In the Blue Origin YouTube video Replay of New Shepard Mission 8 Livestream, the first of several hold starts at T- 03:00 when the video is at about 16:27, but T = 00:00 and ignition do not come until more than 22 minutes later at about 38:51 in the video.

Since there is no human payload and the target altitude may be less than that planned for commercial missions, significant boil-off of the cryogenic LH2 and LOX propellants might be tolerable.

I have no idea how the boil-off rate might compare to other launch systems; this part of West Texas is arid desert (today's humidity will be 15% for example), so the cold boil-off vapors would not produce as much visible steam as it would in Florida.

Will the New Shepard be able to have the crew board after fueling and also tolerate substantial launch holds without the crew exiting or refueling or top-offs?

Video is queued just before the beginning of the first hold.

Blue Origin Launch Site West Texas

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    $\begingroup$ I'm pretty sure in actual human launches they'll never hold the countdown, they're just testing right now $\endgroup$ – Dragongeek Apr 30 '18 at 15:28
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    $\begingroup$ For what it's worth, shuttle launches had holds with crew onboard all the time. I expect for New Shepard it will be a combination of technical requirements (boil-off as you mentioned) vs. business requirements (must get to space altitude) vs. human requirements (how long can you sit on your back). Your question did remind me of the unfortunate hold conditions for New Shepard's namesake during the first Mercury launch. $\endgroup$ – Carlos N May 7 '18 at 19:34

LOX and LH2 tanks that are boiling from equilibrium can be replenished via umbilicals. You can see one here:

enter image description here

In some launch videos, it can be seen to detach right around engine start time. This lets any boil-off be replenished right up to launch.

Note this is different from the Falcon 9, where the issue isn’t boil-off but rather warming of the deeply-cooled LOX. As the F9 LOX warms it expands; the F9 no way to recool it in place (though it might be possible), which limits how long the launch can hold.

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  • $\begingroup$ Ah, there are some (at least one) advantage to boiling-point (non sub-cooled) propellants. $\endgroup$ – uhoh May 28 '18 at 3:10
  • $\begingroup$ I'm not sure "...there’s no way to recool it in place..." is true, I think there's an answer to another one of my questions that explains how this is done, I'll take a look. $\endgroup$ – uhoh May 28 '18 at 3:10
  • $\begingroup$ Found it! See this excellent answer to the question Why would sub-cooled LOX tanks need to “topped-off” until the last minute or so? $\endgroup$ – uhoh May 28 '18 at 5:05
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    $\begingroup$ @uhoh Thanks! Have clarified and added a link. Also, it looks like your previous question didn't really get an answer about topping off, will look into that. $\endgroup$ – Bob Jacobsen May 28 '18 at 17:15
  • $\begingroup$ If there is continuos ice build up on the tanks for LOX and LH2 during a hold of countdown, the ice layer may get too thick and heavy if hold is extended too long. $\endgroup$ – Uwe May 28 '18 at 19:48

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