I didn’t get much sleep last night. I, of course, stayed awake to watch the launch of the Parker Solar Probe. Sadly, that launch didn’t happen this morning as planned.
The original launch time of 3:33AM Eastern was pushed back by 20 minutes to accommodate some issues experienced in the countdown. Those issues were resolved, and a new launch time was planned for 3:53 AM Eastern time.
Then, during the polling for go-no go status, a standard check to ensure that the rocket is as ready as possible for its flight, there was a delay in some data coming from the vehicle to mission control. This resulted in a no-go and a reset.
The issue was studied, found to be something that could be worked past, and a new launch time of 4:28 AM Eastern time was set.
Polling was good, everything was a go, and then at 1 minute 54 seconds to launch something slightly scary happened. Liquid Oxygen vapor vented out from the 3 Common Core Boosters of the Delta IV Heavy, and “HOLD HOLD HOLD” was heard over the audio loop. This was so late in the countdown that the launch window was lost, and as things stand now they are preparing for another launch Sunday morning at around the same time as was planned for today.
From what I heard on the loop, it seems the issue was related to a “GH Helium Regulator.” I’m going to take an educated guess that the issue involved something in the flight pressurization systems, as helium gas is used to pressurize the tanks for better propellant feed during flight.
Sadly I don’t have details at the moment, but below is video of the event, cued to just a moment before the scrub.
UPDATE: See the bottom of this article for some basic details regarding the scrub on Saturday morning.
Delta IV is a temperamental rocket system. It seems to only want to launch when it feels like it, and while it often does have scrub situations like this, when it does launch it does so flawlessly. These are the kinds of issues you have in this field though, especially with the more complex nature of rockets which use Liquid Hydrogen as fuel.
https://en.wikipedia.org/wiki/Delta_IV_Heavy
UPDATE:
I should have stayed paying attention to the stream longer – later on in the night it was explained that the issue indeed was with the helium pressurization system on the booster. Video below shows discussion of this issue following the scrub Saturday morning.
At the time of this update, Parker Solar Probe is about 45 minutes from its next planned launch attempt, which I will of course be following.