Starship is the name of the 2019 version of the second stage of the SpaceX reusable super heavy lift vehicle, resting upon the Super Heavy booster. The term "Starship" may also be used to refer to the complete stack of both stages as well, however.
2016 Interplanetary Transportation System
The origins of Starship are rooted in the Interplanetary Transportation System. This architecture was revealed in a 2016 speech by Elon Musk at the International Astronomical Congress. The concept was conceived as a two-stage spacecraft able to be reused a thousand times and to hold crews of over a hundred people with its primary intent to send people to Mars. The concept would depend upon tanker ships and orbital refueling, and it would extensively utilize in-situ resource utilization to produce the methane fuel required for the return voyage to Earth.
The design was immense with a twelve meter diameter and depended upon forty-two methane Raptor engines on the booster alone, allowing it to produce thrust of thirteen-thousand metric tons. The stacked system would measure one-hundred-twenty-two meters into the sky. Upon stage separation, the booster would return to the launch site, landing propulsively on the launch mounts so that the booster could quickly be refueled and again flown. The second stage, which in some launches would include a cabin, then had nine additional Raptor engines to accelerate the ship to Low Earth Orbit. In order to continue a trip to Mars, the second stage would have to be refueled by one or more tankers.
The proposal of the carbon fiber launch vehicle came with an estimated necessary cost of investment of ten billion dollars by Elon Musk, who suggested that a massive public-private partnership may be the best option for the vehicle. The original timeline of the proposal called for structures and propulsion development to complete in 2019, when ship testing and orbital testing were to begin. Orbital testing was to be completed in late 2022, and shortly thereafter Mars flights were to begin.
Musk acknowledged that this timeline was incredibly ambitious, but he believed that it was not too unreasonable. Musk took pride in announcing that two components of the system had already been built and were undergoing testing: the twelve-meter carbon fiber tank to store oxidizer in the second stage and the first development versions of the Raptor methane full-flow staged combustion engine. Initial tests of the carbon fiber tank proved to be successful, with Musk noting that his company had not "seen any leaks or major issues" when testing the tanks with cryogenic propellent. After heavy testing, the tank was destroyed in February 2017.
2017 Big Falcon Rocket
Over the course of a year, Musk and SpaceX recognized that a smaller, more feasible system was necessary to be pursued. Musk revealed the scaled-back design at the 2017 International Astronomical Congress almost exactly a year after the original unveil of the system. Musk also announced that the working name for the spacecraft was BFR, officially the Big Falcon Rocket. The height of the two-stage craft was reduced to one-hundred-six meters, and the diameter was reduced to nine meters.
2018 Starship-Super Heavy
It was presented by Elon Musk during the announcement of Yusaku Maezawa' Dear Moon project, as an evolution of the BFR/BFS concept and Interplanetary Transportation System (ITS) concepts.
2019 Starship-Super Heavy
Originally planned to be constructed of carbon fiber composite, it was changed to a Stainless Steel design in January 2019 .
Comparison of various iterations
|2016 ITS||2017 BFR||2018 Starship-Super Heavy||2019 Starship-Super Heavy|
|Height||122 m||106 m|
|Diameter||12 m||9 m||9 m||9 m|
|Principle material||Carbon fiber||Carbon fiber||Carbon fiber||301 Stainless steel|
|Thrust||128 MN||48 MN|
|Mass to Low Earth Orbit||300 T||150 T|
|Second stage engines|
85-120 tonnes mass, 9m diameter, 100-150 tonnes of payload to LEO, 100-150 tonnes to Mars. These are target values, the lower the mass of the vehicle, the higher the payload mass will be. Payload volume of 1000 m3.
3 vacuum Raptor engines with 380s ISP and 3 atmospheric Raptor engines with 330s ISP. Nominal thrust of 2000 kN, (200 tonnes of force per engine) These numbers are subject to change as the engine and the vehicle concepts are under development.
120-160 day transportation time to Mars, using aerocapture at Mars.
Fully reusable, rapid turnover and low maintenance vehicle.
Up to 100 passengers to Mars, although this has not been demonstrated yet by SpaceX.
The fundamental enabling technology of the Starship is supersonic retro propulsive landing on Mars. The use of supersonic retropropulsion in a critical phase of the Mars entry path allows the vehicle to land heavier payloads that previously thought possible. Although the exact details are not public, the current SpaceX Falcon 9 booster rocket has done flight tests that would confirm the flight path. 
A second enabling technology is the capacity of refueling in orbit.
A third enabling technology is the use of methane as fuel, than can be provided by In-situ ressources production systems on Mars, and therefore allow for the re-use of the spaceship.
A fourth technology is a robust heat shield for Mars and Earth entry. This allows for fast re-use and lower costs, but also for faster transit times, reducing the radiation exposure to travellers. The Spaceship is not intended to use low energy Hoffman transfer orbits, but higher velocity orbits. These have lower transit times but leave the vehicle with significant velocity when it reaches Mars or Earth. The Starship must then use direct entry and aerodynamic braking to shed the kinetic energy from the extra velocity.
The NASA Ames research center trajectory browser can be used to explore transit times to Mars and other bodies in the Solar System. Trajectory browser
- Musk, Elon. 2016. Making Humans a Multiplanetary Species. Guadalajara, Mexico.
- "Interplanetary Transport System". n.d. Spaceflight101.com. Accessed January 4, 2020.
- "First Development Tank for Mars Ship". 2016. Twitter. September 27, 2016.
- Mitchell, Jacob. 2016. "Here Is the inside of This Tank for You Guys!" Twitter. September 27, 2016.
- Musk, Elon. 2016. "SpaceX Propulsion Just Achieved First Firing of the Raptor Interplanetary Transport Engine". Twitter. September 26, 2016.
- Milberg, Evan. 2016. "SpaceX Successfully Tests Carbon Fiber Tank for Mars Spaceship". Composites Manufacturing. November 29, 2016.
- "Remains of the ITS Composite Tank in Anacortes, WA". 2017. r/SpaceXLounge on Reddit. February 17, 2017.
- Musk, Elon. 2017. Making Life Multiplanetary. Adelaide, Australia.
- Dodd, Tim. 2017. "2017 BFR vs 2016 ITS". Everyday Astronaut. September 29, 2017.
- Popular Mechanics article 
- AEROTHERMAL ANALYSIS OF REUSABLE LAUNCHER SYSTEMS DURING RETRO-PROPULSION REENTRY AND LANDING