* SPACEX STARSHIP: On 20 April 2023, a SpaceX Starship heavily-lift booster performed its first all-up test flight. It lost several Raptor engines, went out of control, and was destroyed by range safety. It's nothing new for boosters to fail during development, and the fact that the Starship got off the ground was seen as encouraging.
Flight tests of what would become the Starship began in August 2019, with the brief up-&-down flight of the "Starhopper" demonstrators. The design subsequently evolved and became more ambitious from that time. As of the April 2023 flight, Starship was 120 meters (390 feet) tall 9 meters (30 feet) wide, and had a launch mass of about 5,000 tonnes (5,500 tons). Its standard configuration will have a lift capacity of 150 tonnes (330,000 pounds), with the expanded configuration having a capacity of 250 tonnes (550,000 pounds). While the prototype versions of Starship were not re-usable, Starship is designed to be fully re-usable.
Starship is primarily made of stainless steel. The big booster consists of a "Super Heavy" first stage and a "Starship" second stage, powered by "Raptor" and "Raptor Vacuum" engines. Raptor is a family of rocket engines developed by SpaceX. The Raptor burns liquid oxygen and methane in a highly efficient full-flow staged combustion power cycle. The engine is built mostly aluminum, copper and steel; oxidizer-side turbopumps and manifolds, subject to corrosive oxygen-rich flames, are made of an Inconel-like SX500 superalloy.
Raptor operates with an oxygen-to-methane mixture ratio of about 3.6:1, lower than the mixture ratio of 4:1 necessary to completely burn all propellants. Operation at the 4:1 ratio provides better performance in theory, but in practice usually results in overheating and destruction of the engine. The propellants leave the pre-burners and are injected into the main combustion chamber as hot gases instead of liquid droplets, enabling much higher power density as propellants mix more rapidly. The methane and oxygen are at such high temperatures and pressures that they ignite on contact, eliminating the need for igniters in the main combustion chamber.
At sea level, the standard Raptor engine produces 2.3 MN (236,000 kgp / 520,000 lbf) at a specific impulse of 327 seconds, increasing to 350 seconds in vacuum. [ED: Specific impulse is an index of the speed of rocket exhaust flow and engine fuel efficiency.] Raptor Vacuum, used on the Starship upper stage, is modified with a regeneratively cooled nozzle extension made of brazed steel tubes, increasing its expansion ratio [ED: the ratio of engine throat area to engine exit nozzle] to about 90 and its specific impulse in vacuum to 380 seconds. Another engine variant, Raptor Boost, is exclusive to the Super Heavy booster; the engine variant lacks thrust vectoring and has limited throttle capability, in exchange for increased thrust.
The first stage "Super Heavy" booster is 70 meters (230 feet) tall, 9 meters (30 feet) wide, and contains thirty-three Raptor engines arranged in concentric rings.[79] The outermost ring of 20 engines are of the "Raptor Boost" configuration, with gimbal actuators removed to save weight and a modified injector with reduced throttle performance in exchange for greater thrust. At max power, all engines produce a collective 75.9 MN (7,755,000 kgp / 17,100,000 lbf) of thrust.
The booster's tanks can hold 3,600 tonnes (7,900,000 pounds) of propellant, consisting of 2,800 tonnes (6,200,000 pounds) of liquid oxygen and 800 tonnes (1,800,000 pounds) of liquid methane. The final design will have a dry mass between 160 tonnes (350,000 pounds) and 200 tonnes (440,000 pounds).
The booster is equipped with four electrically actuated grid fins, each with a mass of 3 tonnes (6,600 pounds). Adjacent pairs of grid fins are only spaced sixty degrees apart instead of being orthogonal, as is the case on Falcon 9, to provide more control authority in the pitch axis. Also unlike Falcon 9, the grid fins do not retract and remain extended during ascent. During unpowered flight in vacuum, control authority is provided by cold gas thrusters fed with residual ullage gas -- ullage meaning the space in the tank voided as the fuel drains out.
The Starship second stage is 50 meters (160 feet) tall, 9 meters (30 feet) in diameter, and is fitted with 3 Raptor and 3 Raptor Vacuum engines for increased thrust in the vacuum. The booster's payload bay, measuring 17 meters (56 feet) tall by 8 meters (26 feet) in diameter, is of unprecedented size, with an internal volume of 1,000 cubic meters (35,000 cubic feet), which is more than the pressurized volume of the International Space Station. SpaceX also plans a "stretched" Starship with a payload bay 22 meters (72 feet) long. Payloads are deployed through doors on top of the payload bay. A dispenser rack can be installed to deploy multiple satellites.
Starship has a total propellant capacity of 1,200 tonnes (2,600,000 pounds). A set of reaction control thrusters, mounted on the exterior, control attitude while in space. The spacecraft has four body flaps to control the spacecraft's orientation and help dissipate energy during atmospheric entry; there are two forward flaps and two aft flaps. There are hardpoints under the forward flaps for lifting or catching the booster.
Starship's heat shield is designed to be used many times without maintenance between flights. It is composed of thousands of hexagonal black tiles that can withstand temperatures of 1,400 degrees Celsius (2,600 degrees Fahrenheit). The tiles are made of silica and are attached with pins, not glued; they are spaced with small gaps to deal with heat expansion.
For crewed flights, Starship will feature a pressurized crew section, with a life-support system, instead of a cargo bay. For long-duration missions, such as crewed flights to Mars, SpaceX describes the interior as potentially including "private cabins, large communal areas, centralized storage, solar storm shelters, and a viewing gallery". Starship's life support system will recycle resources such as air and water from waste.
The "Starship Human Landing System (Starship HLS)" is a crewed lunar lander variant of the Starship vehicle that is extensively modified for landing, operation, and take-off from the lunar surface. It features modified landing legs, a body-mounted solar array, a set of thrusters mounted mid-body to assist with final landing and take-off, two airlocks, and an elevator to lower crew and cargo onto the lunar surface. Starship HLS will be able to land more than 100 tonnes (220,000 pounds) of cargo on the Moon per flight.
Starship can be refueled by docking with separately launched Starship propellant tanker spacecraft in orbit. That would allow it to reach high-energy targets, such as geosynchronous orbit, the Moon, and Mars. A Starship propellant depot could cache methane and oxygen on-orbit; it will be used by Starship HLS.
* There have been two more all-up test flights since the April launch. The second flight was on 18 November 2023. First-stage flight was satisfactory, with the second stage igniting and continuing on track, though the first stage then exploded during recovery maneuvers. The second stage managed to leave the atmosphere, but telemetry was lost, and the booster then auto-destructed.
The third all-up test flight was on 14 March 2024. The booster took the second stage to altitude and the second stage successfully ignited, but the first stage then exploded during recovery maneuvers. The second stage successfully reached orbit, to then be lost during re-entry. The test flights were all regarded as partial successes, demonstrating incremental improvements on each flight; nobody expected that such an ambitious launch vehicle would work right away.
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