Relativity's First Terran Launch Scrubbed

Rather less surprising than yesterday's loss of the JAXA H3, this afternoon's attempt to launch Relativity Space's first Terran -1 test flight was scrubbed almost at the end of their three hour test window.  I started paying attention to the video feed around a half hour before the 1:00 PM (1800 UTC) start of the launch window, and several times during the window they'd count down to 20 minutes or so and then hold over a problem with "fuel conditioning."   

They were counting down to launch in the 2:30 time frame when the system went into a hold with 70 seconds left before launch.  Very little was said for the next 20 minutes, but earlier in the countdown, they had said that after they reached T-1:00 any abort would automatically carry out a group of changes which would require a big enough reset that the day's attempt would be scrubbed.  They held at T-1:10 until around 3:00 PM and then announced a final launch time of 3:45 PM.  Not long after they resumed counting, they went into a hold and within a few minutes cancelled for the day.  The company site Tweeted this at 3:45 PM.

The #GLHF hashtag is for the mission's name, "Good Luck Have Fun." 

The propellant conditioning explanation given for the holds all afternoon including the final scrub appear to have been associated with Stage 2.  A few hours after the above tweet, they added:

When using liquid natural gas, the methane needs time to get to the right concentration. This is why our next attempt will be a few days from now. More to come soon! 

Exactly why this was a problem today and not in other fueled tests, such as this upper stage being fired for full duration at NASA's Stennis Space Center, is the heart of what they're investigating.  I interpret what they're saying is that they have instruments that measure the liquid methane temperature and the holds were related to out of range numbers.  This could be a sensor on the vehicle, in the Ground Support Equipment, or something unrelated to sensors.

All that out of the way, Relativity might have gotten off easy with not launching today.  Remember, this launch vehicle is mostly 3D printed, 85% by mass.  Nobody has successfully launched a 3D printed rocket.  It could well be that the biggest test here is the 3D printed structure of the vehicle and engines around the time it passes through maximum dynamic pressure (Max Q).  

Plus, remember that just making orbit on a first try is a remarkable achievement.  No private company has ever launched its first independently developed, liquid-fueled rocket and had it reach orbit on the first try.  

Add in that this is a methane-oxygen fueled rocket.  Nobody has gotten one of those into orbit, either.  Starship could try this month, Vulcan says they'll try in May.  These guys may try in a few days, although they haven't announced it yet.  They could be the first. 

The Terran-1 at Launch Complex 16 on Cape Canaveral.  Relativity Space/Trevor Mahlmann photo