SpaceX Starship (spacecraft)
Starship is a spacecraft and second stage under development by American aerospace company SpaceX. Stacked atop its booster, Super Heavy, the pair compose SpaceX's super heavy-lift space vehicle, also called Starship. The spacecraft is designed to transport both passengers and cargo to a variety of destinations, including Earth orbit, the Moon, and Mars. It is designed to be reusable and capable of landing propulsively by firing its engines to perform a controlled descent into the arms of a tower on Earth or with landing legs on other planetary bodies. It is intended to enable long-duration interplanetary flights with up to 100 passengers. It is also claimed by SpaceX to be capable of enabling travel to anywhere on Earth in under an hour. Furthermore, it has been proposed to be used to refuel other Starship spacecraft, enabling them to reach higher orbits and other space destinations. Elon Musk, the CEO of SpaceX, estimated in a tweet that eight launches would be needed to completely refuel a Starship in low Earth orbit. However, some estimates include as many as twenty refueling flights.
Development began in 2012, when Musk described a plan to build a reusable launch vehicle with substantially greater capabilities than the Falcon 9 and the planned Falcon Heavy. The rocket evolved through many design and name changes. On July 25, 2019, the Starhopper prototype performed the first successful flight at SpaceX Starbase near Boca Chica, Texas. In May 2021, the SN15 prototype became the first full-size test spacecraft to take off and land successfully. On April 20, 2023, Starship 24 performed the first full flight test on top of a Super Heavy booster, followed by a second test on November 18, 2023, when Starship 25 successfully completed hot staging and passed the Kármán line, becoming the first Starship to reach space as well as the heaviest object to ever reach space, before exploding at 148 km., SpaceX has conducted six more flight tests of Starship, successfully achieving orbital velocities and gradually testing the atmospheric reentry and vertical landing capabilities of the vehicle by performing controlled splashdowns into the Indian Ocean. In April 2024, Elon Musk announced two new versions of Starship, Block 2 and Block 3. Both versions are expected to be taller, and have increased thrust.
Design
The Block 2 version of Starship is tall, wide, and is composed of four general sections: the engine bay, the oxygen tank, the fuel tank, and the payload bay. The retired Block 1 was constructed in a similar manner, though it was only tall. Elon Musk stated in 2021 that the vehicle has a dry mass of roughly. The windward side is protected by a heat shield, which is composed of eighteen thousand hexagonal black tiles that can withstand temperatures of. It is designed to protect the vehicle during atmospheric entry and to be used multiple times with minimal maintenance between flights. The silica-based tiles are attached to Starship with pins, and had small gaps in between to allow for heat expansion. After flight test 4, SpaceX added a secondary ablative layer under the primary heat shield, though this was only added to the flaps of the flight test 6 vehicle. This ablative layer is likely composed of pyron, which is similar in composition to carbon composites. The total mass of the heat shield and ablative layer of a Block 1 ship is. After flight test 10, SpaceX added a felt, called "crunch wrap," between the gaps in between the tiles to prevent heat seeping in.Tanks
The propellant tanks on Starship are separated by a common bulkhead, similar to the ones used on the S-II and S-IVB stages on the Saturn V rocket. While Block 2 vehicles use an elliptical dome, the common and forward domes of the Block 1 design were more conical. Block 1 vehicles only had 24 stringers within the oxygen tank, while Block 2 vehicles had these added to the methane tanks. The vehicle's tanks hold of propellant, consisting of of liquid oxygen and of liquid methane.Fuel is fed to the engines via four downcomers, with three smaller downcomers feeding the Vacuum Raptors/RVacs and the central downcomer feeding the inner three engines. The central downcomer connects to a large sump, instead of directly to the methane tank itself. The original design only featured a single downcomer. The LOX downcomer extends into the LOX tank, with a small expanded portion of unknown purpose. Two additional downcomers route methane and oxygen from the header tanks. A camera is located on the walls of the tank, pointed towards the payload bay.
The oxygen tank terminates with the thrust structure of the vehicle. The RVacs are mounted directly to the aft dome, which has reinforcements mounted inside of the tank. The three sea level engines are mounted on the thrust puck, which forms the bottom of the aft dome. A conical steel structure is mounted inside the bottom of the dome, reinforcing the thrust puck enough to enable its support of the inner three engines. The propellant lines on the vehicles are all vacuum jacketed, reducing boiloff while in orbit.
Propulsion
Starship is powered by six Raptor engines, which are housed within a dedicated shielding compartment. Blocks 1 through 3 feature three sea-level engines, as well as three engines optimized for operation in the vacuum of space, called RVacs. Block 4 ships are expected to feature three additional RVacs. The sea-level engines are equipped with gimbal actuators, and reignite for the landing burns. After Starship's second flight test, this gimbaling system was switched from a hydraulic system to an electric one, enabling the removal of the hydraulic power units. This change was made to the booster after the first flight test. There are four engine chill lines onboard the vehicle, though two of these lines may serve another purpose.Each engine is protected by a dedicated shielding compartment. Beginning with S25, the Block 1 design had between 14 and 16 such vents. Additional vents were added after flight 7. The fire suppression system, which uses gaseous nitrogen to purge the engine bay during flight, was upgraded after flight 7. A similar system on the booster uses carbon dioxide to purge the individual engine compartments during flight and static fires.
The Raptor engine uses a full-flow staged combustion cycle, which has both oxygen and methane-rich turbopumps. Before 2014, only two full-flow staged-combustion rocket engine designs had advanced enough to undergo testing: the Soviet RD-270 project in the 1960s and the Aerojet Rocketdyne Integrated Powerhead Demonstrator in the mid-2000s. To improve performance, the engines burn supercooled propellant.
The Block 1 version of the ship produces a total of almost triple the thrust of the Saturn V second stage, with this being expected to increase to for Block 2 boosters and later up to with the Block 3 vehicle.
During unpowered flight in orbit, control authority is provided by cold gas thrusters fed with residual ullage gas. Four such thrusters are located just below the payload bay, and two on the oxygen tank. Near the top of the nosecone, there are two vents connected to the header tanks. Additional vents were added at the base of the vehicle after flight two.
Payload bay
The payload bay hosts the nosecone, header tanks, forward flaps, multiple COPVs, and the "PEZ dispenser". The header tanks are mounted at the tip of the payload bay. The LOX header tank forms the top of the nosecone, with the methane header tank attached directly below it. These tanks terminate in a conical sump, which are attached to the downcomers. Several COPVs are mounted in the space around the methane header tank, providing the startup gas for the engines, with twelve additional COPVs within the base of the payload bay.The nosecone has substantial internal reinforcement, mainly around the forward flap attachment points and lifting points for the chopsticks. The number of internal stringers was increased between Block 1 and Block 2 vehicles. Additional reinforcements are used to support the PEZ dispenser on ships equipped with one. Four Starlink antennas are located within the nosecone.
The PEZ dispenser is used to deploy Starlink satellites into LEO. It was first added to S24, though it was permanently sealed until flight 3. It consists of the dispenser mechanism and the door. The door opens by folding into the payload bay.
The dispenser itself is mounted directly to the forward dome. It has a truss structure for its base, with solid steel used elsewhere. A mobile track is used in the base, enabling the dispenser to push the satellite out of the vehicle. After dispensing a satellite, the next payload is lowered onto the base, and is deployed. The opposite occurs during loading, with the dispenser raising its payloads to receive another satellite. In order to prevent the satellite from floating out of the mechanism during zero-g operations, the dispenser locks the satellites in position using a "retention frame". This is lowered alongside the satellites during operation.
Flaps
Starship controls its reentry with four flaps, two aft flaps mounted to the sides of the engine bay and LOX tank and two forward flaps on the payload bay. Substantial reinforcements are present in the nosecone for the support of the forward flaps. According to SpaceX, the flaps replace the need for wings or tailplane, reduce the fuel needed for landing, and allow landing at destinations in the Solar System where runways do not exist. The flap's hinges are sealed in aerocovers because they would otherwise be easily damaged during reentry. Static wicks are present on the flaps, aiding in the discharge of static electricity.Despite this, damage to the forward flaps was observed on flights four, five, and six, with near complete loss occurring on flight 4. Beginning with Block 2, the design of these forward flaps was significantly changed, moving leeward and becoming thinner and angled. This sets them at an approximately 140-degree angle, compared to the 180-degree angle of the aft flaps and previous version of the forward flaps. This change was made to prevent the static aero from creating a tendency for the Ship to pitch up, even when the forward flaps were stowed, and also reduces the heating on the static aero and forward flaps observed on the last three flights of the Block 1 ship. Both sets of flaps feature cameras in their hinges.