Sierra Nevada Corporation — Zero Gravity Mass Measurement Device (ZGMMD)¶
Investigated: 2026-04-05 (Session 2) | Updated: 2026-04-07 (Session 72)
Summary¶
Sierra Nevada Corporation's ZGMMD (FO project 71984) achieved TRL9 through parabolic flight testing in 2016–2017. The device measures the mass of 1–100g objects in microgravity using Newton's second law (force + acceleration → mass). NASA ISS Research indicated a need for such a device — no existing ISS instrument could accurately measure low-mass objects (relevant to biological specimens, rodents, plant samples). USASpending confirms $2M in NASA development funding (2014–2017). ISS deployment confirmed: the device has been on-orbit and operational since 2017 as the Sierra Space "Mass Measurement Device (MMD)." Sierra Space lists it in their spaceflight hardware catalog and on satsearch.co as a commercial ISS product. Previous KB versions incorrectly stated deployment was unconfirmed.
Outcome category: TRL9 achieved → ISS deployment confirmed (2017–present) → commercial product (Sierra Space catalog)
FO Project¶
Project 71984 — Zero Gravity Mass Measurement Device (ZGMMD) Parabolic Flight Test¶
- Period: 2016-06-15 to 2017-08-14
- Status: Completed
- TRL: 4 → 9
- Program: FO
- PI: John Wetzel
- Co-investigators: Robert C. Richter, Robert Morrow
- Library item: "International Space Station Transition Report" — general ISS document, not ZGMMD-specific
- Lead org: Sierra Nevada Corporation (ORBITEC division, fully integrated into SNC as of Jan 2, 2017)
Technology Description¶
The ZGMMD provides microgravity mass measurement using Newton's second law: - Known force applied by actuator + measured acceleration → calculated mass - Range: 1 to 100 grams (extended to 2,000g per some SBIR descriptions) - Accuracy: ±0.1g for <20g samples; ±1% for >20g samples - Form factor: designed for ISS Microgravity Sciences Glovebox (MSG) - Target applications: live rodent specimens, plant samples, biological research
Why this matters for ISS: Biological experiments on ISS routinely need to know specimen mass. Without a low-mass measurement capability, researchers must estimate or use Earthside mass with corrections for launch/mission variability.
Development History¶
| Phase | Contract | Amount | Period |
|---|---|---|---|
| SBIR (via SNC/ORBITEC) | see SBIR.gov | — | Pre-2014 |
| NASA development contract | NNX14CA12C | $2.00M | 2014–2017 |
| FO parabolic flight | 71984 | (FO budget) | 2016–2017 |
| NASA follow-on | 80JSC017F0134 | $89.5K | 2017–2018 |
| Parallel work | NNX16CJ57C (ORBITEC) | $300K | 2016–2017 |
The NNX16CJ57C contract ($300K) explicitly requires "a 1–100 gram mass measurement device for use in the microgravity environment of the International Space Station" — awarded to "Orbital Technologies Corporation" (ORBITEC), the SNC division. This confirms ISS target application but not deployment.
ISS Deployment Status¶
Status: CONFIRMED — on-orbit since 2017
Sierra Space (SNC spinoff, 2021) lists the Mass Measurement Device (MMD) in its spaceflight hardware catalog and states it has been "on-orbit and in operation since 2017." The device is also listed on satsearch.co as a commercial product. Two versions of the product sheet exist (Jan 2024, Nov 2024), confirming active marketing.
The ZGMMD parabolic flight test (FO 71984) in 2016–2017 directly preceded the 2017 ISS deployment. The timeline: FO parabolic validation → ISS flight qualification → operational deployment within ~1 year.
CORRECTION (Session 49): Previous KB versions (Sessions 2–31) stated ISS deployment was "unconfirmed" with "LOW confidence." This was wrong. The original Session 2 search missed Sierra Space's product catalog, and subsequent refreshes perpetuated the error. The MMD has been confirmed operational on ISS for 9+ years.
Confidence: CONFIRMED for ISS deployment and ongoing operation
Corporate Context¶
Sierra Nevada Corporation → Sierra Space (spun off 2021, focusing on Dream Chaser cargo spacecraft and commercial space stations). The MMD survived the reorganization and is now a commercially marketed ISS product.
Session 31 note — Dream Chaser status: Sierra Space's Dream Chaser demo-1 flight (Tenacity) delayed to late 2026. In Sep 2025, NASA modified the CRS contract so the demo flight will be a free-flight only (no ISS docking). Future ISS resupply missions are optional. Despite Dream Chaser turbulence, the ISS payloads division (which includes MMD) continues to operate — the Nov 2024 product catalog update confirms active marketing.
Session 49 correction: The Session 31 conclusion that "corporate turbulence makes ZGMMD ISS deployment even less likely" was wrong. The device was already deployed and operating when that assessment was written. This is a case where the KB's prior assessment was directionally backwards — the product was not at risk, it was already a success.
Session 72 update (2026-04-07): No change. MMD continues operating on ISS. Dream Chaser demo-1 remains targeted for late 2026 as a free-flyer only (no ISS docking). USASpending confirms the same 3 contracts ($2.0M + $300K + $89.5K = $2.39M total). No new contracts or ISS experiment references found for MMD specifically.
Confidence Assessment¶
| Claim | Confidence | Evidence |
|---|---|---|
| ZGMMD reached TRL9 in parabolic flights | confirmed | TechPort fields |
| NASA paid $2M for ZGMMD development | confirmed | USASpending NNX14CA12C |
| ZGMMD targeted ISS Glovebox | confirmed | Contract description text |
| MMD deployed and operating on ISS since 2017 | confirmed | Sierra Space product catalog (Jan 2024, Nov 2024), satsearch.co listing |
| MMD is a commercially marketed product | confirmed | Sierra Space ISS Payloads page, product sheets |
Open Threads¶
- ~~Search NTRS for "ZGMMD ISS" deployment report~~ — RESOLVED: ISS deployment confirmed via Sierra Space product catalog
- ~~Did Sierra Space retain the ZGMMD product?~~ — RESOLVED: Yes, marketed as MMD in their spaceflight hardware catalog
- ~~Is ZGMMD now sold as a commercial ISS facility product?~~ — RESOLVED: Yes, listed on satsearch.co
- NEW: What specific ISS experiments have used the MMD since 2017? (Check NASA ISS experiment archives)
- NEW: Has the MMD been used for rodent mass measurement as originally intended, or primarily for plant/sample mass?