MACHINIST'S MATE (AUXILIARY) (MMA)

OVERVIEW

Machinist's Mate (Auxiliary) — MMA — is the submarine-auxiliary mechanic. MMAs operate and maintain the high-pressure air systems, hydraulic systems, refrigeration and air-conditioning, atmosphere-control equipment (CO2 scrubbers, oxygen generators, hydrogen burners), trim and drain systems, and the diesel emergency generator on every U.S. Navy submarine.

The submarine community is an all-volunteer force that operates the Navy's nuclear-powered fast-attack, guided-missile, and ballistic-missile submarines. Sailors must qualify in submarines (earning the Silver or Gold Dolphins) and operate under unique deployment cycles, watchbills, and the demanding Submarine Force standards established by Admiral Hyman G. Rickover.

A-school for the rating runs ~14 weeks at Naval Submarine School, Groton, CT, where Sailors complete the technical foundation needed to report to their first fleet command. Entry requires the ASVAB line score VE+AR+MK+AS=210 and an enlistment obligation of 6–6 years. MMAs advance through the standard enlisted paygrade structure (E-1 through E-9), competing in the Navy-Wide Advancement Examination (NWAE) at E-4 through E-6 and via the Selection Board at E-7 through E-9. Senior MMAs typically serve as Leading Petty Officer (LPO), Work Center Supervisor, Leading Chief Petty Officer (LCPO), or Command Master Chief (CMC), and may pursue Limited Duty Officer (LDO), Chief Warrant Officer (CWO), or commissioning programs such as STA-21, MECP, or OCS.

Across the active force, MMA Sailors are essential to the Navy's mission readiness, and the rating remains an in-demand career field with strong reenlistment bonuses (SRB), advancement opportunities, and pathways into Navy Reserve, civilian DoD, and industry careers after service.

WHAT MMAs DO

MMAs operate and maintain submarine atmosphere-control equipment (CO2 scrubbers, electrolytic oxygen generators, CO/H2 burners), high-pressure air, hydraulics, refrigeration, sanitary systems, and the emergency diesel. They stand the Auxiliary Electrician Forward / Engineroom Lower Level watches.

RESPONSIBILITIES

• MMAs operate and maintain submarine atmosphere-control equipment (CO2 scrubbers, electrolytic oxygen generators, CO/H2 burners), high-pressure air, hydraulics, refrigeration, sanitary systems, and the emergency diesel. They stand the Auxiliary Electrician Forward / Engineroom Lower Level watches.
• Stand watches and qualify on the rating's Personnel Qualification Standards (PQS), maintain training jackets, and mentor junior MMAs as required by the chain of command.
• Lead the MMA work center as Leading Petty Officer or Work Center Supervisor — managing maintenance documentation in 3M/MFOM, parts ordering, and personnel qualifications.
• Support general military training (GMT), damage control, force protection, and watch-bill assignments common to every Sailor regardless of rating.

HISTORY

Machinist's Mate (Auxiliary) is the modern designator for the submarine non-nuclear MM track, formalized when the submarine MM ratings were aligned to MMA, MMW, and MMN sub-specialties.

The submarine rating lineage traces to the commissioning of USS Holland in 1900 and the establishment of the Submarine Force the same year. Modern submarine enlisted ratings were redefined under Admiral Hyman G. Rickover in the 1950s as the Navy transitioned from diesel-electric to nuclear propulsion with USS Nautilus (SSN-571).

Today the Machinist's Mate (Auxiliary) (MMA) rating is overseen by the Enlisted Community Management (ECM) office at My Navy HR and the Center for Personal and Professional Development. Modern MMAs benefit from the Sailor 2025 personnel-system reforms, the Ready Relevant Learning (RRL) training continuum, and credentialing through the Navy COOL program — turning rating qualifications into industry-recognized certifications and licenses.

The rating's structure, training pipeline, and operational employment continue to evolve alongside the Navy's transition to Distributed Maritime Operations (DMO), Project Overmatch, and the Force Design 2045 fleet architecture, ensuring MMAs remain central to the warfighting mission.

TRAINING PIPELINE

1. 1. Recruit Training (Boot Camp)~10 weeks
   Naval Station Great Lakes, IL
   Initial entry training for all U.S. Navy enlisted Sailors at the Navy's only boot camp.
2. 2. Machinist's Mate (Auxiliary) A-School~14 weeks
   Naval Submarine School, Groton, CT
   Submarine pipeline rating training (includes Basic Enlisted Submarine School)
3. 3. Fleet / Operational TourFirst sea or operational tour
   Virginia (SSN-774) class submarines
   On-the-job training and qualifications in the MMA rating with a fleet unit.

TYPICAL CAREER PATH

1. E-1/E-3
   Apprentice MMA
   A-school in the submarine pipeline; first tour with a fleet unit.
2. E-4/E-6
   Petty Officer MMA
   Lead a Machinist's Mate (Auxiliary) work-center, qualify in core watchstations and platform-specific tasks.
3. E-7+
   Chief Machinist's Mate (Auxiliary)
   Senior enlisted leader of the rating in the command; instructor, detailer, or department leading chief assignments.

TYPICAL PLATFORMS & UNITS

• Virginia (SSN-774) class submarines
• Los Angeles (SSN-688) class submarines
• Ohio (SSBN/SSGN-726) class submarines

EXAMPLE NECs

• MMA-4231 Submarine Auxiliary Mechanic

RELATED RATINGS

• MM · General Surface & Combat
  Machinist's Mate
• MMW · Submarine Force
  Machinist's Mate (Weapons)
• EN · General Surface & Combat
  Engineman

RELATED BASES

• Navy Base · CT
  Naval Submarine Base New London
• Navy Base · GA
  Naval Submarine Base Kings Bay
• Navy Base · WA
  Naval Base Kitsap

FREQUENTLY ASKED QUESTIONS

SOURCES

• Navy Machinist's Mate (Auxiliary) (navy.com)
• My Navy HR — Enlisted Community Management
• Navy COOL — Rating Detail