Sample Return Capsule: Hyperbolic Reentry (2D)

Entry Parameters

Entry angle γ (below horizon) -8.0°

Capsule type

Release offset (targeting) 0 km

Live Telemetry

Standing by at the entry interface, 125 km altitude, 12.4 km/s. Set the entry angle and press Start.

Velocity

12.40 km/s

Altitude

125.0 km

Decel.

0.0 g

Downrange

0 km

Peak g

0.0 g

Heat flux

0 W/cm²

How it works

An asteroid sample capsule (Hayabusa2, OSIRIS-REx-style) is released from its mothership on a hyperbolic Earth-approach trajectory and hits the atmospheric interface (125 km) at roughly 12.4 km/s — direct entry, much faster than a capsule returning from low Earth orbit (~7.8 km/s), because it never stopped to orbit first.

Point-mass entry dynamics integrated every frame (exponential atmosphere, drag opposing velocity, inverse-square gravity), same model as the 3D version, drawn here as a side-view ground track instead of a 3D globe:

ρ(h)  = ρ₀·e^(−h/H)              H ≈ 8.5 km
D     = ρ(h)·v² / (2·B)          B = m/(Cd·A)  ballistic coefficient
g(h)  = g₀·(Rₑ/(Rₑ+h))²
dv/dt = −D − g·sin(γ)             (along the flight path)
q     = k·√ρ·v³                   Sutton–Graves heating approximation

Entry angle γ — too shallow (> −5°) and the capsule doesn't dip deep enough into the atmosphere to shed speed: it skips back out into space. Too steep (< −11°) and drag builds up too fast, the deceleration spikes past the capsule's structural limit (~55 g) and it fails.
Ballistic coefficient B — a heavier, denser capsule (higher B) decelerates later and deeper, a light one (lower B) decelerates earlier and higher up. "Heavy shield" trades a longer heat pulse for gentler peak g; "Light sampler" is the opposite.
Release offset — shifts where along the approach the capsule is released, which shifts its downrange entry point. The goal is to land inside the recovery ellipse without changing the physics of the descent itself.
Below ≈31 km and Mach ~1.5 a drogue chute deploys (B drops sharply); below ≈3.1 km the main chute deploys, slowing the capsule to a soft landing (<10 m/s).

Real-world relevance: OSIRIS-REx's capsule entered at 12.4 km/s on 24 Sep 2023 — the fastest reentry of a NASA capsule since Apollo — targeting the Utah Test and Training Range recovery ellipse; Hayabusa2 flew the same profile in 2020 for the Woomera range in Australia.

Entry interface: 125 km · 12.4 km/s
Target: recovery ellipse, 500–600 km downrange

Capsule trajectory Plasma / heating trail Recovery ellipse