Navy Machinist’s Mates, Non-Nuclear, Submarine Auxiliary (MMA): Definitive Guide

Some people call the reactor the heart of a submarine. Without A-Gang, the crew still cannot operate for long.

As a Machinist’s Mate Auxiliary (MMA), you keep the submarine running in the most basic ways. You help make the air breathable. You help keep water available for drinking and daily use. You also support systems that make the boat livable.

Your work touches major equipment across the submarine. That includes oxygen systems, water systems, heating, hydraulics, high-pressure air, plus diesel engines. If a system moves, pumps, or helps power the boat, you may be the one working on it. While others focus on the mission, you help keep the boat operating.

ENLISTMENT BONUS: Future Navy MMAs are currently eligible to receive up to $10K in cash bonus just for signing up.

Job Description

Machinist’s Mates, Non-Nuclear, Submarine Auxiliary (MMA) are enlisted Sailors who operate, maintain, and repair many systems on submarines. Their work covers damage control gear, internal combustion diesel engines, hydraulic systems, atmosphere control equipment, refrigeration systems, compressed air and gas systems, water systems, plus sanitary and plumbing systems.

MMAs help keep submarines livable and ready to operate. If oxygen systems fail, the crew cannot stay underway. If drinking water is not available, operations cannot continue. A-Gang keeps critical systems working so the submarine can do its job.

Where They Work

• Mostly on submarines, U.S. and international waters.
• Occasional shore duty, but the job is mostly at sea.
• Work in auxiliary spaces, often with minimal supervision.

Key Responsibilities

• Generate and store oxygen. No air, no crew.
• Remove carbon dioxide, carbon monoxide, and hydrocarbons from breathable air.
• Maintain and repair emergency diesel engines, watertight doors, hatches, masts, and antenna hoists.
• Fix, replace, and inspect onboard equipment – valves, pumps, filters, compressors, hydraulic and pneumatic systems.
• Operate and repair refrigeration units and water desalination plants.
• Maintain air conditioning and galley equipment.
• Log and analyze machinery records and reports.

MMA is a hands-on, physically demanding role. You work in tight spaces, with heavy machinery, under pressure. If it breaks, you fix it. If it fails, the whole sub feels it.

Different Roles in MMA

Auxiliary Equipment Manager

Keeps everything running, makes sure the right people are doing the right work.

• In charge of hydraulic power plants, diesel engines, atmosphere control, sanitation systems.
• Manages oxygen generation, compressed gas systems, submarine salvage equipment.
• Trains and supervises the crew keeping things operational.

Auxiliary Equipment Operator

The one turning the wrenches, running the systems, making sure nothing breaks.

• Operates diesel engines, firefighting systems, emergency dewatering, air conditioning, and more.
• Keeps water, air, and power systems functioning.
• Knows electrical safety, steam propulsion, hydraulic power plants.
• Fixes leaks, replaces valves, fabricates parts, whatever needs doing.

Auxiliary Equipment Technician

If something’s broken, they figure it out and fix it.

• Maintains hydraulic power plants, oxygen generators, freshwater systems.
• Oversees system operations, making sure everything is working as it should.
• Keeps maintenance records, tracks repairs, logs test results.
• Diagnoses and repairs failures before they turn into bigger problems.

Everyone in A-Gang has a job. If systems fail, there’s no backup crew—just them.

Rank Structure

Salary and Benefits

Salary for the First 6 Years

Monthly pay for Navy enlisted Sailors (E-1 to E-6) in the first six years is laid out in the January 2026 Active Duty Pay chart:

Extra Pays and Allowances

• Housing allowance (BAH): A tax-free allowance when you live off base. Rates depend on pay grade, location, and dependency status.
• Food allowance (BAS): Enlisted Sailors receive $476.95 per month in 2026. See the BAS rates.
• Career Sea Pay: Extra monthly pay for qualifying sea duty. Amounts depend on pay grade and sea time. See the Career Sea Pay table.
• Submarine Duty Incentive Pay: Monthly submarine pay for qualified Sailors assigned to submarine duty. Amounts depend on pay grade and years of service. See the submarine pay table.
• Bonuses and incentives: The Navy may offer enlistment, skill, or reenlistment bonuses for certain training pipelines and manning needs.

Benefits

• Healthcare: Medical and dental care through TRICARE for the member, with options for dependents.
• Leave: 30 days of paid leave each year, plus federal holidays when operationally possible.
• Education: Tuition Assistance and GI Bill benefits for qualifying service.
• Retirement: Blended Retirement System (BRS) with Thrift Savings Plan (TSP) contributions when eligible, plus a pension after 20 years of service.
• Other benefits: Life insurance, family support programs, and VA benefits after separation, based on eligibility.

Training and Career Opportunities

Boot Camp & Technical Training

• Recruit Training Command Great Lakes (Boot Camp).
• Basic Enlisted Submarine School – Groton, CT (9 weeks).
• Learn basic submarine systems, operations, and safety.

Specialized MMA Training

• Machinist’s Mate “A” School – Groton, CT (9 weeks).
• Covers mechanical theory, safety, piping systems, valves, pumps, tools, and watchstanding.
• Hands-on training in mechanical systems and maintenance procedures.
• Machinist’s Mate “C” School – Groton, CT, King’s Bay, GA, or Bangor, WA (7 weeks).
• Advanced technical training for auxiliary systems operators.
• Focuses on detailed equipment maintenance, troubleshooting, and operational procedures.

First Assignments

• MMAs typically serve on submarines but may also be assigned to naval repair stations in the U.S. or overseas.
• Shore duty may include instructor roles, recruiting duty, or intermediate maintenance activities (SIMAs).

Advanced Training & Career Progression

• Leadership and specialized technical training available throughout a career.
• Opportunities for Officer roles with further education and qualifications.

Post-Service Opportunities

• Civilian careers in power plant operations, industrial machinery, mechanical systems maintenance, and engineering support.
• Directly transferable skills to high-demand industries.

Career Balance

• MMAs spend about 70% of their time at sea and 30% on shore duty.
• Submarine pay ranges from $75 to $600 per month, depending on experience and rank.

Qualifications and Eligibility

Basic Requirements

• Must be a U.S. citizen and eligible for a security clearance.
• High school diploma or GED required.
• Must volunteer for submarine duty.

ASVAB Score Requirements

• VE + AR + MK + EI = 207 or
• AR + GS + MC + EI = 207

Skills & Personal Traits

• Strong math skills – Needed for calculations and technical work.
• Good speaking ability – Clear communication is key in tight spaces.
• Attention to detail – Record-keeping and system monitoring require precision.
• Mechanical aptitude – Must be comfortable working with tools, machinery, and complex mechanical systems.
• Good manual dexterity – Many repairs require fine motor skills.
• Physical stamina – The job can be physically demanding, hot, noisy, and repetitive.
• Team player – You work in close quarters—getting along is non-negotiable.

The enlistment qualification requirements above are current as of Fiscal Year 2026, per the Navy Personnel Command.

More Information

If you wish to learn more about becoming a Machinist’s Mate Auxiliary (MMA), contact your local Navy Enlisted Recruiter. They will provide you with more detailed information you’re unlikely to find online.

You may also be interested in the following related Navy Enlisted jobs:

• Logistics Specialist Submarines (LSS)
• Missile Technicians (MT)