Memory Bridge (main): 2026-08-09
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memory/2026-08-09.md
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- Updated: 2026-08-10T06:46:36.823Z
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# 2026-08-09
## Resume point: Rover mesh comms + Bop Bag Antenna deployable (SC Robotics)
Tyler needs to step away to work on a different project tonight (unspecified) — this is the "where I left off" note for picking the mesh/antenna work back up.
**Where the design landed tonight:**
- **Mesh protocol decision**: batman-adv on both bands, but the two radios must NOT be bonded into one `bat0`. Bonding/interface-alternating in batman-adv is link-quality-driven, not traffic-type-aware, so it can't guarantee "controls always here, video always there."
- **900MHz leg**: batman-adv over Wi-Fi HaLow (802.11ah) via the OpenMANET project (Raspberry Pi + Morse Micro HaLow HAT, e.g. Seeed WM1302). Long range, low bandwidth (single-digit Mbps close, ~0.2-0.4 Mbps at 1.5km). Carries control/autonomy commands — small, latency-sensitive, isolated so video traffic can never starve it.
- **2.4GHz leg**: plain batman-adv over standard 802.11s WiFi. Short range, high bandwidth. Carries video.
- Steering plan: bind control socket to the 900 interface, video socket to the 2.4 interface (SO_BINDTODEVICE / ip rule), keep them as two separate subnets/interfaces rather than one merged mesh.
- **Link-health monitoring**: don't build custom heartbeat — batman-adv already exposes this live via netlink. Use `batctl event` (real-time link up/down + TQ changes), `batctl if`, `batctl o`, `batctl tp <mac>`.
- **Selective streaming plan**: video does graceful degradation (step down bitrate/res as 2.4 TQ degrades, drop to periodic low-res stills over 900 as last resort if 2.4 fully drops). Controls on 900 stay unaffected since it's a separate link.
- **Open question, not yet resolved**: does every relay node need both radios (dual-radio everywhere), or just the rover↔base link, with dedicated single-band relay nodes elsewhere? Was about to sketch this in Excalidraw to decide.
- **Mechanical (bop bag antenna mast)**: going expendable — buy pre-made bop bags, cut open, install hardware inside, inflate once via CO2 cartridge + inline regulator (targeting Mars-superpressure fill, well below sea-level cartridge charge). If it needs to come down, break it apart and reinstall hardware in a fresh one. Rejected: rover-mounted pump/reload redeployable system (adds compressor + reseal engineering for a feature likely only needed once) and self-rigidizing resin cure (can't redo antenna tests once cured, so no point).
- **Blocked**: AIAA paper (Cadogan & Scarborough, "Rigidizable Materials for Use in Gossamer Space Inflatable Structures," AIAA 2001-1417) — ResearchGate and AIAA ARC both blocked/paywalled, no full text pulled yet. Not needed now since self-rigidizing was scrapped, but flag if it comes back up.
- **Notion still not authorized this session** — the Mars-pressure/regulated-fill/film-vs-latex writeup was approved to add to the "Bop Bag Antenna" Notion page but hasn't been added yet (blocked on Notion re-auth, same issue as the PO tracker).
**Local files**: `~/workspaces/excalidraws/Robotics/` — `LoRa + manet.excalidraw`, `bop-bag-antenna.excalidraw`, `Chassis Brainstorm.excalidraw`, `PID.excalidraw`, `Electrical Drawing Idea.excalidraw`, `DHT20_practice.excalidraw`. Git repo (`tylervovan/excalidraws`), most recent commits: `asdf`, `more batman`, `batman wifi halow`, `bop bag` — all clean/committed as of tonight.
Notes