Module model 

A rocket’s normal force and center of pressure: every component’s terms, built once from a Layout and summed at each flow condition.

The coefficient at an angle of attack α is C_N = C_Nα(α) α, with the slope defined as C_N/α (Niskanen 2009 eq. 3.8) and the center of pressure as the moment sum X = Σ C_Nα,i X_i / Σ C_Nα,i (Barrowman 1966 p. 38; Niskanen eq. 3.29). The terms:

• bodies of revolution, (2/A_ref)ΔA · sin α/α at X_B (crate::body), plus body lift η C_dn (A_plan/A_ref) sin² α / α at the planform centroid, Jorgensen’s crossflow term (crate::crossflow);
• a step in radius where one body component meets the next, (2/A_ref)ΔA · sin α/α at the joint, reported with the aft component. This extrapolates Barrowman 1966 eq. 10 over the whole body to a transition of zero length; Barrowman 1967 p. 18 assumes no discontinuities;
• fin sets, (C_Nα)₁ Σ sin² Λ_k · f_N · K_T(B) at the fin’s center of pressure, both at the flow’s Mach number (crate::fins::FinAero), and for one or two fins the side force (C_Nα)₁ Σ sin Λ cos Λ · K_T(B) across the flow’s plane (crate::fins::side_sum);
• tube fin sets, N ring wings’ slope at the ring’s center of pressure below Mach 0.8 (crate::tube_fins), with no roll dependence or side force.

Below the speed of sound the bodies’ potential-flow terms don’t change with Mach: slender-body theory’s slope and center of pressure hold at any Mach number (Barrowman 1967 p. 18). Body lift changes with the crossflow Mach number M sin α at any speed. Faster than sound, a pointed nose and the cylinders straight behind it take their potential-flow slope and moment from the second-order shock-expansion method (crate::shock_expansion, NACA TN 3527), and a boattail behind them Washington and Pettis’s measured increment (crate::supersonic_boattail), joined to slender-body theory linearly in Mach (SupersonicBody; the decision records on flying them, ADR-034 and ADR-037). Other bodies keep slender-body theory’s terms. BodyModel chooses the body-lift and boattail rules; the default is hpr’s current one.

Launch lugs and rail buttons add drag only, and internal parts sit inside the body. Any part kind this model doesn’t know is refused. Stations are meters aft of the nose tip.

Structs

AeroModel

A rocket’s aerodynamic model: normal force, center of pressure and drag.

BodyAero

A body component’s precomputed terms.

BodyModel

The choices in the bodies’ normal-force model (AeroModel::with_body_model). The default is hpr’s current model, BodyModel::CURRENT; BodyModel::BEFORE_M1_8E6 reproduces earlier results. Change one choice with BodyModel::with_body_lift, BodyModel::with_supersonic_boattail or BodyModel::with_supersonic_flare. In JSON, for example {"body_lift": {"kind": "galejs", "k": 1.1}, "supersonic_boattail": "footnote8"}; a missing field takes the current choice.

ComponentNormalForce

One component’s share of the normal force.

FinSetAero

A fin set’s precomputed terms.

Flow

The air-relative flow at one instant.

NormalForce

The normal force of a whole rocket, or of one component, at a flow condition.

PodFins

A pod’s fin set flown once per pod (FinSetAero::pods).

PodSetAero

A pod set’s precomputed terms: one pod’s body components, flown once per pod.

Roll

The whole rocket’s rolling moment coefficients at one Mach number (AeroModel::roll).

SupersonicBody

The second-order shock-expansion method’s share of each body component it covers, tabulated in Mach, and where it joins slender-body theory (the decision record on flying it, ADR-034).

Enums

SupersonicBoattail

How a boattail that the shock-expansion method covers takes its share of the normal force faster than sound (SupersonicBody).

SupersonicFallback

Why the shock-expansion method doesn’t fly a body faster than sound, so that slender-body theory flies it whole: the first switch along the body that stopped the run (AeroModel::supersonic_fallback, ADR-181). Each of the three named switches overstates the normal force’s lever arm (center of pressure aft) and has its issue.

SupersonicFlare

How a flare (a transition that widens the body) takes its share of the normal force faster than sound (SupersonicBody).

Constants

MAX_CANT_RAD

The largest fin cant the roll model takes, 15°: past it a fin stalls, where its lift stops growing with the angle, a judgement (AeroModel::roll).

NORMAL_FORCE_MACH_LIMIT

The top of the normal force’s range: Mach 5, where the hypersonic region begins (Niskanen 2009 Table 3.1, p. 19). AeroModel::normal_force refuses it and anything faster.

SUPERSONIC_JOIN_START_MACH

The lowest Mach number at which the body’s supersonic join can start (SupersonicBody): below it every body keeps slender-body theory’s terms. A judgement: the first body that TN 3527’s method covers and TN D-4014 measured is at Mach 1.5, the join’s end from here.

SUPERSONIC_JOIN_WIDTH_MACH

The width of the body’s supersonic join in Mach, 0.3: over it the shock-expansion shares replace slender-body theory’s linearly (SupersonicBody).