Ground Prototype
A quarter-scale vacuum test validates the critical LDR physics at matched Weber number, advancing from TRL 3 to TRL 5 with a single focused campaign.
Quarter-Scale Prototype Design
The key scaling insight: by increasing rotation rate from 2 RPM (flight) to 8 RPM (prototype), the quarter-scale disk matches the flight article's Weber number (We≈58) and rim acceleration (0.045g) exactly. All capture physics transfer directly.
2.5m
Disk radius (25% scale)
8 RPM
Rotation rate (4× flight)
We≈58
Matched to flight article
Flight vs Prototype Scaling
| Parameter | Flight (D3) | Prototype |
|---|---|---|
| Disk radius | 10 m | 2.5 m |
| Rotation rate | 2 RPM | 8 RPM |
| Rim acceleration | 0.045g | 0.045g (matched) |
| Weber number | ≈58 | ≈58 (matched) |
| Nozzles | 27,248 | 1,703 (scaled) |
| Vacuum level | 10&sup4; Torr+ | 10³ Torr |
| Test article mass | N/A | 65 kg |
Bill of Materials
| Category | Cost |
|---|---|
| Mechanical (frame, spars, rim) | $6.5K |
| Nozzle plate (laser-drilled SS, 1,703 nozzles) | $5.0K |
| Fluid system (DC-705, pump, rotary union) | $7.3K |
| Motor & bearing (direct-drive, 8 RPM) | $7.0K |
| Mesh collector (316L SS woven) | $4.5K |
| Instrumentation (IR camera, flow meter, sensors) | $37K |
| Facility rental (3 weeks vacuum chamber) | $30K |
| Travel & consumables | $20K |
| Labor (design, fab, test) | $70K |
| Subtotal | $187K |
| Contingency (20%) | $38K |
| TOTAL | $225K |
4-Phase Test Campaign
Phase 1
Dry Spin (2 days)
RPM sweep 0→8 RPM. Validate structural integrity, vibration <0.5 mm pk-pk, bearing performance.
Phase 2
Atmospheric Spray (3 days)
Nozzle operation, droplet formation characterization. Target: monodisperse droplets, >99% capture in atmosphere.
Phase 3
Vacuum Spray: KEY TEST (1 week)
Full LDR operation in 10⁻³ Torr vacuum. Multiple 1–4 hour runs. Parameter sweeps: RPM (4, 6, 8), pressure (50%, 75%, 100%), duration (15m, 1h, 4h).
Phase 4
Endurance & Off-Nominal (3 days)
8-hour continuous run. Nozzle blockage simulation (10%, 20%, 50% blocked). Emergency stop and recovery procedures.
TRL 5 Gate: Success Criteria
| Criterion | Target | Priority |
|---|---|---|
| Capture efficiency @ We≈58 | >99.9% | MUST |
| Fluid loss in vacuum | <0.01 g/hr | MUST |
| Droplet size uniformity (CV) | <15% | MUST |
| Sustained operation | >1 hour | MUST |
| Drainage to steady state | <60 sec | SHOULD |
| IR thermal vs model agreement | ±15% | SHOULD |
| 8-hour endurance | Complete | NICE |
| 20% nozzle loss tolerance | <5% perf drop | NICE |
Facility Options
| Facility | Cost/Week | Pros | Cons |
|---|---|---|---|
| NASA GRC VF-13 | $10–30K | Credibility, infrastructure | Booking availability |
| AFRL Kirtland | CRADA | DoD relationship | Limited availability |
| University | $5–15K | Low cost, publications | Smaller chambers |
| Commercial TVAC | $15–50K | Professional support | Highest cost |
6-Month Timeline
Mo 1–2
Design & procurement: Detailed design, long-lead orders (laser-drilled nozzles 8–10 week lead time)
Mo 3–4
Fabrication & assembly: Machine frame, integrate fluid loop, bench testing at ambient
Mo 5
Vacuum testing: 3 weeks on-site at facility. All 4 test phases. Data collection.
Mo 6
Analysis & reporting: Data reduction, final report, investor video, SBIR proposal submission
Investment Leverage
$225K
Ground prototype investment
60–100×
Return leverage on first hardware dollar
Successful TRL 5 demonstration unlocks SBIR Phase II ($1.5M), OTA ($10–15M), and Series A ($15–20M), a total of $12–20M in follow-on funding.