Editing Luna 2 (section)

== Mission ==
=== Launch and trajectory ===
There was difficulty getting Luna 2 ready for launch. The first attempt on September 6 failed due to a loose electrical connection. A second attempt two days later also went awry when the core stage LOX tank failed to pressurize properly due to ice formation in a pressure sensing line. The ice plug was broken but the launch had to be called off again. By this point the RP-1 had been sitting in the propellant tanks for almost four days and there was the risk that it could start to paraffin-ize. The next attempt was made on September 9. Core and strap-on ignition began but the engines only reached 75% thrust. The launch was aborted and the RP-1 finally drained from the tanks. The DP-2 electrical switch had failed to send the command to open the engine valves to full throttle.{{Sfn|Harvey|2007|p=31}}The booster was removed from the pad and replaced with a different one, which was launched 12 September 1959, and ''Luna 2'' lifted off at 06:39:42 GMT.<ref name="nssse"/>{{efn|name="time"}}

Later in the month, Soviet premier [[Nikita Khrushchev]] was visiting the United States. The US space program had had several recent setbacks including an on-pad explosion of an Atlas-Able rocket and a [[Jupiter missile]] that exploded just after launch and killed several mice it was intended to fly on a biological mission. US President [[Dwight Eisenhower]], while meeting with Khrushchev, remarked that there had been a few failures of American rockets lately and asked if there had been similar problems in the Soviet space programme. Alluding to the abortive Luna 2 attempt two weeks earlier, Khrushchev replied that "We had a rocket we were going to launch, but it did not work correctly so they had to take it down and replace it with a different one."{{citation needed|date=December 2024}}

Once the vehicle reached Earth's [[escape velocity]], the upper stage was detached, allowing the probe to travel on its path to the Moon. ''Luna 2'' pirouetted slowly, making a full rotation every 14 minutes, while sending radio signals at 183.6, 19.993 and 39.986 [[megahertz|MHz]].{{Sfn|Harvey|2007|p=31}} The probe started transmitting information back to Earth using three different transmitters. These transmitters provided precise information on its course, allowing scientists to calculate that ''Luna 2'' would hit its mark on the Moon around 00:05 on 14 September ([[Moscow Time]]), which was announced on [[Radio Moscow]].{{Sfn|Harvey|2007|p=31}}

Because of claims{{whose|date=July 2024}} that information received from ''Luna 1'' was fake, the Russian scientists sent a [[telex]] to astronomer [[Bernard Lovell]] at [[Jodrell Bank Observatory]] at the [[University of Manchester]]. Having received the intended time of impact, and the transmission and trajectory details, it was Bernard Lovell who confirmed the mission's success to outside observers. However, the American media were still skeptical of the data until Lovell was able to prove that the radio signal was coming from ''Luna 2'' by showing the [[Doppler Shift|Doppler shift]] from its transmissions.{{Sfn|Harvey|2007|pp=32–33}}{{sfn|Lovell|1959|p=54}}

=== Lunar impact ===
[[File:Moon map Luna 17 Luna 2 Apollo 15 Surveyor 6 Surveyor 4 Luna 7 Luna 8 Luna 11.png|thumbnail|right|''Luna 2'' site is near the right of the image, relatively close to the [[Apollo 15]] landing site.]]

''Luna 2'' took a [[direct ascent|direct path]] to the Moon,{{Sfn|Reeves|2013|p=39}} starting with an initial velocity from Earth of {{convert|11.2|km/s|mph}}{{Sfn|Harvey|2007|p=31}} and impacting the Moon at about {{convert|3.3|km/s|mph}}.{{sfn|Corda|2017|p=47}} It hit the Moon about 0° west and 29.1° north of the centre of the visible disk at 00:02:24 (Moscow Time) on 14 September 1959.{{sfn|Moore|Rees|2014|p=40}}{{Sfn|Harvey|2007|p=33}}{{efn|name="time"}} The probe became the first human-made object to hit another celestial body.<ref>{{cite web|url=http://www.planetary.org/explore/space-topics/space-missions/missions-to-the-moon.html#luna2|title=Missions to the Moon|publisher=The Planetary Society|access-date=12 March 2019}}</ref> To provide a display visible from Earth, on 13 September the spacecraft released a vapour cloud that expanded to a diameter of {{convert|650|km|mi}} that was seen by observatories in [[Alma Ata]] in Kazakhstan, [[Byurakan]] in Armenia, [[Abastumani]] and [[Tbilisi]] in Georgia, and [[Stalinabad]] in Tajikistan.{{Sfn|Harvey|2007|p=31}} This cloud also acted as an experiment to see how the sodium gas would act in a vacuum and zero gravity.<ref name="nasa1"/> The last stage of the rocket that propelled ''Luna 2'' also hit the Moon's surface about 30 minutes after the spacecraft, but there was uncertainty about where it landed.<ref name="nasa1"/>

Bernard Lovell began tracking the probe about five hours before it struck the Moon and also recorded the transmission from the probe, which ended abruptly. He played the recording during a phone call to reporters in New York to finally convince most media observers of the mission's authenticity.{{Sfn|Harvey|2007|p=33}}