Unlike several contemporary films where CGI is used to depict the spacecraft and the vast space, director James Gray decided to use practical effects like models and props for the spacecraft exterior shots. Also, instead of using CGI for planets, he decided to use still images to portray the surface of the planets. This same technique was used in 2001: Odissea nello spazio (1968).
Director James Gray admitted to Empire magazine that he had to compromise with the studio on the ending of the movie to get the film green-lit and even with a major star/producer like Brad Pitt on board they still struggled for years to get it made.
The production team behind Ad Astra contacted Richard Branson's Virgin group a couple of years ago and asked if they could use their branding in the movie. The company representative agreed - "We thought it was a really fun concept and were really happy to get involved." So, McBride catches a ride on a Virgin Atlantic shuttle to the moon.
The title means "to the stars" in Latin. It is often used as a shorthand for "Per Aspera Ad Astra" (Through adversity to the stars); less often for "Per Ardua Ad Astra (same meaning), which is the motto of the Royal Air Force. This phrase lingers from the sentence ("Humanity looks *to the stars* for intelligent life and the promise of progress.") just before film's title (emphasis added) appears.
At the 19:25 mark Tommy Lee Jones can be seen wearing the exact same space outfit as he did in Space Cowboys (2000). The only difference is the top two patches have been digitally altered to fit the Space Comm suits in Ad Astra.