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Nolan Holden edited this page Aug 12, 2017 · 3 revisions

Current development: Latent Flight-phase analysis and (eventually) flight command and control.

Vehicle Flight Phases

(Assuming two-stage)

  • Pad
  • Thrust 1 ---> Stage 1 fuel depleted
  • Coast 1 Unseparated ---> Stage separation
  • Coast 1 Separated ---> Stage 2 ignition
  • Thrust 2 ---> Stage 2 fuel depleted
  • Coast 2 ---> (potentially* vehicle apogee) ---> (Drogue parachute deploys)
  • Drogue Parachute Deployed ---> Main parachute deploys
  • Main Parachute Deployed
  • Vehicle Landed

* Drogue chute can potentially deploy prior to apogee

Note: There exists no guarantee that the vehicle executes any of these events successfully. Much of the design here will require consideration of that fact.

Excluding the transition events, which can be considered to be instantaneous transitions between the flight phases, we have:

  • Pad
  • Thrust 1
  • Coast 1 Unseparated
  • Coast 1 Separated
  • Thrust 2
  • Coast 2
  • Drogue Deployed
  • Main Deployed
  • Landed

PAD

  • Pad Altitude
    • Periodically (say, every 200ms) set the pad altitude to the current sensed altitude unless any of the following are true:
      • the vehicle is experiencing an acceleration higher than a nominal, "at-rest" level[1]. If so, direct the next [few] checks[2] to see if that high acceleration subsides without a significant altitude delta[3].
      • the current altitude is beyond a altitude delta[4] from the stored pad altitude.

Pre-Flight (i.e., compile time) Constants:

  • [1] kHigherThanNominalAccelerationThreshold: kHigherThanNominalAccelerationThreshold = kNominalAcceleration * kNominalAccelerationCoefficient where kNominalAccelerationCoefficient is greater than 1.0 and probably less than 1.1 and where kHigherThanNominalAccelerationThreshold and kNominalAcceleration are given by the same units.
  • [3] kLiftoffAltitudeDelta: kLiftoffAltitudeDelta =

[2] Recall that we are currently restricted to a single thread. This restraint requires that none of these checks lock the thread for very long. Specifically, we will disallow any thread sleeping (i.e., delay(...); ). when we wish to continue checking for a condition. Instead, we still immediately release the thread back to the caller but set a flag (or flags) to direct the corresponding additional checks in the following update calls as needed.)

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