<story><title>Boeing Starliner updates: Spacecraft flies into wrong orbit, jeopardizing test</title><url>https://www.cnbc.com/2019/12/20/boeings-starliner-flies-into-wrong-orbit-jeopardizing-trip-to-the-international-space-station.html</url></story><parent_chain><item><author>lokedhs</author><text>Running it on a timer actually works quite well. I don&amp;#x27;t know how this particular system actually works, but for example the Saturn V launch vehicle handled the initial navigation for several minutes from takeoff by executing previously calculated commands based on launch time, weather conditions etc.&lt;p&gt;Also, if I have understood things correctly, the lunar lander used a timer based approach to keep the rotation of the vehicle aligned with the surface of the moon as it orbited.&lt;p&gt;Since the orbital dynamics are very well understood and there really isn&amp;#x27;t anything that can affect the motion of the spacecraft other than engine burns, there doesn&amp;#x27;t seem to be any good reason to make it more complicated.</text></item><item><author>themgt</author><text>Boeing&amp;#x27;s explanation is that the flight automation software runs on some sort of &amp;quot;timer&amp;quot; and the timing apparently wasn&amp;#x27;t configured correctly, so Starliner thought it was at a different part of the mission and did the wrong burns.&lt;p&gt;Astonishing to me they make it sound like it runs like an independent stopwatch and not kept in sync with the actual IRL mission parameters in a more direct&amp;#x2F;continuous way. They&amp;#x27;re talking about the automation handover between the launch vehicle to the spacecraft, and on Starliner &amp;quot;clearly the time got messed up&amp;quot; ... &amp;quot;the spacecraft was not on the timer we expected it to be on&amp;quot;</text></item></parent_chain><comment><author>bufferoverflow</author><text>&amp;gt; &lt;i&gt;Since the orbital dynamics are very well understood and there really isn&amp;#x27;t anything that can affect the motion of the spacecraft other than engine burns&lt;/i&gt;&lt;p&gt;This is wrong.&lt;p&gt;1) Atmospheric drag (unless you&amp;#x27;re in really high orbits)&lt;p&gt;2) Wind&lt;p&gt;3) Uneven gravitational field. Our planet is not a perfect sphere. The moon is even less so.&lt;p&gt;4) Solar pressure (though very minor and kinda evens out in orbit).</text></comment>
<story><title>Boeing Starliner updates: Spacecraft flies into wrong orbit, jeopardizing test</title><url>https://www.cnbc.com/2019/12/20/boeings-starliner-flies-into-wrong-orbit-jeopardizing-trip-to-the-international-space-station.html</url></story><parent_chain><item><author>lokedhs</author><text>Running it on a timer actually works quite well. I don&amp;#x27;t know how this particular system actually works, but for example the Saturn V launch vehicle handled the initial navigation for several minutes from takeoff by executing previously calculated commands based on launch time, weather conditions etc.&lt;p&gt;Also, if I have understood things correctly, the lunar lander used a timer based approach to keep the rotation of the vehicle aligned with the surface of the moon as it orbited.&lt;p&gt;Since the orbital dynamics are very well understood and there really isn&amp;#x27;t anything that can affect the motion of the spacecraft other than engine burns, there doesn&amp;#x27;t seem to be any good reason to make it more complicated.</text></item><item><author>themgt</author><text>Boeing&amp;#x27;s explanation is that the flight automation software runs on some sort of &amp;quot;timer&amp;quot; and the timing apparently wasn&amp;#x27;t configured correctly, so Starliner thought it was at a different part of the mission and did the wrong burns.&lt;p&gt;Astonishing to me they make it sound like it runs like an independent stopwatch and not kept in sync with the actual IRL mission parameters in a more direct&amp;#x2F;continuous way. They&amp;#x27;re talking about the automation handover between the launch vehicle to the spacecraft, and on Starliner &amp;quot;clearly the time got messed up&amp;quot; ... &amp;quot;the spacecraft was not on the timer we expected it to be on&amp;quot;</text></item></parent_chain><comment><author>BurningFrog</author><text>When in stable orbit, I buy that argument.&lt;p&gt;But many things can go slightly wrong when firing all engines fighting your way up the atmosphere.</text></comment>