diff --git a/CHANGELOG.md b/CHANGELOG.md
index 21544fa..7c8fb35 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Changelog
 
+## September 8, 2026
+
+Launch payloads with missing records now say PAYLOAD DATA UNAVAILABLE. Missing names use Unnamed payload; absent or invalid mass stays unknown instead of appearing as 0 KG.
+
 This changelog records public product changes. For the authoritative description
 of current runtime behavior, see [`docs/CURRENT-STATE.md`](docs/CURRENT-STATE.md).
 
diff --git a/docs/CURRENT-STATE.md b/docs/CURRENT-STATE.md
index 1f4d861..a14cce4 100644
--- a/docs/CURRENT-STATE.md
+++ b/docs/CURRENT-STATE.md
@@ -1,5 +1,9 @@
 # God's Eye View Current State
 
+## September 8, 2026
+
+Launch payloads with missing records now say PAYLOAD DATA UNAVAILABLE. Missing names use Unnamed payload; absent or invalid mass stays unknown instead of appearing as 0 KG.
+
 Updated: August 24, 2026
 
 ## Installations and map-source guidance
diff --git a/src/data/rocketLaunches.js b/src/data/rocketLaunches.js
index bd9bf79..e8fda9b 100644
--- a/src/data/rocketLaunches.js
+++ b/src/data/rocketLaunches.js
@@ -2106,13 +2106,15 @@ function normalizePayloadFlights(launch) {
     const payload = flight.payload || flight;
     return {
       id: String(flight.id || payload.id || `payload-${index}`),
-      name: payload.name || flight.name || 'Undisclosed payload',
+      name: payload.name || flight.name || 'Unnamed payload',
       type: payload.type?.name || flight.type?.name || null,
       manufacturer: payload.manufacturer?.name || null,
       operator: payload.operator?.name || null,
       destination: flight.destination || payload.destination || null,
       amount: Number.isFinite(Number(flight.amount)) ? Number(flight.amount) : 1,
-      massKg: Number.isFinite(Number(payload.mass)) ? Number(payload.mass) : null,
+      massKg: (typeof payload.mass === 'number' || (typeof payload.mass === 'string' && payload.mass.trim() !== ''))
+        && Number.isFinite(Number(payload.mass)) && Number(payload.mass) >= 0
+        ? Number(payload.mass) : null,
     };
   });
 }
@@ -2288,7 +2290,7 @@ function renderMissionPanel() {
   _missionPanel.querySelector('[data-mission-payloads]').innerHTML = missionTableRows(
     payloadRows,
     3,
-    'CLASSIFIED / MULTI-PAYLOAD',
+    'PAYLOAD DATA UNAVAILABLE',
   );
   const stageRows = launch.recoveryStages.map((stage) => {
     const endpoint = stage.endpoint;
diff --git a/src/data/rocketLaunches.test.mjs b/src/data/rocketLaunches.test.mjs
index dd1ae4c..27d29ff 100644
--- a/src/data/rocketLaunches.test.mjs
+++ b/src/data/rocketLaunches.test.mjs
@@ -1253,3 +1253,16 @@ test('disable reports a semantic failure while restoring the satellites dependen
     /could not restore the satellites layer/,
   );
 });
+
+
+test('missing payload details stay unknown without inventing mass or classification', () => {
+  for (const [mass, expected] of [[null, null], [undefined, null], ['', null], ['  ', null],
+    [false, null], [-1, null], ['invalid', null], [0, 0], ['125', 125]]) {
+    const [launch] = normalizeRocketLaunches([{ id: 'mass', pad: { latitude: 1, longitude: 2 }, net: '2026-07-20T10:00:00Z',
+      payloads: [{ mass }] }], NOW);
+    assert.equal(launch.payloads[0].massKg, expected);
+    assert.equal(launch.payloads[0].name, 'Unnamed payload');
+  }
+  const [launch] = normalizeRocketLaunches([{ id: 'missing', pad: { latitude: 1, longitude: 2 }, net: '2026-07-20T10:00:00Z' }], NOW);
+  assert.deepEqual(launch.payloads, []);
+});