First noticed by NASASpaceflight.com forum member “exilon”, SpaceX appears to have selected off-the-shelf Tesla battery packs as the power storage method of choice for its Starship Mk1 prototype, currently in the midst of a busy period of integration
Potentially taken directly from Tesla Model S/X powertrains otherwise headed for recycling, SpaceX technicians have spent the last 24 or so hours attaching numerous battery packs to part of a Starship subsystem known as header tanks. This is the latest addition to SpaceX and Tesla’s relatively close relationship – the two have begun to work together to solve challenges with materials science, batteries, and more within the last 12-24 months.
While initially surprising, the appearance of battery packs quite literally taken from Tesla Model S/X vehicles or their Gigafactory assembly line actually makes a lot of sense. By using prepackaged, off-the-shelf battery systems with industry-leading power management capabilities, SpaceX is probably saving a huge amount of time, money, and effort. If the battery packs were already nearing the end of their useful automotive lives, the net cost could very well approach zero, aside from what looks like a minimal mounting brace. It’s possible that SpaceX has even pursued modifying and certifying large Tesla-derived battery packs for use on orbital Starship missions.
These battery packs were spotted by an eagle-eyed forum user who was first to recognize the hardware for what it likely was. Per the above photo, SpaceX appears to have joined two self-contained Tesla battery packs into single units that were then installed on a header tank. Knowing that the highest capacity Tesla offers is ~100 kWh, the 2×2 packs could store up to 400 kWh and offer instantaneous power output (ignoring thermal limitations) well into the megawatt (MW) range. It’s unclear if the first header tank also had batteries attached but SpaceX technicians began installing that tank inside Starship’s nose cone on the evening September 22nd. Tank #2 will likely follow in the next 24 hours per Musk’s indication that Starship Mk1 would be stacked to its full height on Wednesday.
For unknown reasons, SpaceX is choosing to mount the ~1000 kg (2200 lb) battery pack pairs directly onto the outside of one of Starship Mk1’s two header tanks. These tanks compliment the rocket prototype’s main propellant tanks and are meant to serve as small reserves of fuel (methane) and oxidizer (oxygen) that can be pressurized independently. During dramatic in-space and in-atmosphere maneuvers, the g-forces exerted on Starship could easily find the vehicle’s propellant pushed away from the ‘bottom’ of its main tanks, creating bubbles or voids that can damage and destroy rocket engines if ingested.
Pressurizing the entirety of the main tanks (a cylinder measuring 9m by ~40m or 30×130 ft) is extremely impractical – hence the need for much smaller header tanks. Falcon 9 boosters are able to sidestep this issue because they are small and light enough (relatively speaking) that cold gas thrusters can efficiently generate the positive Gs needed to safely ignite its engines for recovery and landing maneuvers. Empty, Starship alone will likely weigh no less than 4-6 times as much as a Falcon 9 booster (~25 tons, 55,000 lb).
According to CEO Elon Musk, SpaceX has decided to install those header tanks in the very tip of Starship Mk1’s conical nose to help balance out the vehicle’s center of mass. As a side-effect, SpaceX will have to install feed lines that run the entire length of the spacecraft and protect them with steel aero-covers. It’s unclear if this design choice is necessitated by Starship’s early, prototypical form or if – once outfitted with crew quarters or a functional cargo bay – it’s possible that that added mass will serve as enough of a counterbalance to preclude the need for ballast in the nose.
Musk posted a view inside an adjacent SpaceX fabrication facility in Boca Chica on September 23rd, showing a large row of staged steel sheets that will eventually be formed into aerodynamic shrouds for Starship Mk1’s raceways, fins, and wings.
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