Beresheet

Spacecraft Design

Beresheet was a compact spacecraft built around a boxy central structure mounted on a circular deck supported by four reverse-tripod landing legs. Its exterior was covered with gold multi-layer insulation (MLI) for passive thermal protection. The assembled lander stood approximately 1.5 m tall and about 2.3 m wide, a scale commonly compared to a domestic washing machine. Launch mass was approximately 585–600 kg fully fueled; dry mass was approximately 150–180 kg, with propellant making up the bulk of the launch mass.

The propulsion system was developed by IAI. It used monomethylhydrazine (MMH) fuel with mixed oxides of nitrogen (MON) as the oxidizer, a hypergolic bipropellant combination. The main engine was a LEROS 2b restartable liquid-propellant engine, used for all major maneuvers: Earth-orbit apogee raising, lunar orbit insertion, descent braking, and the planned landing. Eight smaller thrusters handled attitude control and minor trajectory corrections.

Beresheet had no active thermal control system, relying entirely on passive methods. This imposed a planned surface lifetime of approximately two days, after which the lander was expected to overheat as the lunar day advanced. The spacecraft's design reflected a deliberate emphasis on low cost and low mass, which also meant limited redundancy — a design trade-off that SpaceIL executives acknowledged increased vulnerability to single-point failures.

Mission operations were conducted from a control center in Yehud, Israel, southeast of Tel Aviv, operated jointly by SpaceIL and IAI. The ground segment used seven stations worldwide to maintain communications during flight and lunar orbit.

Descent Failure

The failure of the landing attempt resulted from a chain of events triggered by a hardware fault. During the powered descent on 11 April 2019, an inertial measurement unit (IMU) — a sensor that provides acceleration and orientation data essential for guidance, navigation, and control — failed. SpaceIL and IAI officials, including Opher Doron, general manager of IAI's space division, publicly stated that the IMU failure initiated an "unfortunate chain of events" that caused the main LEROS 2b engine to shut down.

The first anomaly was detected at approximately 14 km altitude. Mission controllers succeeded in restarting the main engine, but by the time it resumed thrust the spacecraft had already accumulated too much vertical velocity at too low an altitude to decelerate to a safe speed. At the point of final loss of contact — approximately 150 m above the surface — the lander's vertical speed was approximately 500 km/h toward the Moon. Impact followed shortly thereafter. NASA's Lunar Reconnaissance Orbiter subsequently imaged the crash site in Mare Serenitatis, confirming a dark, elongated mark consistent with a high-speed impact.

SpaceIL's pre-mission design philosophy prioritised low cost and low mass, resulting in limited redundancy across critical systems. This approach — a conscious trade-off given the mission's budget — meant that a single IMU failure could propagate without backup systems compensating, as ultimately occurred during the final descent.

Funding and Development

The total cost of the Beresheet mission, including launch, was approximately US $90–100 million. The project was co-developed by SpaceIL, a non-profit organisation formed to compete in the Google Lunar XPRIZE, and Israel Aerospace Industries, which served as the prime spacecraft contractor and contributed substantial engineering and manufacturing support.

Almost all funding came from private donors and corporate sponsors. The single largest contributor was Morris Kahn, who provided approximately US $40 million. Other major donors included Miriam and Sheldon Adelson, Sami Sagol, Lynn Schusterman, Stephen Grand, and Sylvan Adams, along with contributions from the general public via crowdfunding. The Israeli government, through the Israel Space Agency, contributed approximately US $2 million in cash — roughly 2% of the total — alongside technical support.

Tardigrades and Planetary Protection

Among the contents of the Arch Mission Foundation's Lunar Library were thousands of desiccated tardigrades (microscopic animals also known as water bears) in a dehydrated tun state, along with human DNA samples. Arch Mission Foundation founder Nova Spivack assessed after the crash that the nickel-plate library was likely mostly or wholly intact, meaning the tardigrades and DNA are probably present at the crash site in Mare Serenitatis.

In their tun state, tardigrades halt metabolism and can tolerate vacuum, radiation, and extreme temperatures for extended periods. Laboratory testing has shown survival after impacts at speeds up to approximately 2,600 km/h, and Beresheet's impact speed was lower than that threshold. However, conditions at the lunar surface — hard vacuum, intense solar ultraviolet and cosmic radiation, and temperature swings from roughly −170 °C at night to over +100 °C during the day, combined with the total absence of liquid water, oxygen, or food — preclude any revival or reproduction. Scientific assessments have concluded that the tardigrades cannot reactivate on the Moon, let alone colonise it.

Under the 1967 Outer Space Treaty, states are required to avoid harmful contamination of celestial bodies, but the Moon is not subject to the stringent planetary-protection requirements applied to potentially habitable worlds such as Mars. NASA's planetary-protection framework classifies the Moon as presenting minimal contamination concern, and because Beresheet was a private non-NASA mission to a non-habitable body, the presence of dehydrated tardigrades is not treated as a planetary-protection violation. The episode has nonetheless generated ongoing discussion among researchers about the ethics of depositing Earth biological material on other worlds without broad international consensus, and is frequently cited as an example of why planetary-protection norms may need updating to address the growing commercial spaceflight sector.

Legacy and Achievements

Despite the loss of the spacecraft during landing, Beresheet achieved several significant milestones. It was the first Israeli mission to reach lunar orbit, making Israel the seventh nation to do so. It was the first attempt by a private organisation to land on the Moon, and it remains one of the smallest spacecraft ever to travel from Earth orbit to the lunar vicinity. The mission demonstrated that a compact, commercially procured spacecraft could independently execute the complex series of orbit-raising maneuvers and translunar injection required to reach the Moon.

The mission's educational impact — the "Beresheet effect" — was a stated primary goal alongside the scientific objectives. SpaceIL reported a measurable increase in Israeli students' interest in science, technology, engineering, and mathematics following the mission. SpaceIL subsequently announced plans for a follow-on mission, Beresheet 2, though that effort encountered significant funding challenges.