MIL-S-901

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MIL-S-901D is a military specification for high‑impact shock that shipboard equipment must withstand. It was published on March 17, 1989. The standard covers shipboard machinery, equipment, systems, and structures (but does not include submarine pressure hull penetrations). Its purpose is to verify that installations can survive the shock from weapons used in wartime.

Grades
- Grade A: items essential to safety and the ship’s combat capability.
- Grade B: items not essential to safety or combat capability, but that could become hazardous to personnel, Grade A items, or the ship if exposed to shock.
- Grade C: sometimes referenced in documents, but it has no official standing in the standard.

Testing overview
- Tests are conducted to verify shock performance. Testing is done on a barge (floating platform) or a large floating platform, using explosions to generate shock.
- A hammer test may be used to pre‑qualify an item, but final compliance with MIL-S-901D is demonstrated on a barge.
- Because test methods and reporting vary, buyers should verify (i) the test method claimed, (ii) which parameter limits were actually tested, and (iii) whether the testing was internal or by an independent facility.

Barge test specifics
- Standard floating platform: 60 pounds (27 kg) HBX‑1 explosive placed 24 feet (7.3 m) underwater at four positions: first shot on the fore‑aft axis 40 feet (12 m) from the barge; shots 2–4 athwart ship at 30, 25, and 20 feet (9.1, 7.6, 6.1 m) from the near side of the platform.
- Large floating platform: 300 pounds (140 kg) HBX‑1 placed 20 feet (6.1 m) underwater with four shots at 110, 80, 65, and 50 feet (34, 24, 20, 15 m) from the barge; first shot fore‑aft, others athwart ship.

Other notes
- The standard also specifies a hammer pre‑qualification approach, but the official MIL‑S‑901D qualification is performed on the barge.
- Related point: another standard, MIL‑DTL‑17060G(SH), defines shock testing for electric motors by weight class. Lightweight motors (up to 250 lb) get nine shocks while running at no load and nine shocks while stationary. Medium weight motors (up to 6,000 lb) are tested with the motor running or stationary. Motors over 6,000 lb are tested on a floating platform or barge.