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The build plan·Chapter 7.2

The first 90 days

Ninety days is the measurement wave, the PDR and most of the architecture wave. The sequence below is the problem register’s dependency order read forwards, so it is a work sequence rather than a schedule with names attached; ownership belongs to the team. Four gates sit inside the window, and four early warnings mark a season that is already slipping.

90DaysFrom 2026-10-26 to the end of January 20272026-2027
4Gates inside the windowMass, task geometry, link and payload, safety2026-2027
5Week of the PDRThe register counts weeks from 0, so this is week 6 elsewhere2026-12-02
6Load-bearing rows startedSix of the thirteen high-dependency rows are measurements2026-2027

Key takeaways

  • The first four weeks replace the numbers the rulebook does not publish. They are bench and field measurements, and every later wave spends their results.
  • The PDR falls five weeks into the season, at 2026-12-02, so the measurements have to start on day one rather than after the team is organised.
  • Four gates decide whether the rest of the register is executable: a weighed mass allocation, a task panel with measured force curves, a measured link with terrain in the way, and a payload pair with a proven kill chain.
  • If those four are false at the end of January, no amount of design work recovers the season. Each has a fallback, and the fallback is accepted in writing.

The sequence

The register numbers its rows from week 0, which is why its week 5 is the sixth numbered week in the risk calendar later in this part. The dates are the same dates. The PDR is due 2026-12-02 S-URC27-RULES §3.a.ii, and the SAR is due 2027-03-05 S-URC27-RULES §3.a.iii, forty-one days after the window closes.

Weeks Dates What gets done Register rows What it decides
0–1 2026-10-26 to 11-08 Weigh every part; cut the timber 1.2 m gauge; start the judge-like task panel; breadboard the kill chain; write and send the question letter W0-01, W0-02, W0-17, and the twenty questions The mass frame and the task geometry become measured facts, and the questions start their clock
2–3 11-09 to 11-22 Force and torque campaign on the panel; keyboard and hammer trials; soil and drilling rig; traction and step rigs; the 1 km link test; RTK survey-in trial; tag range sweep; enclosure lamp test W0-03 to W0-11, W0-13 to W0-15 Every unpublished force and range in the arm, mobility and communications designs is replaced
4 11-23 to 11-29 Close the measurements; fix the arm mass class; fix the stow concept; choose the assay pair in working form; choose the E-stop and distribution architecture; time the C2 station W1-01, W1-06, W1-11, W1-13, W0-19, W0-20 The four PDR claims: mass, stow, payload and safety
5 11-30 to 12-06 PDR submitted on 2026-12-02; freeze the numbers that tooling depends on W1-26 and the PDR gate set The design is credible enough to keep building
6–9 12-07 to 2027-01-03 Mobility and drivetrain: four or six wheels, wheel diameter, torque, voltage, chassis; arm architecture and backlash class; power architecture W1-02 to W1-05, W1-07 to W1-09, W1-12, W1-21 Tooling can start and long-lead parts can be ordered against a frozen number
10–13 2027-01-04 to the end of January Communications, compute and mast; autonomy stack; GNSS base strategy; modularity plan; astronaut ladder; C2 architecture; the first interface documents W1-14 to W1-20, W1-22 to W1-25, W2-01 to W2-05 The detailed-design wave begins with numbers already frozen rather than with assumptions

The same window as a dated calendar with one decision per week is on the 13-week plan page. This page gives the order of the work; that page gives the decision dates and the owner of each row.

The four gates inside 90 days

  1. Mass. A weighed allocation at 48.5 kg or less with growth allowed for, and a concept that passes the cube gauge. The row is W0-01 and it unlocks nine later problems.
  2. Task geometry. A task panel with measured force curves for all nine Equipment sub-tasks, built before any arm hardware is bought. The row is W0-02 and W0-03.
  3. The link. A link measured at 1 km with terrain in the way, RTK accuracy measured, and tag ranges measured in full sun. The rows are W0-11, W0-13 and W0-14.
  4. Payload and safety. An assay pair chosen with bench data and a written justification, and an E-stop circuit proven on the bench with a current probe. The rows are W0-08, W1-11 and W0-17.

A gate is not a meeting. Each is a number with an artefact behind it, and each is closed by a document that the review package can later quote. These four are technical gates; the four management gates G1 to G4, which track ownership and decision dates, are on the 13-week plan page.

Four early warnings

These are the observable signs that the schedule is already behind, and each has the same remedy: run the measurement, or accept the fallback in writing and move on.

  • The task panel is not built by the end of week 2. Every arm and end-effector decision is now being taken on assumed forces, and the arm’s open questions are all open at once.
  • There is no measured link by the end of week 3. The radio, the camera count and the mast are being chosen on a spreadsheet model, and the communications package becomes a discovery exercise in April.
  • The assay pair is not chosen by the PDR. The review video cannot show a mandatory capability, and the science payload is re-architected after the review, which is the most disruptive change this project can make.
  • The question letter has no answer by the end of November. Three of the four December decisions are then taken on the fallback, which is the conservative choice and may cost capability.

Four commitments the 90 days must not break

  • The arm is not bought before the mass class is fixed, because the arm class consumes the drivetrain margin and that coupling is invisible until the motor class changes.
  • The chassis is not built before the wheel diameter is frozen, because that one number reopens seven to nine interfaces.
  • Radios are not chosen before the link test, and cameras are not chosen before the tag sweep. Both are measurements, and both are cheap in week 3 and expensive in April.
  • The question letter is not deferred. Answers take weeks, and three of the four December decisions depend on them.

What the window produces

By the end of January the team holds a weighed mass frame, a task panel with force curves, soil and traction data, a measured link and tag range, a lamp-tested enclosure, a proven kill chain, a measured pack sag, a timed station, two analogue sites and a recording discipline that makes every later measurement usable as review evidence. That list is the deliverable, and it is worth more than a design that is one revision further along.

Further reading

Sources for this page

  1. S-URC27-RULESUniversity Rover Challenge 2027 – Requirements and GuidelinesThe Mars Society / URC.Original Archived copy