Module recovery 

Recovery devices: what opens, when it opens, and the drag area it presents.

A Device is a drag area (DeviceDrag) with a Trigger, a lag from the trigger to line stretch, and an Inflation law. A flight carries a list of them (crate::Simulation); the first one to open starts the descent phase (crate::Phase::Descent), where the rocket flies as a point mass under the sum of the open devices’ drag areas (docs/physics/recovery.md).

Streamers and tumbling bodies are drag areas too, from their own sources (StreamerModel, DeviceDrag::tumbling).

Canopy data comes from T. W. Knacke, Parachute Recovery Systems Design Manual, NWC TP 6575 (1991): drag coefficients on the nominal area S₀ from Tables 5-1 and 5-2, canopy fill constants from Table 5-6, the drag-area growth exponents of Pflanz’s method (Figure 5-51) and the infinite-mass opening-force coefficients C_x from the same tables. Every number is cited at its accessor, with the printed page.

Structs

BodyEvent

An event during a separated body’s descent, with the body at that instant.

BodyFlight

One separated body’s descent, from the moment it flies on its own to its landing.

BodySample

One separated body at an instant of its descent.

Device

A recovery device: a drag area, when it opens, and how it fills.

Separation

A separation: the stack comes apart at a stage boundary and every body descends under its own devices (docs/physics/recovery.md, and the decision record on separation, ADR-014).

Enums

CanopyType

A canopy type with printed data in Knacke’s tables.

DeviceDrag

What gives a device its drag area C_D S.

Inflation

How a device’s drag area grows once it is deployed.

StreamerModel

How a streamer’s drag area is estimated. A streamer of length l and width w has a planform (one-side) area S = l w and an aspect ratio AR = l/w.

Trigger

When a device’s charge fires.

Constants

MIN_STREAMER_ASPECT_RATIO

The smallest aspect ratio l/w a streamer may have. A strip wider than it is long is not a streamer, and both correlations run away there: Carruthers and Filippone’s C_D → ∞ as AR → 0, and appendix C notes its own form “obtains maximum drag for a fixed surface area at the limit l → 0, w → ∞” (printed page 117).

TUMBLE_BODY_DRAG_COEFFICIENT

The drag coefficient of a tumbling body tube, on its side profile area (the OpenRocket technical documentation v13.05, §3.5, printed page 54: fitted to 22 m drop tests of five models, and half the 1.12 of a circular cylinder in crossflow, as expected of a cylinder falling at a random angle).

TUMBLE_FIN_DRAG_COEFFICIENT

The drag coefficient of a tumbling fin set, on its effective fin area (the same source; it sits between a flat plate’s 1.17 and an open hemispherical cup’s 1.42, and the documentation says it is the less reliable of the two).

TUMBLE_FIN_EFFICIENCY

The effective fin area of a tumbling set is one fin’s area times this factor, by fin count (the same source, Table 3.4, printed page 55, for 1 to 8 fins). It is a fit, not a model: it is not n times one fin, and it is not monotonic.

Functions

terminal_speed_m_s

The equilibrium descent speed v_e = √(2 m g/(ρ C_D S)), m/s (Knacke, printed page 5-128).