delay is going to eat directly into the schedule margin we have."

Does anyone know how much schedule margin they have? A few months?

[vjkane]

Space.com posted an article stating instrument delays might affect launch.

The article: Europa Clipper instrument delays worry scientists eyeing 2024 launch

[snip]
"The ATLO people have expended all of their magic," Niebur said. "Any further delay is going to eat directly into the schedule margin we have."

Does anyone know how much schedule margin they have? A few months?

At the Planetary Advisory Committee meeting today, Planetary Science Division chief Glaze had just one slide on Clipper with the message that the team is working hard but making deliveries. This was a meeting for delivering tough news on the planetary program, and she did for a number of programs. (For example, she said that she thought that the problems uncovered at JPL are likely present at other centers, too.)

This doesn't mean that either view is wrong. Having followed a number of missions, I think that many are on the edge right up to launch (been several good books on Mars missions of the last of decades that go into detail). Clipper may be on the edge, but there's normal on the edge and crisis on the edge.

[LouScheffer]

Is clipper user the older style of reaction wheel (The article mentions wearing out). Isn't there a newer style of reaction wheel that is thought to have less wear issues?

The problematic Ithaco reaction wheels that repeatedly suffered increases in bearing friction on several disparate spacecraft, correlated with solar alpha events, were redesigned some years ago to use ceramic ball bearings that wouldn't be subject to the theorized root cause, and the problem has not recurred with these units. Ithaco is now part of Raytheon.

But that saga does show that the aerospace supply chain can be a small world, and one flawed component design can find its way into all sorts of missions. By the time Kepler launched, NASA was well aware of the anomalies, and they sent the reaction wheels for additional pre-launch testing (no issues found), but obviously they didn't select an alternative supplier and launched with the flawed reaction wheels that failed.

I wasn't thinking about the problem batch that affected kepler, dawn, and such. I thought I'd heard that was a newer type of wheel developed a few years ago with less failure points.

The story I heard (during the time when reaction wheels were failing) is that there are $10⁵ reaction wheels and $10⁶ reaction wheels.  (Perhaps mechanical bearings vs non-contact suspension?)  The expensive wheels were known reliable but scientific missions such as Kepler could not afford them and had to use the less expensive wheels, which were the ones that developed problems.  However, as mentioned above, it seems the problem with lower cost versions was arcing of cosmic-ray induced charges across the steel balls of the bearings, causing failure.  Ceramic ball bearings seems to have fixed this issue.

So either way Clipper should be OK.  With its bigger budget, it might be using the expensive wheels.  Even if it's using the less expensive wheels, the problems seem to be fixed.

[Star One]

Is clipper user the older style of reaction wheel (The article mentions wearing out). Isn't there a newer style of reaction wheel that is thought to have less wear issues?

The problematic Ithaco reaction wheels that repeatedly suffered increases in bearing friction on several disparate spacecraft, correlated with solar alpha events, were redesigned some years ago to use ceramic ball bearings that wouldn't be subject to the theorized root cause, and the problem has not recurred with these units. Ithaco is now part of Raytheon.

But that saga does show that the aerospace supply chain can be a small world, and one flawed component design can find its way into all sorts of missions. By the time Kepler launched, NASA was well aware of the anomalies, and they sent the reaction wheels for additional pre-launch testing (no issues found), but obviously they didn't select an alternative supplier and launched with the flawed reaction wheels that failed.

I wasn't thinking about the problem batch that affected kepler, dawn, and such. I thought I'd heard that was a newer type of wheel developed a few years ago with less failure points.

The story I heard (during the time when reaction wheels were failing) is that there are $10⁵ reaction wheels and $10⁶ reaction wheels.  (Perhaps mechanical bearings vs non-contact suspension?)  The expensive wheels were known reliable but scientific missions such as Kepler could not afford them and had to use the less expensive wheels, which were the ones that developed problems.  However, as mentioned above, it seems the problem with lower cost versions was arcing of cosmic-ray induced charges across the steel balls of the bearings, causing failure.  Ceramic ball bearings seems to have fixed this issue.

So either way Clipper should be OK.  With its bigger budget, it might be using the expensive wheels.  Even if it's using the less expensive wheels, the problems seem to be fixed.

What so they picked wheels just because they saved one dollar each on them. Mind you from my own experience of the public sector and budgeting maybe I am not that surprised.

[edzieba]

Is clipper user the older style of reaction wheel (The article mentions wearing out). Isn't there a newer style of reaction wheel that is thought to have less wear issues?

The problematic Ithaco reaction wheels that repeatedly suffered increases in bearing friction on several disparate spacecraft, correlated with solar alpha events, were redesigned some years ago to use ceramic ball bearings that wouldn't be subject to the theorized root cause, and the problem has not recurred with these units. Ithaco is now part of Raytheon.

But that saga does show that the aerospace supply chain can be a small world, and one flawed component design can find its way into all sorts of missions. By the time Kepler launched, NASA was well aware of the anomalies, and they sent the reaction wheels for additional pre-launch testing (no issues found), but obviously they didn't select an alternative supplier and launched with the flawed reaction wheels that failed.

I wasn't thinking about the problem batch that affected kepler, dawn, and such. I thought I'd heard that was a newer type of wheel developed a few years ago with less failure points.

The story I heard (during the time when reaction wheels were failing) is that there are $10⁵ reaction wheels and $10⁶ reaction wheels.  (Perhaps mechanical bearings vs non-contact suspension?)  The expensive wheels were known reliable but scientific missions such as Kepler could not afford them and had to use the less expensive wheels, which were the ones that developed problems.  However, as mentioned above, it seems the problem with lower cost versions was arcing of cosmic-ray induced charges across the steel balls of the bearings, causing failure.  Ceramic ball bearings seems to have fixed this issue.

So either way Clipper should be OK.  With its bigger budget, it might be using the expensive wheels.  Even if it's using the less expensive wheels, the problems seem to be fixed.

What so they picked wheels just because they saved one dollar each on them. Mind you from my own experience of the public sector and budgeting maybe I am not that surprised.

Those are powers (10^5 & 10^6), not digits.

[Barley]

The story I heard (during the time when reaction wheels were failing) is that there are $10⁵ reaction wheels and $10⁶ reaction wheels.

What so they picked wheels just because they saved one dollar each on them. Mind you from my own experience of the public sector and budgeting maybe I am not that surprised.

That's a savings of $900,000 per wheel not $1 per wheel.

In the very long term it would make sense to risk a few missions to save several million per mission on many later missions.  Or perhaps dedicate engineering flights to cost reduction.

[LouScheffer]

The story I heard (during the time when reaction wheels were failing) is that there are $10⁵ reaction wheels and $10⁶ reaction wheels.

What so they picked wheels just because they saved one dollar each on them. Mind you from my own experience of the public sector and budgeting maybe I am not that surprised.

That's a savings of $900,000 per wheel not $1 per wheel.

And they need at least 4 wheels (for the spacecraft) and I suspect 4 more for the "iron bird" engineering model.  That's at least $3.6M and likely $7.2M.  That's a significnnt chunk of any but the most well-funded missions.

[vjkane]

The story I heard (during the time when reaction wheels were failing) is that there are $10⁵ reaction wheels and $10⁶ reaction wheels.

What so they picked wheels just because they saved one dollar each on them. Mind you from my own experience of the public sector and budgeting maybe I am not that surprised.

That's a savings of $900,000 per wheel not $1 per wheel.

And they need at least 4 wheels (for the spacecraft) and I suspect 4 more for the "iron bird" engineering model.  That's at least $3.6M and likely $7.2M.  That's a significnnt chunk of any but the most well-funded missions.

And they may want to have a couple spares to swap in if testing shows problems with any of the installed units.

[Star One]

Is clipper user the older style of reaction wheel (The article mentions wearing out). Isn't there a newer style of reaction wheel that is thought to have less wear issues?

The problematic Ithaco reaction wheels that repeatedly suffered increases in bearing friction on several disparate spacecraft, correlated with solar alpha events, were redesigned some years ago to use ceramic ball bearings that wouldn't be subject to the theorized root cause, and the problem has not recurred with these units. Ithaco is now part of Raytheon.

But that saga does show that the aerospace supply chain can be a small world, and one flawed component design can find its way into all sorts of missions. By the time Kepler launched, NASA was well aware of the anomalies, and they sent the reaction wheels for additional pre-launch testing (no issues found), but obviously they didn't select an alternative supplier and launched with the flawed reaction wheels that failed.

I wasn't thinking about the problem batch that affected kepler, dawn, and such. I thought I'd heard that was a newer type of wheel developed a few years ago with less failure points.

The story I heard (during the time when reaction wheels were failing) is that there are $10⁵ reaction wheels and $10⁶ reaction wheels.  (Perhaps mechanical bearings vs non-contact suspension?)  The expensive wheels were known reliable but scientific missions such as Kepler could not afford them and had to use the less expensive wheels, which were the ones that developed problems.  However, as mentioned above, it seems the problem with lower cost versions was arcing of cosmic-ray induced charges across the steel balls of the bearings, causing failure.  Ceramic ball bearings seems to have fixed this issue.

So either way Clipper should be OK.  With its bigger budget, it might be using the expensive wheels.  Even if it's using the less expensive wheels, the problems seem to be fixed.

What so they picked wheels just because they saved one dollar each on them. Mind you from my own experience of the public sector and budgeting maybe I am not that surprised.

Those are powers (10^5 & 10^6), not digits.

Well that does make a lot more sense.

[edzieba]

The story I heard (during the time when reaction wheels were failing) is that there are $10⁵ reaction wheels and $10⁶ reaction wheels.

What so they picked wheels just because they saved one dollar each on them. Mind you from my own experience of the public sector and budgeting maybe I am not that surprised.

That's a savings of $900,000 per wheel not $1 per wheel.

In the very long term it would make sense to risk a few missions to save several million per mission on many later missions.  Or perhaps dedicate engineering flights to cost reduction.

At the time, it was not even a decision to 'risk a few missions': the arcing failure mode was not known, so the choice was between reaction wheels that had a design life more adequate for the intended mission lifetime, and reaction wheels that were much more expensive with a design life far beyond the intended mission lifetime.

[ccdengr]

The story I heard (during the time when reaction wheels were failing) is that there are $10⁵ reaction wheels and $10⁶ reaction wheels.  (Perhaps mechanical bearings vs non-contact suspension?)

Probably.  See "Ball bearing versus magnetic bearing reaction and momentum wheels as momentum actuators", https://ntrs.nasa.gov/citations/19800015012

Different bearing technologies of momentum actuators for the attitude control of satellites are compared and a guideline for the selection of the suitable momentum actuators or momentum actuator configurations to meet given mission goals with high reliability and low cost is developed. The comparison between ball bearing and magnetic bearing momentum actuators shows that given mission requirements can be economically met by employing the ball bearing technology without decreasing reliability and lifetime.

Admittedly this was written before some of the failures.

[Nomadd]

The story I heard (during the time when reaction wheels were failing) is that there are $10⁵ reaction wheels and $10⁶ reaction wheels.  (Perhaps mechanical bearings vs non-contact suspension?)

Probably.  See "Ball bearing versus magnetic bearing reaction and momentum wheels as momentum actuators", https://ntrs.nasa.gov/citations/19800015012

Different bearing technologies of momentum actuators for the attitude control of satellites are compared and a guideline for the selection of the suitable momentum actuators or momentum actuator configurations to meet given mission goals with high reliability and low cost is developed. The comparison between ball bearing and magnetic bearing momentum actuators shows that given mission requirements can be economically met by employing the ball bearing technology without decreasing reliability and lifetime.

Admittedly this was written before some of the failures.

That statement seems a little open to interpretation to me. "Meeting mission requirements" and "without decreasing reliability and lifetime" doesn't obviously cover the extended missions where most of the failures occur. Losing something in the third year of it's year long mission is still a loss.   Think of what we would have lost if nobody had ever gone above and beyond primary mission requirements in reliability of their systems.

[ccdengr]

"Meeting mission requirements" and "without decreasing reliability and lifetime" doesn't obviously cover the extended missions where most of the failures occur.

Fair enough, but two points:

1) In any cost-constrained mission (in my experience, all of them) nobody designs for anything more than the primary mission duration times a healthy margin (2 or 3x, typically).  A 10x cost increase is dead on arrival if all it enables is a longer extended mission.

2) The magnetic bearings have more electronics failure modes so it's not a straight lifetime trade anyway.  If you read the paper (which is from 1980 after all and could no longer be relevant) it states lower reliability for a 7-year mission for magnetics unless they have redundant electronics.

I don't think I've ever worked on a mission that had magnetic reaction wheels.  But they have nearly all had extra redundant ball bearing wheels.

[Barley]

Shades of the Deacons shay here.

When you're building millions of widgets you can and do look at the warranty data and work to make the mean time to failure and the minimum time to failure converge.

For space craft not so much.  Almost everything will last far beyond its design life.  That's not bad engineering, it's just the law of small numbers.

[FutureSpaceTourist]

https://twitter.com/EuropaClipper/status/1600982087103705090

As you watch the full Moon rise tonight, remember that Jupiter's moon Europa is about the same size. One teeny difference: Europa has an ocean of liquid water beneath its surface – with more water than all of Earth's oceans combined! http://europa.nasa.gov

[LouScheffer]

But that saga does show that the aerospace supply chain can be a small world, and one flawed component design can find its way into all sorts of missions. By the time Kepler launched, NASA was well aware of the anomalies, and they sent the reaction wheels for additional pre-launch testing (no issues found), but obviously they didn't select an alternative supplier and launched with the flawed reaction wheels that failed.

The same problem happened with the precision clocks used on navigation satellites.  There are only a few vendors of space rated atomic clocks, and Europe, India, and China all picked the same provider, and their clocks began to fail in orbit.  Even worse, the backup clocks, purposely using a different technology (rubidium vs hydrogen maser) were also made by the same vendor, and suffered similar failures. Fortunately each Galileo satellite has 4 clocks and can work with only 1, so it was in general not fatal, but it was certainly a big concern.  Eventually the root caused was found and fixed, but by that time there were a lot of defective clocks in many satellites.

[redliox]

Another instrument in the cleanroom and soon to be bolted on: MASPEX

https://twitter.com/EuropaClipper/status/1611060117193232385

Sniffing out the secrets of Europa: Europa Clipper’s mass spectrometer, MASPEX, has arrived
@NASAJPL
 for integration onto our spacecraft.

[Blackstar]

It is really hard for me to stare at a group of people wearing the bunny suits and try and figure out which ones I know based upon their eyeballs.

[redliox]

It is really hard for me to stare at a group of people wearing the bunny suits and try and figure out which ones I know based upon their eyeballs.

I've worked in medical manufacturing for a good 2 years now so I can relate 

This now makes 6 instruments at least in the same building/room as Clipper and 4 being built.  MISE seems to be the last optical instrument, the gravity experiment likely to be installed same time as the high gain antenna, and I presume the magnetometer and radar are complicated by their deployment needs (especially the latter).  Has there been any word on any instrument lagging?