SpaceX has been very busy developing its Starship prototypes lately. Given recent activity at the Boca Chica facility and recent imagery Musk himself provided, they seem poised to make their biggest leap yet. Yesterday, October 14th, Musk announced that the eighth prototype of the spaceship (SN8) had received the three Raptor engines it will use to travel its planned 15.25 km (50,000 ft).
The addition of the three Raptor engines came after the SN8 underwent three rounds of cryogenic proof testing last week. The first was a success according to the test parameters, but as Musk indicated on Twitter, a small leak opened "near the engine bearings, which is possible due to the differential shrinkage". After repairs, a second and third round took place over the next few days.
Similarly, the company tested its SN7.1 test tank for errors on the evening of September 23, which came after two successful hop tests on the prototypes SN5 and SN6 – both flew at 150 m (~ 500 ft) and landed safely. Three Raptor engines (SN 39 models) were installed on Sunday after the thrusters were removed from under the hull of the SN8.
With these motors now integrated, it is clear that SpaceX is preparing for the first static fire test in which multiple motors are started at the same time. In preparation for this, the ground teams will use the SN8 to conduct an extensive series of tests consisting of refueling tests, a spin prime test and pre-burner tests.
After the static fire test is complete, the ground team reviews the data to determine the performance of the engines and associated systems. This is followed by the integration of the nose cone, to which its aerodynamic surfaces (its front fins or canards) are currently attached – similar to how the fuselage has received the two large flags on its sides.
Live streaming footage from NASA Spaceflight's Mary McConnaughey (aka @BocaChicaGal) showed the spacecraft's nose cone getting its fins and then moving it into the facility's windbreak (video below). Once the entire hull is stacked and combined, a second static fire test is expected – only this time the propellant is stored in the collection tank in the bow cone.
If everything goes according to plan, the SN8 will attempt the highest hop test yet. So far, a prototype has reached its highest altitude of 150 m (~ 500 ft), which was first reached by the Starship Hopper, followed by the SN5 and SN6. The ~ 15.25 km long hop test also includes a "bellyflop" maneuver, during which the aerodynamic surfaces of the spaceship are tested.
This maneuver begins as soon as the SN8 has reached its highest altitude and begins to descend. At this point the ground team will turn off the engines and tilt the prototype's hull towards the ground. The SN8 then relies on its maneuvering fins to control its descent, and its engines are re-ignited at the last second for safe up and down landing.
Meanwhile, the SN9 prototype is currently in Mid Bay in Boca Chica while preparations are underway for stacking the SN10 in the opposite bay. The SN11 is also preparing for batch operations, and sections of the facility that are expected to be used to manufacture the SN12, SN13 and SN14 prototypes have been seen (video below).
Back in August, Musk had tweeted that the newer SN40 Raptor engine was being tested at the company's test facility in McGregor, Texas. In addition, work on the High Bay facility where the Super Heavy is stacked is almost complete. Parts of it have also been seen in the Boca Chica area. This is all in line with SpaceX's policy of rapid prototyping and testing to failure, which requires backup prototypes to be in place.
It remains unclear when this altitude hop test will take place, but Musk has indicated several times over the past month that it will take place soon. Musk has also said he hopes to orbital flight one of his prototypes next year. This will be the last hurdle before commercial areas can be started with the vehicle.
Further reading: Teslarati, NASA SpaceFlight