I author this question off of two failed cross-country trips to see NROL-44 and three lost bets on whether it'll launch. As ULA scrubs this Delta IV Heavy yet once again, I wonder, has there ever been any other rocket so delayed?

I understand that the vehicle to carry NROL-44 has been stacked for a very long time awaiting a late payload. Not only that, it's been several weeks since the scrub-after-ignition during the first launch attempt (which itself was postponed several times due to weather).

I suppose answers can offer both "longest complete rocket awaiting launch" and "longest delay between first launch attempt and actual launch". Maybe throw "most scrubs" in there, if so inclined.

Note: answers do not have to be the longest delayed rocket, runners-up are fantastic too. We celebrate space history here, even the painful parts.

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    $\begingroup$ Feel your pain. I was pretty lucky with trips to see shuttle launches - I saw 3 of 4 I tried to see. STS-133 slipped too much and I missed it. I have some ideas on the most delayed shuttle flight, I'll look into it. $\endgroup$ Commented Oct 1, 2020 at 14:04
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    $\begingroup$ For some values of "mission" likely quite relevant to the subjects, Deke Slayton? John Glenn flight #2? $\endgroup$ Commented Oct 1, 2020 at 19:02
  • $\begingroup$ Probably we should be more specific about "complete rocket awaiting launch". At what moment exactly a rocket is "complete"? Probably when Flight Readiness Review (or analog) is completed. Rocket's hardware can be ready long before that, months or even years. $\endgroup$
    – Heopps
    Commented Oct 2, 2020 at 8:32
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    $\begingroup$ @user3528438 NOAA-19? Well, it's a payload, not a rocket... but still, please write an answer up about that! Some of these delays are insane & I love to learn more about each story. $\endgroup$ Commented Oct 3, 2020 at 21:34
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    $\begingroup$ The most famous delayed mission was the first crewed mission ever from the US: Mercury-Redstone 3 with Pilot Alan Shepard. The delays/postponements/scrubs lead to a total delay of 3 days and a wetted spacesuit. $\endgroup$ Commented Oct 3, 2020 at 22:02

3 Answers 3


At least 497 days, 16 months.

NASA's ICON mission was fully stacked some time prior to June 6 2018 when the carrier aircraft took off on a ferry flight to its then planned launch site at Kwajalein Atoll only to turn around mid-flight after problems were detected in the rocket. Previous problems had already delayed it by over a year, but it's not clear when during that period it was first stacked. After additional problems with the Pegasus XL rocket it finally flew on October 11, 2019.

  • $\begingroup$ Had the vehicle been assembled for the 2017 launch? if so, wow. Didn't sound like it from this, though. "The satellite, also built by Orbital ATK, was placed in its shipping container at the contractor’s Gilbert, Arizona, assembly facility last month to await clearance to head to Vandenberg, he said." That was in Nov 2017. spaceflightnow.com/2017/11/10/… $\endgroup$ Commented Oct 3, 2020 at 19:43
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    $\begingroup$ The multi-year trainwreck that Icon's launch turned into presumably played a large part in Nasa and SpaceX contracting depts figuring out a way to sell a Falcon 9 for 50 million dollars (later reduced to a bit over 40m ) without jeopardizing SpaceX's ability to sell normal launches at full cost for the IXPE mission which was originally designed for a Pegasus launch to low equatorial orbit. $\endgroup$ Commented Oct 3, 2020 at 20:21
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    $\begingroup$ I took "longest complete rocket awaiting launch" to mean it had to be stacked. If delays in planned launch dates are on the table - the shuttle flights after the failures would be multi-years. $\endgroup$ Commented Oct 3, 2020 at 20:30
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    $\begingroup$ @OrganicMarble agreed. Revised accordingly. $\endgroup$ Commented Oct 3, 2020 at 21:52
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    $\begingroup$ 16 months, still wow! $\endgroup$ Commented Oct 3, 2020 at 23:06

For shuttle at least, I believe the longest delay was the torturous launch flow of STS-35. (tl;dr it was delayed six months.)

Using the criteria in the Space Shuttle Missions Summary, namely

  • Postponements are defined as launch delays which occurred prior to call-to-stations for OMI S0007 Shuttle Countdown.

  • Scrubs are launch date changes after the start of Shuttle countdown (countdown was terminated or recycled to a later launch date).

  • Delays are delays which occur only on the day-of-launch.

So this is about delays & scrubs that happened after the vehicle was stacked and rolled out to the pad, not about postponements, i.e. changes in the planned launch date before the vehicle was stacked.

The first official launch date for STS-35 was May 30, 1990. During tanking on that day, hydrogen leaks were detected at the orbiter / external tank (ET) interface. After a tanking test on June 6, a pad repair was deemed undoable so the stack was rolled back to the Vehicle Assembly Building (VAB) on June 13. Columbia was removed from the stack and moved back to the Orbiter Processing Facility. The umbilicals on both the orbiter and ET were changed out.

The orbiter was returned to the stack and it rolled back to the pad on August 9 for a September 1, 1990 launch date (94 days after the first attempt).

Issues with the payload then caused a slip to September 4, 1990 (98 days after the first attempt). During tanking on that day...hydrogen leaks were again detected. heavy sigh from everyone in the program. Work started in orbiter aft compartment to track down and fix leaks.

After aft compartment work was completed the next attempt was September 17, 1990 (110 days after the first attempt). During tanking on that day...hydrogen leaks were again detected. very heavy sigh from everyone in the program.

The STS-35 stack was then rolled to Pad B so Atlantis could launch on STS-381 as planned from Pad A. Then there was a tropical storm (Klaus) which forced the stack to be rolled back to the VAB yet again. Back to pad B on October 14, 1990. On October 30 a tanking test was conducted. No leaks!

The launch date was then set for December 2, 1990 (186 days after the first attempt). Tanking went well - no leaks - and after a brief range delay, it finally launched. sigh of relief from everyone in the program.

Additional reference: NASA STS-35 Mission Page

enter image description here

STS-35 and STS-38 passing each other to and from the VAB on the crawlerways during the "summer of leaks". Photo credit-NASA


1 The referenced NASA page is wrong about the mission that forced the pad switch (it says STS-36). I originally thought it was STS-41, which was the 36th flight, and that they were confused by the "36th flight",but even that is wrong. STS-41 (10/6/1990) and STS-38 (11/15/1990) both launched during STS-35's launch campaign, and STS-41 launched off Pad B as planned. STS-38 launched off Pad A. STS-36 had already launched in February 1990. It was a very confusing summer.

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    $\begingroup$ Lovely answer. Torturous is an apt word! $\endgroup$ Commented Oct 1, 2020 at 15:34
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    $\begingroup$ That photo is pretty darn awesome! $\endgroup$
    – Ludo
    Commented Oct 1, 2020 at 16:11
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    $\begingroup$ I was thinking if the time between STS-335 becoming STS-135 qualified for this question, but that was only 2 months... $\endgroup$
    – Ludo
    Commented Oct 1, 2020 at 16:17
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    $\begingroup$ @Ludo I would bet that the "postponements" = planned launch date changes for the 2 missions after the accidents were probably years. I remember them being "always 90 days away" which caused a lot of frustration and inefficiency. $\endgroup$ Commented Oct 1, 2020 at 16:25
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    $\begingroup$ @Ludo STS-335 changed to STS-135 in January 2011. Stacking for the mission started in March 2011 and the ET was added in April. en.wikipedia.org/wiki/STS-135 nasa.fandom.com/wiki/STS-135 I have to say though, in September 2010 we were already convinced it was going to happen and started crew training. $\endgroup$ Commented Oct 1, 2020 at 17:19

269 Days, almost 9 Months

HETE-2 was attached to its Pegasus launch vehicle in December, 1999, ready for a January launch. But then, NASA got cold feet. On January 14, 2000, they decided to postpone the launch. We had built it in an MIT lab for about 1/3 what the parametrics said it should cost, and that made some people nervous. Even though it was already well-tested, NASA demanded more testing. So, back to Massachusetts it went. No problems were discovered. We finally launched on October 9, 2000.



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