Quote from: tleski on 01/04/2017 04:20 pmMatt Desch (Iridium CEO) confirmed yesterday on Twitter that the launch window will be instantaneous (see below).Not sure if it was obvious or not, so posting in the discussion thread.Na45597459: @IridiumBoss is Sunday's launch instantaneous or does it have a window?IridiumBoss: @Na45597459 Instantaneous. Need to launch to a specific plane (#6) and that's when it's overhead that day.https://twitter.com/iridiumboss/status/816018732262817793So F9 can't do yaw steering like Atlas V when launched out-of-plane?
Matt Desch (Iridium CEO) confirmed yesterday on Twitter that the launch window will be instantaneous (see below).Not sure if it was obvious or not, so posting in the discussion thread.Na45597459: @IridiumBoss is Sunday's launch instantaneous or does it have a window?IridiumBoss: @Na45597459 Instantaneous. Need to launch to a specific plane (#6) and that's when it's overhead that day.https://twitter.com/iridiumboss/status/816018732262817793
The hardware seems like it should be capable of doing this,
Quote from: LouScheffer on 01/04/2017 06:24 pmThe hardware seems like it should be capable of doing this,Based on what? Do you know the avionics architecture?
The second stage can do closed loop steering, or it could not get accurate insertion, or recover from a first stage problem, which it has demonstrated.
Determining the desired trajectory is quite straightforward compared to landing.
Quote from: LouScheffer on 01/04/2017 07:25 pmThe second stage can do closed loop steering, or it could not get accurate insertion, or recover from a first stage problem, which it has demonstrated.That has no bearing on the matter. Delta can not do yaw steering or launch windows for planetary missions, yet it can provide accurate insertion or recover from a first stage problem.
Quote from: Jim on 01/04/2017 07:38 pmQuote from: LouScheffer on 01/04/2017 07:25 pmThe second stage can do closed loop steering, or it could not get accurate insertion, or recover from a first stage problem, which it has demonstrated.That has no bearing on the matter. Delta can not do yaw steering or launch windows for planetary missions, yet it can provide accurate insertion or recover from a first stage problem. But this is a software limitation, not a hardware one, correct?
#SpaceX Falcon 9 return to flight finally planned on Monday Jan 9th, a little bird told me. Backup dates Jan 11 & 12th--Totally unconfirmed of course, but it played to my tapping of fingers against the desk waiting for word on F9 drinking RP-1.
Quote from: Robotbeat on 01/04/2017 07:40 pmQuote from: Jim on 01/04/2017 07:38 pmQuote from: LouScheffer on 01/04/2017 07:25 pmThe second stage can do closed loop steering, or it could not get accurate insertion, or recover from a first stage problem, which it has demonstrated.That has no bearing on the matter. Delta can not do yaw steering or launch windows for planetary missions, yet it can provide accurate insertion or recover from a first stage problem. But this is a software limitation, not a hardware one, correct?Don't you think they would have changed it by now if that were so?
But for SpaceX, it's almost surely software. The first stage is solving convex optimization in real time, a much harder task than yaw steering.
Quote from: LouScheffer on 01/05/2017 02:06 amBut for SpaceX, it's almost surely software. The first stage is solving convex optimization in real time, a much harder task than yaw steering. Not true. Targeting for yaw steering is harder. Again, the landing pad is a static target and always be in the same place no matter what time it is launched. Launching into a specific orbital plane at anytime within a launch window is much harder.
I see how for landing GPS sensing can help a lot. I don't see how GPS sensing helps with yaw steering because the orbital track we want to target is in motion from the perspective of a GPS reference frame.
Who says [GPS] helps for yaw steering?
Quote from: Robotbeat on 01/05/2017 05:00 amWho says [GPS] helps for yaw steering?You make my point for me! Someone implicitly asserted that since the first stage has precision descent guidance capability, then it would ipso facto "only" require software changes to give it yaw steering ascent capability.
I'm only suggesting it's unclear (to me) that the F9 ascent guidance system even has all the sensor inputs available to it that the Atlas yaw steering algorithm might be using. There's no public enumeration of the sensor inputs available to either, is there?
For example, a strap-down GPS aided INS system performing navigation relative to a fixed tangent plane frame-of-reference will typically:1. transform acceleration and angular rate measurements to platform coordinates;2. compensate the platform angular rate measurement for navigation frame rotation;3. integrate the compensated platform frame angular rates to maintain an accurate vector transformation from platform to navigation coordinates;4. transform platform frame accelerations to tangent plane using the transformation from step 3;5. integrate the (compensated) tangent plane accelerations to calculate tangent plane velocity and position;6. use the position estimate to predict the GPS observables;7. make GPS measurements, compute the residual error between the predicted and measured GPS observables, and use these measurement residuals to estimate and correct errors in the sensed and calculated INS quantities;8. transform the vehicle inertial measurements and state variables that are estimated above to frames-of-reference (e.g., body) that might be desired by other vehicle systems (e.g., control or mission planning).