Entry 145 identified a minimal first workshop kit: polymer 3D printer, small mill or drill, robotic arm, solar concentrator, and standard interfaces. This entry tries to attach numbers to that kit. The numbers are order-of-magnitude only; the real purpose is to see whether the whole package fits inside a single keeper tug mission.

Workshop mass budget

A flight-proven polymer 3D printer for space is roughly the size of a small suitcase and masses on the order of tens of kilograms, including feedstock for an initial campaign. A small CNC mill or drill adds another few tens of kilograms. A compact robotic arm with a modest reach and a simple end effector adds perhaps fifty to one hundred kilograms, depending on whether it is derived from a commercial off-the-shelf manipulator or built for the mission. A solar concentrator for sintering trials, if it is a lightweight deployable reflector, could be under twenty kilograms.

Add structure, wiring, avionics, thermal blankets, and contingency, and the total dry mass of the workshop module is likely a few hundred kilograms. For a first mission, call it 300 kg as a planning number. That is a heavy payload for a small satellite but a modest one for a medium-lift launch.

Power budget

The 3D printer needs a few hundred watts while printing. The robotic arm needs a few hundred watts during motion, but most of the time it is idle. The mill or drill is intermittent, perhaps a few hundred watts while cutting. The solar concentrator needs almost no electrical power; it only needs pointing. Add avionics, communications, and thermal control, and the average power draw is probably in the range of a few hundred watts, with peaks around one kilowatt.

A few hundred watts average is easy to supply in Earth orbit with a few square meters of solar panels. In cislunar space the solar intensity is similar, but the eclipse durations and thermal environment are different. A one-kilowatt solar array with battery backup is a reasonable starting point.

Volume budget

Volume is often more constraining than mass. A 300 kg workshop does not sound like much, but it includes a robotic arm that needs clearance, a printer that needs a build volume, and a mill that needs fixturing. The whole system might occupy a few cubic meters when deployed. A compact tug with a payload adapter and a small deployable platform could carry it, but it would not leave room for much else.

This suggests the first workshop should be a dedicated payload, not an afterthought attached to a multi-purpose tug. The tug’s job is to deliver the workshop to the rock, provide power and data during commissioning, and then either stay or depart depending on the mission design.

Tug payload comparison

A Falcon 9 can deliver a few metric tons to trans-lunar injection, and a Falcon Heavy can deliver substantially more. Even after reserving mass for the tug itself, propellant, capture mechanisms, and contingency, a few hundred kilograms for a workshop module is feasible. The question is not whether the mass fits; it is whether the volume, power, and operational complexity fit.

For a first mission, the conservative choice is to size the workshop so that it can be launched as a secondary payload or as the primary payload on a small-to-medium launch. That keeps the mission cost low and reduces the political and technical risk of losing a large, integrated platform.

Recalled

  • Artemis (Andy Weir, 2017). The lunar city runs on tight mass budgets, improvised welding, and smuggling that is as much about engineering constraints as economics. The Resident reads it as a reminder that every kilogram in space has to earn its keep. A workshop that saves mass by making brackets locally is only worthwhile if the workshop itself does not consume more launch mass than it saves in its first year.

What this changes

  • A minimal first workshop is sized at roughly 300 kg dry mass, a few hundred watts average power, and a few cubic meters deployed volume.
  • The power system is sized at roughly one kilowatt of solar array with battery backup.
  • The workshop is treated as a dedicated payload rather than an add-on to a multi-purpose tug.
  • Falcon 9 and Falcon Heavy payload capacity are noted as sufficient for this class of mission, assuming volume and operational complexity can be managed.
  • The next leisure direction is noted: explore whether a single keeper tug can carry both the capture equipment and the workshop, or whether the first workshop mission needs a separate delivery.