Wednesday, September 20, 2023

SpaceX Advances the Booster Flight Count Record

On last night's Starlink Group 6-17 mission from Cape Canaveral Space Force Station, SpaceX boosted the record flight count again.  Booster B1058 flew for its 17th mission, taking the status as Fleet Leader.  B1058 flew its 16th mission just over two months ago

SpaceX launched its 67th rocket of the year on Tuesday night, a staggering total for the company and its workhorse booster, the Falcon 9. At this pace, a clip of one launch every four days, the company is likely to launch 90 or more rockets during this calendar year.

The liftoff was Tuesday night at 11:38 PM EDT and looked like their wonderfully routine, nearly boring missions.  Booster B1058 had previously flown 11 previous Starlink missions along with GPS III-3, Turksat 5A, Transporter-2, Intelsat G-33/G-34, and Transporter-6.   

In the early days of the Falcon 9, it seemed to be thought that they could fly 10 times without "major refurbishment" - whatever that means.  Now that the 10 flight barrier has been broken many times, that's open for reconsideration.

SpaceX performed a fairly significant assessment of booster wear and tear after its first Falcon 9 stages reached 15 flights, and the company's engineers now believe the rockets can achieve at least 20 flights. Remarkably, SpaceX has been able to push the limits of booster reuse while maintaining a 100 percent record of success across the Falcon 9 rocket's last 228 launches, dating to a pad explosion in September 2016.

As part of its maintenance process, SpaceX still does some basic inspections and replaces engines and other critical components from time to time. Additionally, the company only risks its own internally built Starlink satellites on the most experienced boosters, reserving rockets with less mileage for its customers.

My own take on it (FWIW) is that there probably isn't one convenient number like 10, 20 or any other number.  Parts do fail, but space-rated hardware is supposed to be the best and most reliable parts money can buy.  Perhaps they should institute some sort of cost-tracking that says when the parts that have been replaced in a booster reach some percentage of the cost of making a new one, they should replace it.  I just have no idea what that point should be.  I have to believe that they already do something similar and if every booster needs a certain part replaced by the tenth flight, they'll redesign the part or re-specify it so that it lasts longer.

Moving the launch webcasts from the SpaceX website and YouTube to being on X probably reflects Elon Musk's tendency to think launch webcasts are not worth wasting time or effort on.  His attitude is largely that no one hosts a webcast when an airplane takes off from an airport. So, if SpaceX strives for airline-type operations, why should it broadcast every launch?  

Liftoff of the Starlink 6-17 mission. Image credit: SpaceX


  1. First they make 'em returnable to Earth, then they make 'em eminently reliable, and they just keep using them. 90 launches this, that just staggers me. I thought we'd be here by about 1975 or so....!

  2. Perhaps the most significant limiting factor on reuse of these boosters is the cycle life capacity of the two propellant tanks which make up the majority of the booster mass and volume. Note: You can not change out the propellant tanks without basically creating a new booster. (Analytical cycle life determination has to do with Manson-Halford fatigue curves for the material used in the tank and other such magic.) Cycle life qualification of the tank design requires a dedicated test tank be subjected to (and survive) a minimum of 50 pressure cycles to the expected operational pressure. If the minimum of 50 pressure cycles is used for this qual test a flight tank (of the same design) can be used for one fourth of the 50 cycles, or 12 missions. (The math says 1/4 of 50 = 12.5 missions but good luck trying to fly a 1/2 mission.) If you have a tank that needs to perform 50 missions then you simply have to demonstrate that your qual tank can survive 4 x 50 = 200 cycles. (This was a real world experience for me because I actually had to do this for a tank I designed.) So, with Booster B1058 having now flown 17 missions this indicates that at a minimum its' qualification propellant tank(s) were tested for at least 68 cycles. SpaceX engineers think it can go 20 missions - which leads one to believe they've tested these tanks to over 80 cycles.

    1. Does the cycle life test include the number of times they do a short static firing on a booster? They don't fill the tanks, they just put in enough for the static firing - that is, some amount more than they burn but not much more.

      Those tests are so routine they aren't mentioned often, but I believe they do one for every mission, so 20 missions means 40 cycles. 160 cycles tested?

    2. Yes, if they pressurize the tanks to the flight operational pressure then that would be considered a cycle which should be counted. We’d actually throw in a few proof cycles during our cycle qual testing on a tank just because there would be cases when we would have to redo a proof test on a flight tank because of leaks or test equipment problems. If that situation occurred we would then have data supporting our position that the flight tank is OK to use. Note - a proof test is the initial pressure test done on every pressure vessel and is usually at 1.25X (or greater) flight pressure.

  3. I wonder how many flights they'll actually get out of one before they either stop or it fails. Crazy.

    Now if only the enviroweenies would let Starship fly!