At the end of the first orbital test flight for its 164-foot Starship, SpaceX envisions a reentry into the atmosphere at speeds approaching Mach 25, or 19,000 miles per hour, followed by 15 minutes of hypersonic flight.
During this time, the spacecraft will hurtle sideways, generating tremendous heat before adjusting to an upright position for a “soft” rocket-powered ocean landing 62 miles north of Kauai.
It will sink in the Navy’s Pacific Missile Range Facility, according to plans for the historic flight, and join dozens of warships that have gone down over past decades during Navy “sink exercises” in waters 15,000 feet deep.
Most recently that included the retired frigate USS Ingraham, which was targeted in mid-August by Marines firing Naval Strike Missiles from Kauai and pummeled by munitions from aircraft and a submarine.
Hawaii’s role in the orbital test of the biggest rocket ship ever built — 394 feet with the “Super Heavy” booster and Starship upper stage combined — has largely been revealed through regulatory filings.
Eventually, Starship is expected to carry crews to Earth orbit, the moon and Mars.
NASA, for its part, wants to fly a WB-57 high- altitude research jet close enough to the 30-foot-wide Starship’s hypersonic reentry to gauge the surface temperature of the “Starbrick” thermal tiles that will take the brunt of the heat. Controllable fins will keep Starship in the right position.
Current state-of-the-art thermal protection systems, or TPS, including ablators, ceramic tiles and reinforced carbon fiber “typically require significant maintenance between flights,” meaning inspection, replacement time and cost, an Aug. 24 NASA report stated.
“Starship TPS is intended to provide a dramatic leap forward by demonstrating operational reuse requiring minimal to no maintenance between flights,” NASA said.
The space agency also offers a possible window for the Starship launch, saying it is “targeting (a) Starship reentry observation opportunity near March 2022.”
The timing is perhaps a more realistic estimation compared to a series of overly optimistic predictions by SpaceX founder Elon Musk, who tweeted on Oct. 22: “If all goes well, Starship will be ready for its first orbital launch next month, pending regulatory approval.”
Musk needs approval from the Federal Aviation Administration, and an environmental assessment is ongoing. The first orbital mission would include the stacked rocket launching from the SpaceX Boca Chica “Starbase” in Cameron County, Texas, with the Super Heavy booster first stage landing in the Gulf of Mexico and Starship second stage splashing down off Kauai after traveling nearly around the Earth in orbit.
Super Heavy is expected to be equipped with up to 37 “Raptor” engines powered by liquid oxygen and liquid methane, according to the draft programmatic environmental assessment released in September. Starship will employ up to six Raptor engines.
The flight is expected to take 90 minutes. As Starship enters its landing approach, likened to a speed-reducing belly flop, a sonic boom will be created.
“It is SpaceX’s intent to recover and reuse Starship and Super Heavy boosters,” a June FAA biological assessment states. But the space company may require “expending” either in the ocean “during early launches as the program develops.”
Its first proposed mission includes “the Starship second stage landing off the coast of Hawaii in the Pacific Ocean,” the FAA said in an Oct. 18 document.
“SpaceX expects Super Heavy and Starship would break up on impact” and sink because the spacecraft are mostly made from steel, a separate FAA report said.
Musk’s space flight operation has not identified all potential options for future landing sites and “may plan to land the Starship on islands in the Pacific Ocean,” which would be analyzed in future reports if plans develop, according to the environmental assessment.
Ted Ralston, a retired aerospace engineer, said Hawaii would likely be ruled out for a land-based return. Rather, SpaceX may have in mind sparsely populated or uninhabited islands in the Western Pacific with little commercial air traffic, he said.
Eventually, SpaceX wants to launch and land its Super Heavy boosters and Starships back at Boca Chica — and it is adding steel arms at its 450-foot “Mechazilla” launch tower to “catch” the returning vehicles.
“Getting the permits to do the landings in Texas of the type that they are thinking of doing, which is a ballistic reentry, might be more complicated than getting that kind of permission in a more inviting atmosphere in the Western Pacific,” Ralston said. “And then you get the thing developed under say, three or four flights — now you’ve proven it. Now you can move it back to Texas. So you kind of look for the path of least resistance and develop and establish capability and credibility, and with that you can back your claim that you are OK to go back to the FAA.”
It would be relatively easy to barge the landed Starships from a Pacific island back to Texas, he said.
PMRF is the world’s largest instrumented range capable of supporting surface, subsurface and space operations. The Navy said the facility has over 1,100 square miles of instrumented underwater range and over 42,000 square miles of controlled airspace.
In August, U.S. Indo- Pacific Command said PMRF was “in discussions (with SpaceX) for limited support and use of their range” for the ocean touchdown.
