1. Why put numbers on it now
Andy Weir’s The Martian is essentially a long celebration of back-of-the-envelope calculations. Mark Watney survives because he keeps estimating: how much food, how much power, how far, how fast. The numbers are rough, but the act of estimating forces honesty. A mission that has not been estimated is a mission that is still fantasy.
So here is an honest envelope for the keeper’s first spent-stage demonstration. The numbers are wrong in detail, but they are right enough to show whether the idea is in the right order of magnitude.
2. Mass budget
| Subsystem | Mass estimate |
|---|---|
| Structure and harness | 15 kg |
| Power: solar panels, battery, EPS | 12 kg |
| Avionics: flight computer, IMU, GPS, comms | 8 kg |
| Navigation sensors: camera, lidar | 5 kg |
| Propulsion: cold gas or small chemical | 10 kg |
| Capture interface: gripper, magnetic pad, or harpoon | 8 kg |
| Margin and integration | 12 kg |
| Total dry mass | ~70 kg |
Add propellant and the wet mass comes to roughly 90 kg. That fits comfortably inside a 100-kg class microsatellite or a large cubesat deployer.
3. Cost estimate
| Item | Cost estimate |
|---|---|
| Launch as rideshare to LEO | $1–3 M |
| Satellite bus and components | $2–4 M |
| Navigation and capture payload | $1–2 M |
| Ground software and operations | $1 M |
| Integration, test, and launch campaign | $1–2 M |
| Contingency | $1 M |
| Total | ~$7–13 M |
This is a fraction of a traditional government science mission and an order of magnitude below active debris removal demonstrations like ClearSpace-1. It is also more than a university cubesat. The right home for it is probably a small commercial program or a focused technology demonstration contract.
4. Timeline
- Months 0–6: requirements, trajectory selection, and preliminary design.
- Months 6–12: bus procurement and payload development.
- Months 12–18: integration, environmental test, and launch booking.
- Months 18–24: launch, checkout, and approach campaign.
Two years from contract to contact is aggressive but not absurd for a small, single-purpose spacecraft. The long pole is usually launch availability, not hardware.
5. The biggest uncertainty
The largest unknown is not the spacecraft. It is the target. A spent stage’s tumble state, surface condition, and exact center of mass are usually poorly known. The mission might need a reconnaissance phase lasting weeks before any contact attempt. That phase consumes propellant and operations time, and it is not optional.
What this changes
- The first keeper mission is roughly a $10M, 70-kg, two-year effort.
- This puts it in the range of a technology demonstration, not a flagship program.
- The real schedule risk is target characterization, not spacecraft build.
- The next leisure entry can explore who would pay for such a mission and what they would get in return.