With the arrival of a new Raptor engine at their Boca Chica launch facility, SpaceX is gearing up for a second round of testing with the Starhopper vehicle in South Texas. The latest test campaign is slated to begin in mid-June and is expected to include the first untethered hop of Starhopper. Meanwhile, on the Florida side, SpaceX continues to make progress with their plans to utilize Pad 39A for the Starship program.
The Starhopper vehicle is a testbed for the development of SpaceX’s upcoming Starship spacecraft. The launch provider hopes to one day utilize the fully reusable Starship system to launch humans and cargo to the Moon and Mars.
Starhopper performed its first two hot-fire tests at the beginning of April. During the tests, a single Raptor engine was fired for a couple of seconds to verify that Starhopper was ready for more rigorous testing including untethered hops to higher altitudes.
Following the April events, the Raptor engine – designated SN2 – was trucked away for post-testing analysis. Then, work quickly began to prepare the Starhopper vehicle for the next phase of testing.
This work included the installation of quick disconnect umbilicals, attitude control systems, and shock absorbers on the legs of the Starhopper.
These systems will allow Starhopper to perform untethered hops from SpaceX’s launch facility in Boca Chica, Texas.
The first untethered hop is currently scheduled for mid-June – with the Starhopper expected to target an altitude of around 20 meters. However, prior to the hop, SpaceX is also set to perform fueling, ignitor, and preburner testing along with a static fire of the Raptor engine.
That being said, it should also be noted that the test plans for the Starhopper vehicle are rapidly evolving, so the events are heavily subject to change.
For instance, up until recently, the company was planning to utilize Raptor SN4 for the untethered hops. However, the company has now decided to utilize this engine only for fit checks, and will instead perform the hops with SN5 – the latest Raptor to come out of SpaceX’s factory in Hawthorne, California.
SN4 arrived in Boca Chica for the fit checks on Friday afternoon. Meanwhile, SN5 is already at SpaceX’s test facility in McGregor Texas for verification testing before being shipped south.
While the precise reason for the engine change is unknown, by still shipping SN4 to Boca Chica first, SpaceX will be able to ensure that the Starhopper is ready for hopping ahead of SN5’s arrival. This should help to reduce the delays caused by waiting for SN5.
Once SN5 arrives, SpaceX is expected to quickly dive into the test campaign. However, as seen with the previous round of hot fire testing at Boca Chica, it may take several attempts to conduct each of the various tests.
Raptor is a full flow staged combustion cycle engine running on methane. An engine of that class has never been used to launch a vehicle into space. Therefore, its development is heavily subject to growing pains. Furthermore, the methane ground support systems are also new to SpaceX, as their currently operational vehicles use RP-1 for propellant.
Subsequently, it is anticipated that the teams will encounter issues during the testing in Boca Chica.
The lessons learned from the Starhopper vehicle will be used to influence the design of the more advanced Starship prototypes. The vehicles are currently being built simultaneously in both Boca Chica Texas and Cocoa Florida.
It is understood that the Texas-based vehicle has been designated Mk.1 while the Florida-based vehicle has been designated Mk.2.
The Texas and Florida-based teams are competing to see which is most effective at building and launching the spacecraft.
While the Mk.1 prototype has had SpaceX’s launch site in Boca Chica lined up for its test flights, the launch site for the Mk.2 vehicle had been slightly more uncertain.
SpaceX already has two launch pads in Florida, but both are being actively used to support the Falcon 9 and Falcon Heavy rockets. Therefore, the company had been looking at a variety of options for launching Starship.
However, Pad 39A has recently become the frontrunner to support Starship. While it is perhaps the obvious choice when considering its large size, the launch complex is also needed to support critically important Falcon launches.
These include national security missions for the U.S. Air Force on Falcon Heavy and Crew Dragon launches for NASA’s Commercial Crew program on Falcon 9.
NASA and the Air Force are SpaceX’s largest customers, and thus it is vitally important that the Starship testing does not pose a significant risk to the launch provider’s ability to support its existing manifest.
The good news is that Air Force and NASA missions will likely only be launching from Pad 39A a couple of times a year, and thus there will be plenty of downtime for the Starship testing.
Therefore, as NASASpaceflight.com reported last month, SpaceX is exploring the addition of a second launch mount to the east of the existing Falcon infrastructure.
Since then, more details about the proposal have emerged including plans for a landing zone.
Due to Starship’s large diameter of approximately nine meters, transporting it will be difficult. Consequently, SpaceX wants to land the vehicle following launches at a proposed landing pad inside the fence of Launch Complex 39A.
Specifically, current plans call for the landing zone being placed on the east side of the pad between the Horizontal Integration Facility and the Falcon launch pad.
While the plans for both the launch and landing complexes are still in the early design phase and are subject to permitting and environmental reviews – several sources have confirmed that these plans are under serious consideration.
Interestingly, it is also understood that the potential modifications to Pad 39A may include the ability to support Super Heavy – not just Starship test flights.
Super Heavy is the first stage booster which will be used to launch Starship into orbit. The rocket will fly with 31 engines on fully operational flights, but SpaceX CEO Elon Musk has stated that it will likely fly with around 20 to reduce the risk during the early test flights.
That being said, even with 20 Raptor engines on Super Heavy, it will still generate a similar amount of thrust as the Saturn V. Therefore, it is unclear if SpaceX would still use a secondary launch mount for Super Heavy.
Utilizing the primary launch mount at Pad 39A would seem to be preferable given Super Heavy’s power. In fact, the Saturn V has already flown from that exact spot.
However, it is also possible that doing so may not be possible, as it would pose too much interference to the Falcon program.
Musk is expected to provide an update on the Starship program later this summer which may help to shed more light on SpaceX’s plans for the launch complex.
Additionally, further tweaks to the design of the Starship and Super Heavy vehicles are expected at the presentation. However, the changes are anticipated to be far less drastic compared to the ones announced at previous Starship update presentations.