There are plenty of reasons to get excited about Tuesday's (May 19) planned test flight of SpaceX's Starship megarocket.
For starters, it will be the first launch of Starship — the biggest and most powerful rocket ever built — in nearly seven months. And, while the mission will be Starship's 12th overall, it will mark the debut of the advanced new V3 vehicle, which features a number of important modifications and upgrades compared to its predecessors. (That helps explain the long launch lacuna.)
Finally, while Starship will fly a familiar suborbital trajectory on Flight 12, it will do something completely new while it's up there — take a good, long look at itself.
The Flight 12 plan calls for Starship's upper stage, known as Ship, to deploy 22 dummy versions of SpaceX's Starlink broadband spacecraft. These will be "similar in size to next-generation Starlink satellites," SpaceX wrote in a Flight 12 mission description.
That's an important detail: SpaceX has said that one of Starship's main tasks when it comes online will be to finish building out the Starlink megaconstellation. (Other key jobs will be ferrying astronauts to the lunar surface for NASA's Artemis program and helping set up a colony on Mars.)
That number marks a considerable increase over previous Starlink flights, during which Ship has carried eight or 10 such mass simulators. And there's another important difference as well — the Flight 12 dummy-Starlink batch includes two inspector spacecraft.
"The last two satellites deployed will scan Starship's heat shield and transmit imagery down to operators to test methods of analyzing Starship's heat shield readiness for return to launch site on future missions," SpaceX wrote in the mission description. "Several tiles on Starship have been painted white to simulate missing tiles and serve as imaging targets in the test."
This focus on the heat shield should not come as much of a surprise. After all, protecting returning spacecraft from the intense heat and other rigors of atmospheric reentry is a tough task, as we learned in the leadup to NASA's Artemis 2 moon mission with all the discussion about the Orion capsule's heat shield.
And protecting Starship is far harder, given that the vehicle is designed to be fully and rapidly reusable. Each Orion capsule's heat shield has to do its job just once, but each Ship vehicle will eventually launch and return to Earth multiple times per day, if all goes according to plan.
Indeed, SpaceX founder and CEO Elon Musk has flagged Ship's heat shield, which consists of about 40,000 hexagonal tiles, as the biggest hurdle facing the vehicle at the moment.
"The single biggest remaining problem for Starship? It's having the heat shield be reusable," Musk said in February on the Dwarkesh Podcast.
"No one has ever made a reusable orbital heat shield," he added. "So, the heat shield's got to make it through the ascent phase without shucking a bunch of tiles, and then it's got to come back in and also not lose a bunch of tiles or overheat the main airframe."
Ship's heat shield has done its job before; the vehicle has survived the journey back to Earth and splashed down softly in the ocean on multiple previous test flights. But improvement will be needed to get Starship where SpaceX wants it to go, according to Musk.
Ship lost a lot of tiles during on those previous flights, so "it was not reusable without a lot of work," the world's richest person said on the podcast. "If you want to be able to land it, refill propellant and fly again, you can't do this laborious inspection of 40,000 tiles type of thing."
If all goes to plan on Tuesday, Starship's first stage, a giant booster called Super Heavy, will steer itself to a controlled splashdown in the Gulf of Mexico about seven minutes after liftoff. (There will be no dramatic catch of the booster by the launch tower's "chopstick" arms, as we've seen on several previous flights.)
Ship, meanwhile, will splash down in the Indian Ocean about 65 minutes after launch, as it has done multiple times before. But we should get some new, in-space views of the heat shield before that, giving us some clues in real time about how the harrowing reentry may go.
