(CNN) A new problem throws four astronauts’ impending moon journey into uncertainty. Quoting,

Because hydrogen is the lightest element in the universe, it tends to leak out of anything intended to contain it. And after hydrogen seepage plagued the first wet dress rehearsal for Artemis II in early February, the space agency worked to replace two seals around the rocket’s propellant lines in an attempt to better confine the fuel.

This requires some context. All  particles in the universe are either fermions or bosons. Fermions have characteristics of ordinary matter familiar to us. One of these is that two particles of matter can’t be in the same place at the same time. On the other hand, bosons, like the photons that comprise light, have no problem.  Cross the beams of two flashlights, and the beams pass through each other  without colliding.

Hydrogen is the lightest element, but helium is the smallest. Hydrogen has a single electron, which has spin 1/2 or -1/2, which makes hydrogen behave as an obvious fermion. Fermions cannot occupy the same space, which results in an effective “size”. The two paired electrons of helium, have opposite spins, cancelling: 1/2 – 1/2 = 0. This makes helium atoms behave like quasi-bosons, which can be closer together than hydrogen can tolerate, until electrostatic repulsion takes over.

So helium is much “smaller” than hydrogen. Famously, it can pass through the glass of old-fashioned vacuum tubes, ruining them.

The inability to solve these leaks probably stems from multiple attempts to substitute for the extremely high costs of techniques used during the Apollo project almost 60 years ago. It is symptomatic of the thinking that also replaced a known-good heat shield technology with something extremely dangerous. See (CNN) NASA is about to send people to the moon — in a spacecraft not everyone thinks is safe to fly; the Stockton Rush Syndrome.

Since the engineers seem to have forgotten the basic Bayesian statistics that govern how many will live and how many will die, perhaps a rare appeal to the politicians is in order. This is going to look extremely bad for you,.