1. Description

2. Prototypes
     Starship test flight rocket    Starship orbital prototype    Testing  

3. Intended uses

4. References

Two {{convert|9|m|ft|sp=us|abbr=on|adj=on}}-diameter stainless steel Starship test articles are being built, and one had already begun integrated system testing by March 2019. The Starship test flight rocket—Starhopper—will be used for initial integrated testing of the Raptor rocket engine with a flight-capable propellant structure as well as for low-altitude, low-velocity flight testing of launches and landings. It began hotfire testing in April.^[3] A second test article, the Starship orbital prototype is planned to be used after mid-2019 for high-altitude, high-velocity testing.^[4] Integrated system testing of Starhopper, including the first flight test, began in April 2019.

Description

Unusual for previous launch vehicle and spacecraft designs, Starship is to function as both a second stage for the BFR launch vehicle that provides acceleration to orbital velocity on all launches from Earth, and yet will also be used in space as an on-orbit long-duration spacecraft.^[3][6]

The Starship design is intended to be fully reusable even when used as a second stage for orbital ascent from Earth. Starship is being designed so as to be capable of reentering Earth's atmosphere from orbital velocities and landing vertically, with a design goal of rapid reusability.

In the 2018 design, Starship will use seven sea-level rated Raptor engines, identical engines as used on the first-stage of the BFR launch vehicle, Super Heavy.^[3] Subsequent versions for interplanetary travel are expected to utilize a vacuum-optimized Raptor engine variant to optimize specific impulse (I_sp).

• spaceship: a large, long-duration spacecraft capable of carrying passengers^[4] or cargo to interplanetary destinations, to LEO, or between destinations on Earth.
• tanker: a cargo-only propellant tanker to support the refilling of propellants in Earth orbit. The tanker will enable launching a heavy spacecraft to interplanetary space as the spacecraft being refueled can use its tanks twice, first to reach LEO and afterwards to leave Earth orbit.
• satellite delivery spacecraft: a vehicle with a large cargo bay door that can open in space to facilitate the placement of spacecraft into orbit, or the recovery of spacecraft and space debris.

Major characteristics of Starship include:^[5][4][6][7]

• being designed such that the ship can return from Earth orbit and land near the launch mount using retropropulsive landing and the reusable launch vehicle technologies developed earlier by SpaceX
• landing reliability is projected by SpaceX to ultimately be able to achieve "airline levels" of safety due to engine-out capability.
• rendezvous and docking operations will be automated
• on-orbit propellant transfers from Starship tankers to Starship spaceships or cargo spaceships
• a Starship and its payload will be able to transit to the Moon or fly to Mars after on-orbit propellant loading
• Stainless steel structure and tank construction. Its strength-to-mass ratio is comparable to or better than the earlier SpaceX design alternative of carbon fiber composites across the anticipated temperature ranges, from the low temperatures of cryogenic propellants to the high temperatures of atmospheric reentry^[8]
• some parts of the craft will be built with a stainless steel alloy that "has undergone [a type of] cryogenic treatment, in which metals are ... cold-formed/worked [to produce a] cryo-treated steel ... dramatically lighter and more wear-resistant than traditional hot-rolled steel."^[8]
• the thermal protection system against the harsh conditions of atmospheric reentry will utilize a double stainless-steel skin with active coolant flowing in between the two layers. Hexagonal stainless steel tiles will blanket the windward side of Starship, and some areas will additionally contain multiple small pores that will allow for transpiration cooling.^[3][9][10]
• as envisioned in the 2017 design unveiling, the Starship is to have a pressurized volume of approximately {{cvt|1000|m3|ft3}}, which could be configured for up to 40 cabins, large common areas, central storage, a galley, and a solar flare shelter for Mars missions plus 12 unpressurized aft cargo containers of {{cvt|88|m3|ft3}} total.^[7]
• flexible design options; for example, a possible design modification to the base Starship—expendable 3-engine Starship with no fairing, canards, rear fins, nor landing legs—to optimize mass ratio for interplanetary exploration with robotic probes.^[11]

When Starship is used for BEO launches to Mars, the functioning of the overall expedition system will necessarily include propellant production on the Mars surface. This is necessary for the return trip and to reuse the spaceship to keep costs as low as possible. Lunar destinations (circumlunar flybys, orbits and landings) will be possible without lunar-propellant depots, so long as the spaceship is refueled in a high-elliptical orbit before the lunar transit begins.^[4] Some lunar flybys will be possible without orbital refueling as evidenced by the mission profile of the SpaceX lunar tourism mission.^[12]

Prototypes

Two test articles were being built by March 2019. The low-altitude, low-velocity Starship test flight rocket was used for initial integrated testing of the Raptor rocket engine with a flight-capable propellant structure, and will test the newly-designed autogenous pressurization system that is replacing traditional helium tank pressurization as well as initial launch and landing algorithms for the much larger 9-meter-diameter rocket. SpaceX originally developed their reusable booster technology for the 3-meter-diameter Falcon 9 from 2012–2018. It will also be the platform for the first flight tests of the full-flow staged combustion methalox Raptor engines, where the hopper vehicle is expected to be flight tested with up to three engines to facilitate engine-out tolerance testing.^[3]

The high-altitude, high-velocity Starship orbital prototype will be used to develop and flight test novel thermal protection systems and hypersonic reentry control surfaces.^[3] The orbital prototype is expected to be outfitted with more than three Raptor engines.

Starship test flight rocket

The construction of the initial test article—the "Starship test flight rocket,"^[13] "test hopper,"^[29] or "Starhopper"^[14][15]—was begun in early December 2018 and the external frame and skin was complete by 10 January 2019. Constructed outside in the open on a SpaceX property just two miles from Boca Chica Beach in South Texas, the external body of the rocket rapidly came together in less than six weeks. Originally thought by watchers of construction at the SpaceX South Texas Launch Site to be the initial construction of a large water tower, the stainless steel vehicle was built by welders and construction workers in more of a shipyard form of construction than traditional aerospace manufacturing. The full Starhopper vehicle is {{convert|9|m|sp=us}} in diameter and was originally {{convert|39|m|sp=us}} tall in January 2019.^[16][8] Subsequent wind damage to the nose cone of the vehicle resulted in a SpaceX decision to scrap it, and fly the low-velocity hopper tests with no nose cone,{{cn|date=March 2019}} resulting in a much shorter test vehicle.

From mid-January to early-March, a major focus of the manufacture of the test article was to complete the pressure vessel construction for the liquid methane and liquid oxygen tanks, including plumbing up the system, and moving the lower tank section of the vehicle two miles to the launch pad on 8 March.^[17]

The test article will be used to flight test a number of subsystems of the Starship and will be used to expand the flight envelope as the Starship design will be finalized.^[16][18][19]

Initial tests began in March 2019, flight tests are expected for April.^[20]

All test flights of the "test hopper"^[16] will be low altitude, under {{convert|5|km|ft|sp=us}}.^[21] On 3 April 2019, SpaceX conducted a successful static fire test in Texas of its Starhopper vehicle, which ignited the engine while the vehicle remained tethered to the ground.^[22] See Testing section, below, for full testing history and details.

Starship orbital prototype

A second prototype was begun by December 2018 when subsections of a Starship orbital prototype—also referred to as the "Starship Mk I orbital design"—were under construction in San Pedro, California.^[23] Planned for high-altitude and high-velocity testing,^[24]

the orbital prototype will be taller than the suborbital hopper, have thicker skins, and a smoothly curving nose section.^[25]

By March 2019, construction of the full external structure and propellant tanks of the orbital prototype was well underway at the SpaceX "ad-hoc South Texas ‘shipyard’," with an expectation that the vehicle could be complete and ready to begin testing as early as June.^[26]

The new build of additional 9-meter diameter stainless steel structures in South Texas in late February was originally misattributed and thought to be a second and more substantial version of the Starhopper's upper section, following the destruction of the first Starhopper upper section, damaged by high coastal winds in January.^[17]

Testing

Integrated system testing of the first Starship prototype (Starhopper)—with the newly-built ground support equipment (GSE) at the SpaceX South Texas facilities— began in March 2019.

"These tests involved fueling Starhopper with LOX and liquid methane and testing the pressurization systems, observed via icing of propellant lines leading to the vehicle and the venting of cryogenic boil off at the launch/test site. ... During a period of over a week, StarHopper underwent almost daily tanking tests, WDRs and a few pre-burner tests."^[3]

The first static fire test of the Starhopper test vehicle, with only a single Raptor engine attached, occurred on 3 April 2019. The firing was a few seconds duration, and was classed as successful by SpaceX.^[27]

A second tethered test followed just two days later, on 5 April.^[28]

Intended uses

Starship is intended to become the mainline SpaceX orbital vehicle, as SpaceX has announced it intends to fully replace its existing Falcon 9 launch vehicle and Dragon space capsule fleet with Starship/Super Heavy during the early 2020s.^[30][4][54]{{rp|24:50–27:05}}

• legacy Earth-orbit satellite delivery market. In addition to the standard external launch market that SpaceX has been servicing since 2013, the company intends to use Super Heavy/Starship to most cost-effectively launch the largest portion of its own satellite internet constellation, Starlink, with more than 12,000 satellites intended to be launched by 2026, more than six times the total number of active satellites on orbit in 2018.^[31]
• long-duration spaceflights in the cislunar region
• Mars transportation, both as cargo ships as well as passenger-carrying transport
• long-duration flights to the outer planets, for cargo and astronauts^[32]

In addition, SpaceX has mentioned the theoretical ability of using a boosted Starship to carry passengers on suborbital flights between two points on Earth in under one hour, providing commercial long-haul transport on Earth, competing with long-range aircraft.^[33][34] However, SpaceX has announced no concrete plans to pursue this use case.^[35][18][36]

References

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