physics

SUBSAFE

SUBSAFE is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand SUBSAFE rather than just read about it. In short: The Submarine Safety Program (SUBSAFE) is a quality assurance program of the United States Navy designed to maintain the safety of its submarine fleet, specifically, to provide maximum reasonable assurance that submarine hulls will stay watertight, and that they can recover from unanticipated flooding. SUBSAFE covers all systems exposed to sea pressure or critical to flooding recovery.

Key takeaways

SUBSAFE belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect SUBSAFE to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of SUBSAFE from memory before moving on to harder problems.

Reference excerpt

The Submarine Safety Program (SUBSAFE) is a quality assurance program of the United States Navy designed to maintain the safety of its submarine fleet, specifically, to provide maximum reasonable assurance that submarine hulls will stay watertight, and that they can recover from unanticipated flooding. SUBSAFE covers all systems exposed to sea pressure or critical to flooding recovery. All work done and all materials used on those systems are tightly controlled to ensure the material used in their assembly as well as the methods of assembly, maintenance, and testing are correct. They require certification with traceable quality evidence which track the item from the point of manufacture (including all records of the creation of the product, i.e. source materials as well as smelting and hardening process for metals) to the point of installation within a SUBSAFE boundary. These measures increase the cost of submarine construction and maintenance. SUBSAFE addresses only flooding; mission assurance is not a concern, simply a side benefit. Other safety programs and organizations regulate such things as fire safety, weapons systems safety, and nuclear reactor systems safety. From 1915 to 1963, the United States Navy lost 16 submarines to non-combat-related causes. Since SUBSAFE began in 1963, only one submarine, the non-SUBSAFE-certified USS Scorpion (SSN-589), has been lost.

History On 10 April 1963, while on a deep test dive about 200 miles off the northeast coast of the United States, USS Thresher (SSN-593) was lost with all hands. The loss of the lead ship of a new, fast, quiet, deep-diving class of submarines led the Navy to re-evaluate the methods used to build its submarines. A "Thresher Design Appraisal Board" determined that, although the basic design of the Thresher class was sound, measures should be taken to improve the condition of the hull and the ability of submarines to control and recover from flooding casualties. It included addressing the following issues on Thresher:

Some silver-brazed joints could have been substandard. One or more of these joints is believed to have failed, resulting in flooding in the engine room. There is however, no specific evidence of flooding and photographs of the hull suggest that the machinery spaces did not flood (no equalization). The crew was unable to access vital equipment to stop the flooding. Saltwater spray on electrical components caused short circuits, reactor shutdown, and loss of propulsion power. The main ballast tank blow system failed to operate properly at test depth. Various restrictions in the air system coupled with excessive moisture in the system probably led to ice formation in the blow system piping. The resulting blockage caused an inadequate blow rate. Consequently, the submarine was unable to overcome the increasing weight of water rushing into the engine room.

Certification SUBSAFE certification is carried out in four areas: Design, Material, Fabrication, and Testing. The exact procedures are documented in the initial design and construction for new submarines, while undergoing routine maintenance in naval depots, and in the fleet maintenance manual for operating submarines. During each step, quality evidence is collected, reviewed, approved, and stored for the life of the submarine. This process is reinforced with external and internal audits.

NASA After the loss of the Space Shuttle Columbia, the Columbia Accident Investigation Board described SUBSAFE as "successful safety programs and practices that could be models for NASA". Following this recommendation, a number of exchanges and conferences were held between SUBSAFE naval personnel and NASA.

See also USS Narwhal (SSN-671), a submarine intentionally not SUBSAFE compliant

References

Worked examples

Example 1 — a first encounter with SUBSAFE

Start with the simplest possible case. Write down what SUBSAFE claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to SUBSAFE before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about SUBSAFE ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of SUBSAFE

In research: SUBSAFE appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses SUBSAFE in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: SUBSAFE is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1963 introductions, Nuclear safety in the United States, Nuclear submarines of the United States Navy, so understanding it makes those chapters shorter.
In everyday life: Look for SUBSAFE outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study SUBSAFE in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what SUBSAFE means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain SUBSAFE out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is SUBSAFE in simple terms?

Why does SUBSAFE matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study SUBSAFE?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on SUBSAFE.