Boeing Starliner (CST-100) CFT mission discussion thread : May-September 2024

[Lee Jay]

My own uninformed opinion is that NASA cannot realistically evaluate this flight as meeting the CFT completion milestone of the contract, and also cannot certify Starliner for crewed CCP operations.

Haven't the service module thrusters been problematic on every flight so far?

I think we've been told that. Does this mean you think NASA should not have accepted OFT-2 for the OFT milestone?

I was just trying to remember.

If they didn't find and correct the root cause of the issues, then it shouldn't have flown again until they did.  It certainly shouldn't fly again after this flight until a redesign and modification or rebuild of the propulsion systems having issues, which appears to be at least two things - the helium supply system and the thruster doghouses.

I'm not sure how many SMs have been built and outfitted already, but a re-design could be expensive, problematic and lengthy especially if they are already built.

At today's press conference, NASA (Stich?) said that redesign is one alternative, but changing the way the thrusters are used is another alternative and is preferred because it's quicker and less expensive. The tone of voice said to me that redesign would put the schedule and possibly the program at risk, but I admit that I'm reading an awful lot into a tone of voice.

They can't do just that.  At the last one, they admitted that they don't understand why the doghouse is so much hotter than predicted.  At the very least, they have to understand that before they fly again so they at least know where to put the limits on firings (frequency/duration/starting temperature).  That's if they don't re-design to fix whatever is causing those unexpectedly high temperatures.

I think that they more or less said that. They must figure out exactly what happens before they can know what limits to impose. That leads to another question: will NASA accept Boeing's simulation model, or will further actual tests be needed? And that leads to yet another question: can those tests be done on the ground, or will another space flight be needed? Ground testing of a full doghouse would be really hard.

Can you test thrusters in a thermal vacuum chamber?  Hydrazine, combustion products....sounds icky.

[ImperfectSense]

It begs another question in my mind.... was Butch deliberately "over-using" the thrusters?  Or was his use dictated by what he felt he needed in order to control the spacecraft?  Tuning software to use the thrusters less is one thing, but when you are talking about HUMAN piloting... how exactly do you implement those limits?  It seems like designing a NASCAR car and then telling the driver "If you turn left too much or too quickly your steering will fail".  Like... wtf?

[JayWee]

It begs another question in my mind.... was Butch deliberately "over-using" the thrusters?  Or was his use dictated by what he felt he needed in order to control the spacecraft?  Tuning software to use the thrusters less is one thing, but when you are talking about HUMAN piloting... how exactly do you implement those limits?  It seems like designing a NASCAR car and then telling the driver "If you turn left too much or too quickly your steering will fail".  Like... wtf?

Have thermal limit model, cycle through thrusters, show heatbar, stop thrusting ...

It's something I'm also curious about. A simple "ok, astro pushes thrust Z+ indefinitely, let's see what happens". Although I guess the heating might come from unanticipated interactions of multiple thrusters.

[DanClemmensen]

I think that they more or less said that. They must figure out exactly what happens before they can know what limits to impose. That leads to another question: will NASA accept Boeing's simulation model, or will further actual tests be needed? And that leads to yet another question: can those tests be done on the ground, or will another space flight be needed? Ground testing of a full doghouse would be really hard.

Can you test thrusters in a thermal vacuum chamber?  Hydrazine, combustion products....sounds icky.

You can test one thruster that way, and they did so, especially after the issues arose during CFT. Several forum postsz have stated that you cannot easily test a doghouse full of thrusters in a vacuum chamber.

[Comga]

I thought it had been said previously that since these initial flights are NASA test flights (vs. 'commercial' such as the regular flights will be) the FAA licensing is much simpler or not even required.

SpaceX’s reentry license RLO-20-007 was issued 11/13/2020 (and expiring 11/13/2024) ten months before Inspiration 4 on 9/16/21 but a half year after CFT’s equivalent Demo 2 launch and 8 years after the launch if CRS-1.   
That’s compatible with only fully commercial (not NASA “commercial” services) reentries needing FAA permits.

[laszlo]

... It seems like designing a NASCAR car and then telling the driver "If you turn left too much or too quickly your steering will fail".  Like... wtf?

It's common in engineering to have the operators modify procedures to compensate for physical limitations since it's cheaper and faster than modifying and requalifying hardware, even in race cars. If you've seen the movie "Ford vs. Ferrari" (supposedly technically accurate) that's exactly what they were doing with brake fades and RPM reductions.

[deltaV]

... It seems like designing a NASCAR car and then telling the driver "If you turn left too much or too quickly your steering will fail".  Like... wtf?

Instructions that operators must not use a control too much or catastrophe will occur are actually fairly common in transport. Rules like that inevitably cause crashes sometimes when operators mess up so they aren't ideal but it's sometimes hard to avoid them. Many examples follow.

Relatively tall road vehicles such as SUVs and trucks may roll over if one steers too aggressively at high speed.

Vehicles and boats with manual transmissions can often be damaged by shifting at high throttle.

Using the full control authority of an airplane above maneuvering speed (https://en.wikipedia.org/wiki/Maneuvering_speed) may cause airframe failure. Even below maneuvering speed, repeated use of the controls can cause airframe failure, e.g. https://en.wikipedia.org/wiki/American_Airlines_Flight_587, as can using the full control authority of multiple axes at once.

Trains can be damaged by increasing the throttle too quickly when starting out. Cargo train brakes will fail if applied and released too often before they can recharge.

[Surfdaddy]

... It seems like designing a NASCAR car and then telling the driver "If you turn left too much or too quickly your steering will fail".  Like... wtf?

Instructions that operators must not use a control too much or catastrophe will occur are actually fairly common in transport. Rules like that inevitably cause crashes sometimes when operators mess up so they aren't ideal but it's sometimes hard to avoid them. Many examples follow.

Relatively tall road vehicles such as SUVs and trucks may roll over if one steers too aggressively at high speed.

Vehicles and boats with manual transmissions can often be damaged by shifting at high throttle.

Using the full control authority of an airplane above maneuvering speed (https://en.wikipedia.org/wiki/Maneuvering_speed) may cause airframe failure. Even below maneuvering speed, repeated use of the controls can cause airframe failure, e.g. https://en.wikipedia.org/wiki/American_Airlines_Flight_587, as can using the full control authority of multiple axes at once.

Trains can be damaged by increasing the throttle too quickly when starting out. Cargo train brakes will fail if applied and released too often before they can recharge.

Okay, so that means that either the crew exceeded limitations after launch and during ISS approach, or there were no limits set by Boeing, or that Boeing set the wrong limits. All possibilities are bad.

Does anybody know what the comparable Shuttle situation was? Were there RCS limits for attitude control firings? Or some display/warning when they were approaching a limit? Or was the Shuttle much more robust in this area?

[xyv]

Wait a minute, wasn't butch using manual controls so that NASA and Boeing could conduct tests of thrusters that had already gone off line?  I remember them testing an bringing 4 of 5 thrusters back while Butch did manual station keeping.  After they were done, they had the audacity to ask Butch to do the manual flight demosntration part of the mission and he replied something to the effect that "...he considered the unexpected manual flying to have fulfilled that test's objectives...".  After they docked I remember thinking Butch was in so many words saying "you want me to put further stress on this already damaged test craft?...aborting to a safe harbor..."

[ImperfectSense]

Wait a minute, wasn't butch using manual controls so that NASA and Boeing could conduct tests of thrusters that had already gone off line?  I remember them testing an bringing 4 of 5 thrusters back while Butch did manual station keeping.  After they were done, they had the audacity to ask Butch to do the manual flight demosntration part of the mission and he replied something to the effect that "...he considered the unexpected manual flying to have fulfilled that test's objectives...".  After they docked I remember thinking Butch was in so many words saying "you want me to put further stress on this already damaged test craft?...aborting to a safe harbor..."

I recall the same, although my interpretation of Butch's comment was that it also contained some degree of "Our human brains are getting tired because we have been using them quite extensively, we are not going to risk introducing more opportunities for human error than we have to."

[whitelancer64]

My own uninformed opinion is that NASA cannot realistically evaluate this flight as meeting the CFT completion milestone of the contract, and also cannot certify Starliner for crewed CCP operations.

Haven't the service module thrusters been problematic on every flight so far?

I think we've been told that. Does this mean you think NASA should not have accepted OFT-2 for the OFT milestone?

I was just trying to remember.

If they didn't find and correct the root cause of the issues, then it shouldn't have flown again until they did.  It certainly shouldn't fly again after this flight until a redesign and modification or rebuild of the propulsion systems having issues, which appears to be at least two things - the helium supply system and the thruster doghouses.

I'm not sure how many SMs have been built and outfitted already, but a re-design could be expensive, problematic and lengthy especially if they are already built.

For OFT-1 the primary problem was the mission clock telling Starliner that it was in a different phase of flight than it actually was, causing it to fire its OMAC thrusters much longer than it was supposed to, putting it in the wrong orbit and draining so much fuel it could not rendezvous with the ISS. I don't recall if any thrusters failed as a result.

On OFT-2, two of the large OMAC thrusters failed during the orbital insertion burn, one after just one second and another one after firing for about 25 seconds. Both were in the same doghouse. Starliner automatically switched to other thrusters to compensate. Additionally, two RCS thrusters shut down during the ISS rendezvous, but that had no impact on the docking. All four shutdowns were due to low chamber pressure. I don't remember if they recovered any of those thrusters, but Starliner did its deorbit burn and reentry without drama.

[sdsds]

[...]I don't remember if they recovered any of those thrusters, but Starliner did its deorbit burn and reentry without drama.

Thanks for the (elided) summary! During nominal ascent or on-orbit operations are the RCS thrusters on the Starliner capsule ever used, or only thrusters on the service module?

[ChrisC]

Quotes from the updates thread here:

Link for NASA press conference:  https://youtube.com/watch?v=U7_lH5kg8Yo (before the event)

the youtube feed never started

the youtube feed finally started

Since many of us missed the opening remarks at the press conference, can someone post a link to a full archive when it is available.  The full press conference lasted about 45 minutes.

NASA has finally uploaded the full presser on their "NASA Video" YouTube channel.  https://youtube.com/watch?v=B09kIoR9k5E Starts at 1:00.

Just to state it plainly and for the record, NASA PAO really shanked it this time.  The original Youtube link they provided ahead of time, that many of us were monitoring, didn't actually get going until a good 20 minutes into the presser.  Those us who were not able to watch live, rather planned to catch up later, went to the "live" section of the NASA Video channel on Youtube to watch the archived recording but found nothing newer than a presser from three weeks ago.  Eventually it popped up in the "videos" (pre-recorded videos) section of that Youtube channel, which is not a place we normally look for this kind of live content.

So the point of this post is to wag a finger at NASA PAO and ask them to do better next time   Hopefully this is not a sign of how things will go in this new "NASA Plus" era after the shutdown of NASA TV on satellite (the 24/7 feed to cable systems).  If you're not going to offer linear TV anymore, then you need to get better at non-linear. Procedures, checklists, monitoring -- come on, be pros, do the things.

[SoftwareDude]

Is the undocking going to be covered live? They cover the undocking of everything else, including uncrewed cargo.

[Jorge]

Is the undocking going to be covered live? They cover the undocking of everything else, including uncrewed cargo.

Posted on the update thread, 33 minutes before you asked.

[kdhilliard]

... During nominal ascent or on-orbit operations are the RCS thrusters on the Starliner capsule ever used, or only thrusters on the service module?

No.  The Crew Module (CM) RCS thrusters still have their covers in place, so they do not appear to have been used prior to docking.
(Photo from June 13.)
The 12 CM jets are Aerojet Rocketdyne 100 lbf (440 N) MR-104J hydrazine monopropellant engines used to "properly orient the spacecraft during atmospheric re-entry" (per AJR release).
Photo of MR-104J from https://www.satcatalog.com/component/mr-104j-440n/

Those thrusters have been mentioned twice during CFT NASA news conferences.
* Once was when a reporter asked if NASA was concerned about their reliability given the issues with the SM RCS thrusters, and Steve Stich said no, because the were of a different, monopropellant design.
* And back when a late June return was still expected, NASA Flight Director Mike Lammers mentioned them while describing the return timeline.  2024-06-18 presser at 40:14

After the undock, Starliner departs a lot quicker than at rendezvous.  It will back down the V-bar in front of Station.  26 minutes later it will do a burn and it will do what we call a quarter lap.  It will go up and above the space station and at the very Zenith of Station, at 41 minutes after undocking, it will do what we call the departure initiation burn.  That will send it out and away, and it will start phasing below Space Station.  As that happens, the vehicle will do an automated hot fire test of the Crew Module propulsion system.  Just a reminder, the Service Module that we've been talking about, is used for rendezvous and undocking, but the Service Module is jettisoned after the deorbit burn and burns up in the Pacific.  The Crew Module propulsion system is actually what does re-entry.  So we hot fire those Jets.  It's a monopropellant system.  It needs a bit of conditioning.  And also we want to make sure that all Jets and both manifolds are working for entry.  So we'll go ahead and do that just after we depart from ISS.

The CM propulsion system hot fire test was not mentioned during Wednesday's description of the current modified station departure plan, but it will presumably be conducted at a similar time.

I was disappointed that no one asked what the contingency plan was if that hot fire test failed (the first test of that system this flight).
My *guess* is that, if crewed, Starliner would return to Station, but being uncrewed, it would not.

[clongton]

I was disappointed that no one asked what the contingency plan was if that hot fire test failed (the first test of that system this flight).
My *guess* is that, if crewed, Starliner would return to Station, but being uncrewed, it would not.

There is no contingency plan. I believe that the hot fire test doesn't happen until after the service module has executed the deorbit burn and is jettisoned. If the test were to fail, the crew could NOT return to the station. They are committed to a reentry with malfunctioning command module thrusters. There is no way back. The crew is in extreme jeopardy and might not survive reentry, depending on the severity of the malfunction.
This is, in my opinion, an unforgivable design flaw in Starliner.

[kdhilliard]

I was disappointed that no one asked what the contingency plan was if that hot fire test failed (the first test of that system this flight).
My *guess* is that, if crewed, Starliner would return to Station, but being uncrewed, it would not.

There is no contingency plan. I believe that the hot fire test doesn't happen until after the service module has executed the deorbit burn and is jettisoned. If the test were to fail, the crew could NOT return to the station. ...

No.  The CM propulsion system hot fire test was very specifically described as occurring after the departure initiation burn, but well before deorbit burn.  At that point return to station would not be a problem, assuming the SM jets were still operable.  (Today, without crew onboard, a return wouldn't make much sense.)

[clongton]

I was disappointed that no one asked what the contingency plan was if that hot fire test failed (the first test of that system this flight).
My *guess* is that, if crewed, Starliner would return to Station, but being uncrewed, it would not.

There is no contingency plan. I believe that the hot fire test doesn't happen until after the service module has executed the deorbit burn and is jettisoned. If the test were to fail, the crew could NOT return to the station. ...

No.  The CM propulsion system hot fire test was very specifically described as occurring after the departure initiation burn, but well before deorbit burn.  At that point return to station would not be a problem, assuming the SM jets were still operable.  (Today, without crew onboard, a return wouldn't make much sense.)

Here’s a detailed timeline of the Starliner’s mission sequence from undocking to landing according to several sources:

Pre-Undocking (hours before undocking):
Final checks are performed on the spacecraft’s systems, weather at the landing sites, and the service module’s thrusters.

Undocking from the ISS:
Starliner initiates undocking from the ISS using the service module’s Reaction Control System (RCS) thrusters, which are tested during this phase to confirm their performance.
The spacecraft slowly backs away from the ISS and enters free flight

Orbit Adjustment (post-undocking):
Starliner continues to use its service module thrusters to adjust its position and distance from the ISS. The spacecraft moves into a stable orbit in preparation for deorbiting.

Deorbit Burn:
Approximately 60 minutes before landing, Starliner performs a deorbit burn using the service module’s engines. This critical burn slows the spacecraft and commits it to re-entry.

Service Module Separation:
After the deorbit burn, the service module is jettisoned to burn up in the atmosphere. The command module, which contains the crew (or cargo in uncrewed missions), continues on its re-entry trajectory​.

First Command Module Thruster Test (after service module separation):
Once the service module is jettisoned, the command module’s thrusters are tested for the first time. These thrusters help orient and stabilize the command module as it prepares for re-entry into Earth’s atmosphere​.

Atmospheric Re-entry:
Starliner experiences temperatures up to 3,000°F as it re-enters the atmosphere. A communications blackout occurs due to plasma buildup, lasting approximately 4 minutes​.

Parachute Deployment:
After re-entry, Starliner deploys a series of parachutes to slow its descent:
First, two drogue parachutes are deployed.
Then, three main parachutes are deployed to further reduce speed​.

Airbag Deployment:*
As the spacecraft approaches the ground, it jettisons the heat shield and inflates its landing airbags to cushion the impact. The airbags deploy just before touchdown to ensure a safe landing for the crew or cargo​.

Landing:
Starliner lands at one of the predetermined landing sites, such as White Sands, NM, or Dugway Proving Ground, UT. Recovery teams approach the capsule, ensuring the area is safe from any unburned hypergolic fuels, and prepare the spacecraft for crew exit or cargo unloading​.

*Edited to include heat shield jettison.

[litton4]

One small addition, they jettison the heat shield while on the parachutes, as the air bags are stored behind this, so could not deploy if it were still in place....