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Space is hard. That's a refrain we keep hearing. It applies to Boeing's uncrewed Starliner mission, which launched Friday morning, but won't make it to the International Space Station as planned.

SpaceX founder Elon Musk knows how challenging it is to escape Earth. He tweeted a message of encouragement to NASA and Boeing on Friday. "Orbit is hard. Best wishes for landing and swift recovery to next mission," Musk wrote.

Orbit is hard. Best wishes for landing & swift recovery to next mission. — Elon Musk (@elonmusk) December 20, 2019

Both SpaceX and Boeing are part of NASA's Commercial Crew Program, which aims to bring astronaut launches back to US soil for the first time since the end of the space shuttle era in 2011.

SpaceX already successfully sent an uncrewed Crew Dragon capsule to the ISS earlier this year. Boeing was hoping to match SpaceX's achievement, but a glitch caused Starliner to use up too much fuel. Instead of meeting up with the ISS, Starliner will attempt to come back to Earth early.

It's unknown how Starliner's troubles might impact Boeing and NASA's plans for sending humans to the ISS. SpaceX is currently putting its Crew Dragon systems through safety testing with an eye on an astronaut launch in early 2020.

SpaceX may be ahead in the race, but Musk's tweet feels like a genuine message of support.