Per ardua ad astra ("Through adversity to the Stars") is the motto of the Royal Air Force and other Commonwealth air forces such as the RAAF, RNZAF, and the former RCAF. It dates from 1912 and was used by the newly-formed Royal Flying Corps.
Not long after this, two junior officers were walking from the Officers' Mess at Farnborough to Cody's Shed on Laffan Plain. As they walked they discussed the problem of the motto and one of them, named J. S. Yule, mentioned the phrase "Sic itur ad Astra", from the Virgilian texts. He then expanded on this with the phrase "Per Ardua ad Astra", which he translated as, "Through adversity to the Stars". Colonel Sykes approved of this as the motto and forwarded it to the War Office. It was then submitted to the King, who approved its adoption.
The question of where this motto had come from can be answered by the fact that Yule had read it in a book called The People of the Mist by Sir Henry Rider Haggard. In the first chapter was the passage, "To his right were two stately gates of iron fantastically wrought, supported by stone pillars on whose summit stood griffins of black marble embracing coats of arms and banners inscribed with the device 'Per Ardua ad Astra'".
As to where Rider Haggard obtained this phrase is still unclear although it is possible that it originated from the Irish family of Mulvany who had used it as their family motto for hundreds of years and translated it as "Through Struggles to the Stars".
The authoritative translation of the motto is just as unsure as the source. Since there can be a number of different meanings to "Ardua" and "Astra"", scholars have declared it to be untranslatable. To the Royal Air Force and the other Commonwealth air forces, however, it will remain translated as "Through Struggles to the Stars".
St Chad's College, Durham annually awards a Per ardua ad astra scholarship.
Per ardua ad astra is also used as the motto for the Welsh Space Programme (in which monkeys that knew sign language were sent into space) in the Malcolm Pryce novels about Aberystwyth.
In the Buck Rogers television series, the motto is displayed on the side of Buck Roger's spaceship The Searcher.