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"  Historically, first flights of new expendable launch systems often go awry, though engineers with much more design experience and ability to simulate systems have good track records. So while SpaceX obviously wanted to demonstrate the ability to deliver a dummy payload to orbit with the first flight of its Falcon 9 last Friday, it was a test flight, with a number of objectives. Even if it hadn&amp;#039;t achieved that ultimate orbital goal, just meeting the lesser goals would still have constituted a successful test.  The first-flight-test goal was to gather as much data as possible, however long the flight lasted, to provide guidance for any needed design changes. But beyond that, they had a number of specific events that each progressively proved out their initial design and gave them data on actual vehicle performance that engineers can now match against their predictions from simulations. Here&amp;#039;s how the flight went, in detail. T-minus 2:00:00\u2014The False Start Even before liftoff, the SpaceX launch team inadvertently demonstrated one capability designed into the vehicle that it hadn&amp;#039;t planned to\u2014the ability to do an on-pad abort after ignition and quickly recycle and launch within 2 hours. With only an hour and a half left in the flight&amp;#039;s daily launch window, on its first attempt, right after the engines lit, one of them showed a parameter out of specification, and the whole system shut down and saved itself automatically. After spending a few minutes analyzing the problem, the launch crew decided that the tolerance on that parameter was simply too conservative, widened it somewhat and made another launch attempt\u2014this time successful, with 15 minutes to spare. This was in fact one of the most impressive things about the launch, because almost any other vehicle would have had to detank after such an abort and cycle for at least 24 hours (this is the case with the space shuttle). It was a good demonstration of both the robustness of the operations and design and the team&amp;#039;s knowledge of its vehicle. &amp;amp;gt; T-plus 0:00:03\u2014All Engines, Clearing the Gantry and an Unplanned Roll In terms of planned flight-test (and later operational) milestones, the first was a successful lighting of all nine engines at T-minus 0:00:01, and release of the clamps for liftoff at T-plus 0:00:00. This went as planned. The next goal was to clear the gantry, which occurred at approximately T-plus 0:00:06 with what looked to be a slight unplanned roll (that is, about its long axis) of the vehicle, though that didn&amp;#039;t seem to affect the performance in any significant way. According to SpaceX, this was caused by an initial torque bias by exhaust from the gas generators of the engines and the spiral windings of the nozzles, and will be tuned out in future flights. T-plus 0:01:22\u2014Maximum Pressure A very crucial milestone occurred a little over a minute into the launch\u2014maximum dynamic pressure, or Max Q for short, was reached. The dynamic pressure is a function of both ambient air pressure and vehicle speed. The ambient pressure decreases with altitude, but speed increases as the rocket accelerates. Initially Q is low, even though the pressure is maximum at sea level, because the vehicle is moving slowly. But as it ascends and picks up speed, Q increases. At a certain point, though, the air starts to thin out, and Q starts to decrease again, even with the increase in speed. The point at which this occurs is Max Q, and it&amp;#039;s what the vehicle structural engineer must design for. Once past it, air drag and stress from it become ever-decreasing factors until they disappear entirely as the rocket leaves the atmosphere. The other thing that happens as the vehicle ascends is that the exhaust starts to expand more as the air pressure against which it pushes continues to decrease, which also improves performance. T-plus 0:03:04\u2014Stage Separation and First Stage Re-Entry After Max Q, the next critical event\u2014and one that has caused the failure of many launches\u2014is stage separation, and then second-stage ignition. This cannot occur, however, until MECO (Main Engine Cut Off), because you don&amp;#039;t want to have the lower stage &amp;quot;chasing&amp;quot; the upper one after they separate. MECO occurred a little over 3 minutes into the flight, at T-plus 0:03:05, with a clean separation 4 seconds later, by the release of pneumatic latches. Three seconds after that, the Merlin engine (the same kind as the nine in the first stage) in the second stage ignited, continuing the journey to orbit. The separated first stage was then supposed to enter the atmosphere, where chutes would open and it could be recovered in the Atlantic for flight forensics and possibly to reuse some components. Unfortunately, it broke up on entry, with no chutes opening and little to recover except a debris field on the surface. This was probably the most significant failure of the flight, but it won&amp;#039;t hold up the program in any way. It is not a mission-critical capability, because it isn&amp;#039;t necessary to recover first stages to get to orbit. Of course, if this problem can&amp;#039;t be fixed, every launch will cost more because the stages won&amp;#039;t be able to be reused. SpaceX will focus attention on this failure in every flight going forward until the engineers either get it right or give up and remove the recovery systems to allow additional payload. T-plus 0:08:50\u2014Orbital Delivery After an Unplanned Roll Meanwhile, back up in space, the second-stage engine burned for another five and a half minutes or so, steadily increasing the velocity of the second stage to that needed to attain Earth orbit (about 17,000 mph). There was a slight problem visible in the video, with what looked to be another unplanned roll, this time of the upper stage, with an increasing rate as it ended the burn (presumably because the moment of inertia was decreasing as the propellants were emptied from the tanks, with a constant torque from some unknown source, perhaps venting from the gas generator or turbopump exhaust). It never reached a dangerous level, appearing to be less than a revolution per second, and the payload (a Dragon capsule structural test article) was delivered into the planned orbit, with an inclination of 34.5 degrees, 148-mile perigee and 165-mile apogee, at T-plus 0:08:51. SpaceX still doesn&amp;#039;t know the cause of the roll but is continuing to investigate. "^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.popularmechanics.com/space/rockets/a5852/spacex-falcon9-first-flight/>