Image Source: Mary @BocaChicaGal/ NASASpaceflight
Japanese entrepreneur Yusaku Maezawa booked a space voyage around the moon with SpaceX, he has been funding the development of the company's next generation spaceship-rocket duo. The target launch date of the moon trip is the year 2023. Starship will be a 50 meter tall vehicle with the ability to carry up to 100 passengers. Starship will require a gigantic Super Heavy rocket booster, to get out of Earth's atmosphere. Both, Starship and Super Heavy together will be 118 meters tall!
Super Heavy will utilize the similar technology seen in SpaceX's Falcon 9 rocket, it will have the ability to get Starship out of our planet and return from space to land vertically on a spaceport, in order to be reused. The founder of SpaceX, Elon Musk, said both of these vehicles will be fully and rapidly reusable, which in turn reduces the cost of spaceflight enough to make Moon voyages and building the first colony on Mars economically feasible.
The first prototypes of Starship are under development at their SpaceX South Texas facility located in the city of Brownsville's Boca Chica Beach. Since the last week of December, teams have been working quick to build the crafts inner structure, they are currently working on the first flight version design of Starship called SN1. "We’re now building flight design of Starship SN1, but each SN will have at least minor improvements, at least through SN20 or so of Starship V1.0." Musk shared.
We’re now building flight design of Starship SN1, but each SN will have at least minor improvements, at least through SN20 or so of Starship V1.0.— Buff Mage (@elonmusk) December 28, 2019
SpaceX teams have finished constructing 3 stainless-steel dome tanks, also known as bulk heads, that make up the inner structure of the craft. These domes will keep Starship SN1 stable enough to hold internal hardware, withstand highly pressurized propellant tanks, and make the craft strong enough to endure extreme forces during flight. It is the most difficult part of the craft to build because they must make the bulk heads light enough to not add too much weight to the craft, but strong enough to endure heavy gravity forces during launches, also the fury of a fiery orbital reentry.
SpaceX conducted a test on one of the dome tanks earlier today, to check how much pressure the steel structure and welding technique could withstand. During the test they intentionally pressurized the bulk head dome until it exploded. This planned pressurize-until-explosion test was preformed to ensure the assembly of all the welds and design structure of the tanks are strong enough for Starship SN1 flight design. Musk shared some details about the test results:
"Dome to barrel weld made it to 7.1 bar, which is pretty good as ~6 bar is needed for orbital flight. With more precise parts & better welding conditions, we should reach ~8.5 bar, which is the 1.4 factor of safety needed for crewed flight."
Today's tank dome pressurization gave the engineers a positive result. Musk further explained that "A given tank pressure is needed to feed the engine turbopumps & pressure-stabilize/relieve compression load on the cylinder walls. Everything is compressible, but liquid compression at these pressures is not significant. However, the tanks do expand under pressure, creating a bit more volume. Keeping propellant super cold has a big effect on density of ~10% in case of CH4 (methane)."
Everything is compressible, but liquid compression at these pressures is not significant. However, the tanks do expand under pressure, creating a bit more volume. Keeping propellant super cold has a big effect on density of ~10% in case of CH4.— Buff Mage (@elonmusk) January 10, 2020
Previously, he said that the welding can be affected by Boca Chica's windy weather, so to make sure the welding of Starship is stronger they will build the next vehicles in an enclosed environment. Down the road at Boca Chica several structures can be seen under construction already.
"Moving to an enclosed (fairly) clean room environment for SN2 in Jan, although, unlike aluminum, stainless steel welding is not super sensitive. Our main issue here in Boca is that it can get very windy, which affects weld arc & steel melt pool."
SpaceX will continue to test dome tanks in the coming weeks, then build a better version of the domes, to later stack Starship with a sturdy inner structure. Starship SN1 will conduct high-altitude flights above Boca Chica in approximately 2 or 3 months. They also aim to conduct an orbital flight soon. Company representatives have shared that the first operational Starship flights, that will likely deploy into orbit commercial communications satellites, could take place as early as 2021.