Editing Falcon 1 (section)

===Second flight===
The second test flight was originally scheduled for January 2007, but was delayed because of problems with the second stage. Before the January launch date, SpaceX had stated earlier potential launch dates, moving from September 2006 to November and December. In December the launch was rescheduled for March 9, but delayed because of range availability issues caused by a [[Minuteman III]] test flight, which would re-enter over Kwajalein. The launch attempt on March 19 was delayed 45 minutes from 23:00 GMT because of a data-relay issue, and then scrubbed 1&nbsp;minute 2&nbsp;seconds before launch at 23:45 because of a computer issue, whereby the safety computer incorrectly detected a transmission failure caused by a hardware delay of a few [[millisecond]]s in the process. March 20 attempt was delayed 65 minutes from an originally planned time of 23:00 because of a problem with communications between one of the NASA experiments in the payload and the [[TDRS]] system.

The first launch attempt on March 21, 2007, was aborted at 00:05 GMT at the last second before launch and after the engine had ignited. It was, however, decided that another launch should be made the same day. The rocket successfully left the launch pad at 01:10 GMT on March 21, 2007, with a [[DemoSat]] payload for [[DARPA]] and [[NASA]]. The rocket performed well during the first-stage burn. However, during staging, the interstage fairing on the top of the first stage bumped the second-stage engine bell.<ref>{{cite web |url=http://www.spacedaily.com/reports/SpaceX_Confirms_Stage_Bump_On_Demoflight_2_999.html |title=SpaceX Confirms Stage Bump On Demoflight 2 |date=March 23, 2007 |author=Greg Zsidisin |publisher=Space Daily |access-date=June 24, 2017 }}</ref> The bump occurred as the second-stage nozzle exited the interstage, with the first stage rotating much faster than expected (a rotation rate of about 2.5°/s vs. expected rate of 0.5°/s maximum), thereby making contact with the [[niobium]] nozzle of the second stage. Elon Musk reported that the bump did not appear to have caused damage, and that the reason why they chose a niobium skirt instead of [[Reinforced carbon–carbon|carbon–carbon]] was to prevent problematic damage in the event of such incidents. Shortly after second-stage ignition, a stabilization ring detached from the engine bell as designed.<ref name="falconf2status">{{cite news |url=http://www.spaceflightnow.com/falcon/f2/status.html |title=Mission Status Center |date=March 20, 2007 |publisher=Space Flight Now }}</ref> At around T+4:20, a circular coning oscillation began, which increased in amplitude until video was lost. At T+5:01, the vehicle started to roll, and telemetry ended. According to [[Elon Musk]], the second-stage engine shut down at T+7:30 because of a roll-control issue. Sloshing of propellant in the LOX tank increased oscillation. This oscillation would normally have been dampened by the Thrust Vector Control system in the second stage, but the bump to the second-stage nozzle during separation caused an overcompensation in the correction.<ref name="falconf2status"/> The rocket continued to within one minute of its expected duration and also managed to deploy the satellite mass-simulator ring. While the webcast video ended prematurely, SpaceX was able to retrieve telemetry for the entire flight.<ref>{{cite web |url=https://www.nasaspaceflight.com/2007/03/falcon-i-flight-preliminary-assessment-positive-for-spacex/ |title=Falcon I flight – preliminary assessment positive for SpaceX |date=March 24, 2007 |author=Chris Bergin |publisher=NASAspaceflight |access-date=June 24, 2017 }}</ref> The status of the first stage is unknown; it was not recovered because of problems with a nonfunctioning GPS tracking device. The rocket reached a final altitude of {{convert|289|km|mi|abbr=on}} and a final velocity of 5.1&nbsp;km/s, compared to 7.5&nbsp;km/s needed for orbit.

SpaceX characterized the test flight as a success, having [[Technology readiness level|flight-proven]] over 95% of Falcon 1's systems. Their primary objectives for this launch were to test responsive launch procedures and gather data.<ref name="demoflight_2_launch_update_12"/> The SpaceX team planned both a diagnosis and solution vetted by third-party experts, believing that the slosh issue could be corrected by adding baffles to the second-stage LOX tank and adjusting the control logic. Furthermore, the Merlin shutdown transient was to be addressed by initiating shutdown at a much lower thrust level, albeit at some risk to engine reusability. The SpaceX team wished to work on the problem to avoid a recurrence as they changed over into the operational phase for Falcon 1.<ref name="Space28">{{cite web |url=https://www.space.com/3615-spacex-declares-falcon-1-rocket-operational-perfect-test.html |title=SpaceX Declares Falcon 1 Rocket Operational Despite Less than Perfect Test |date=March 28, 2007 |author=Brian Berger |publisher=Space.com |access-date=June 24, 2017 }}</ref>