← INDEX — FIG. 00 — 3 JANUARY 2019, VON KÁRMÁN CRATER L2 · 1,731 g · 1,935.3 g

RABBIT
CHANG'E AND THE FAR SIDE OF THE MOON

China's lunar programme: orbit, land, return — and then the far side.

BEGIN — CHAPTER 01 →

CH.01 / 10 — STEP ONE: CIRCLE THE MOON

Two orbiters, a map and an asteroid

The programme had three phases: orbit, land, return.

Chang'e 2 mapped the Moon and flew past Toutatis at 1.9 km.

CH.02 / 10 — STEP TWO: LAND, AND DRIVE

Chang'e 3: the first soft landing in thirty-seven years

Chang'e 3 landed in Mare Imbrium in December 2013.

Yutu was a 140 kg rover; a backup set of hardware remained.

CH.03 / 10 — THE SIDE WE NEVER SEE

One turn per orbit: why the far side has no view of Earth

The Moon is tidally locked; the far side never faces Earth.

Toggle the spin below.

CH.04 / 10 — A BRIDGE OF MAGPIES

Queqiao: a relay that must never sit still

Queqiao went to the Earth–Moon L2 point.

At exactly L2 the relay would be hidden behind the Moon; it flies a halo orbit.

THE COLLINEAR POINT L2 (CIRCULAR RESTRICTED THREE-BODY PROBLEM)

γ⁵ + (3 − μ)γ⁴ + (3 − 2μ)γ³ − μγ² − 2μγ − μ = 0 · μ = M_Moon / (M_Earth + M_Moon) ≈ 0.01215

γ: distance Moon–L2 in Earth–Moon units.

RELAY OFFSET FROM THE EARTH–MOON LINE—

Vertical stretched ×8.

CH.05 / 10 — THE FIRST LANDING ON THE FAR SIDE

Chang'e 4 and Yutu-2 in the oldest, deepest basin

Chang'e 4 landed in Von Kármán crater in January 2019.

Yutu-2 found possible mantle-derived material.

CH.06 / 10 — STEP THREE: BRING IT HOME

Chang'e 5: four spacecraft, one rendezvous, 1,731 grams

Chang'e 5 flew four craft in one.

1,731 g returned; 2,030 Myr-old basalt.

LIFTING OFF THE MOON: THE ROCKET EQUATION

Δv = I_sp g₀ ln(m₀ / m_f) ⇒ m_prop = m_f (e^{Δv / (I_sp g₀)} − 1)

m_f: everything that reaches orbit.

MASS DELIVERED TO ORBIT—

ENGINE SPECIFIC IMPULSE—

Δv TO LUNAR ORBIT—

Illustrative.

CH.07 / 10 — THE FAR SIDE IN A CAPSULE

Chang'e 6: the first rocks from the hidden hemisphere

Chang'e 6 landed in Apollo crater on the far side.

1,935.3 g returned; 2.8-billion-year-old far-side basalt.

CH.08 / 10 — NEXT: THE SOUTH POLE, AND PEOPLE

From robots to a research station

The next phase targets the south pole.

It joins the crewed programme.

CH.09 / 10 — LEGACY: ORBIT, LAND, RETURN

Seventeen years from first orbit to far-side samples

The far side needed a bridge first.

CH.10 / 10 — REFERENCES

RABBITCHANG'E AND THE FAR SIDE OF THE MOON