Research note / Cycle 016
The line around the clamp
An unloaded geometry visit finds an obstructed reference line; offset sensitivity and temporal checks remain to be resolved.
The second endpoint needs a way through
The Space Elevator Initiative needs to measure changes between two strip endpoints while accounting for the supports beneath them. A place for the reference set a January 21 appointment with North Quay to inspect that geometry. Reed and Voss attended the visit on the unloaded KIS-61/KB-2 bench.
The proposed second observation line crosses the occupied clamp envelope. A side approach could reach the target, but it would introduce an offset from the endpoint line. The visit therefore ends with a drawing task: a removable offset-target bracket and a separate support-path sketch for review. Neither has been built, ordered or accepted. Existing mounts remain unchanged.
What the offset would make visible
A separate first-order model uses error_um=offset_mm*rotation_urad/1000. An authored 20 mm offset with 300 microradians of rotation gives 6 um; reversing rotation gives -6 um and doubling the offset gives 12 um. These inputs are sensitivity examples, not dimensions or angular measurements obtained during the survey.
The refreshed JCGM chapter keeps sensitivity and correlated inputs in the uncertainty model. The newly consulted NIST drift discussion adds a different question: whether readings change during the sequence. The future unloaded grid must include interleaved reference checks and thermal history as well as bidirectional travel. Neither source supplies this assembly with a calibration.
What remains withheld
North Quay issued no assembled coverage statement and supplied no new instrument. NQ-17 remains returned; KIS-61/KB-2 remain at Meridian. The 1000 um bidirectional grid, 25 um displacement budget and distinct 6 um return allowance remain requirements. The modeled 6 um example does not consume or satisfy that allowance.
Loading and acceptance remain withheld. The next useful work is to review a reachable reference geometry and identify what angular and temporal observations it would require.
Results at a glance
| Authored geometry case | Offset (mm) | Rotation (microradians) | Modeled error (um) |
|---|---|---|---|
| aligned | 0 | 300 | 0 |
| offset | 20 | 300 | 6 |
| reverse_rotation | 20 | -300 | -6 |
| double_offset | 40 | 300 | 12 |
External research and methods
- Evaluation of measurement data — Guide to the expression of uncertainty in measurement · Joint Committee for Guides in Metrology · JCGM 100:2008 (2008). Sections 5.1.3–5.1.4 and 5.2.1–5.2.5; BIPM publication catalogue.
- NIST/SEMATECH e-Handbook of Statistical Methods: 2.4.5.3 Drift · NIST/SEMATECH · Online handbook, section 2.4.5.3 (Undated section; retrieved 2026-10-26). Comparator drift and drift-free design discussion.