← Back to the archive★ Support my pages
DD-594Spacealso TechFiled Last updated

Deluge Days

Short answer: NASA's Stennis Space Center in Mississippi tests rocket engines and stages by bolting them to giant stands and firing them in place.

Because the hardware doesn't move, the exhaust, which NASA says can reach 6,000 degrees Fahrenheit (about 3,300 degrees Celsius), pours into the same flame deflector for the whole test. Water keeps it from melting. Stennis's high-pressure industrial water system draws on a 66-million-gallon reservoir. For the Space Launch System core stage's Green Run tests in 2020 and 2021, the B-2 stand could receive 335,000 gallons a minute at 300 psi, enough to fill an Olympic pool in about two minutes. Most of it cooled the exhaust through the deflector, and about 87,000 to 92,000 gallons a minute formed a curtain of water to damp noise and vibration. A typical 500-second RS-25 engine test uses about 5 million gallons. Launch pads use water too. At Kennedy Space Center's Pad 39B, the ignition overpressure and sound suppression system dumps about 400,000 gallons in under 30 seconds, peaking around 1.1 million gallons a minute. NASA says SLS produces about 176 decibels at liftoff. The footage looks like a pad water-flow test, with columns of water erupting in front of a steel launch structure.

VideoWrite-up4 sources

In collections:Engineering Oddities

More like this★ Support my pagesCite this file

What should you know about Deluge Days?

Quick facts. Each one stands alone and has a stable ID you can cite.

  1. The B-2 test stand at Stennis can receive 335,000 gallons of water a minute.

    DD-594-F01 · Write-up · Exhibit B (335,000 gallons a minute)

  2. A typical 500-second RS-25 test at Stennis uses about 5 million gallons of water.

    DD-594-F02 · Write-up · Exhibit D (5 million gallons a test)

Video transcript: Deluge Days: Rocket Tests Run on Rivers of Water

DID YOU KNOW? NASA pumps vast amounts of water during rocket tests to protect equipment and ensure safety. At facilities like the Stennis Space Center, rocket engines generate extreme heat and acoustic energy, exceeding 300 decibels. A high volume water deluge system sprays millions of gallons per minute to cool exhaust plumes, reducing temperatures from thousands of degrees Celsius to prevent damage to the test stand. NOW YOU KNOW!

Burned-in captions, read frame by frame (see transcript.md) · 21.3s Reel ·

Video coming soonDeluge Days · Instagram Reel
Deluge Days: Rocket Tests Run on Rivers of Water Instagram Reel · · 21.3s

The write-up

Rocket tests run on rivers of water. Stennis's B-2 stand can take 335,000 gallons of water a minute.

  1. Exhibit A

    Fired in place

    Stennis bolts engines to test stands, so the exhaust hits the same deflector for the whole burn.

  2. Exhibit B

    335,000 gallons a minute

    The B-2 stand's water system can deliver 335,000 gallons a minute at 300 psi.

  3. Exhibit C

    Curtains for sound

    Part of the flow sprays a water curtain to damp noise and vibration.

  4. Exhibit D

    5 million gallons a test

    A typical 500-second RS-25 test uses about 5 million gallons of water.

  5. Exhibit E

    At the launch pad

    Pad 39B's sound suppression system releases about 400,000 gallons in under 30 seconds.

Questions people ask about Deluge Days

Why do test-stand engines need so much cooling water?

Without water, the flame deflector could melt.

Source: Write-up · Exhibit A (Fired in place) · NASA: NASA Stennis Completes Key Test Complex Water System Upgrade; NASA APPEL: Historic Test Stand at Stennis Points Way to the Moon (2019)

How much water a minute can Stennis's B-2 stand receive?

At 300 psi.

Source: Write-up · Exhibit B (335,000 gallons a minute) · NASA APPEL: Historic Test Stand at Stennis Points Way to the Moon (2019)

What does the water curtain around a test stand do?

It protects the hardware from acoustic damage.

Source: Write-up · Exhibit C (Curtains for sound) · NASA: NASA Stennis Completes Key Test Complex Water System Upgrade; NASA APPEL: Historic Test Stand at Stennis Points Way to the Moon (2019)

About how much water does a typical 500-second RS-25 test use?

It all comes from a 66-million-gallon reservoir.

Source: Write-up · Exhibit D (5 million gallons a test) · NASA: NASA Stennis Completes Key Test Complex Water System Upgrade

How much water does Pad 39B release during a launch?

In under 30 seconds.

Source: Write-up · Exhibit E (At the launch pad) · NASA: Pad 39B Water Flow Test Comes Through Loud and Clear (2019); NASA: Launch Pad 39B

Test Your Knowledge

All quizzes →

5 questions, all from this case file. Answers are revealed instantly.

  1. Why do test-stand engines need so much cooling water?

    1. They fire in place, so exhaust keeps hitting the same spot
    2. The engines run on water
    3. To make rainbows
    4. To clean the rocket
    Show the answer

    Answer: A. They fire in place, so exhaust keeps hitting the same spot Without water, the flame deflector could melt. Source: Write-up · Exhibit A (Fired in place) · NASA: NASA Stennis Completes Key Test Complex Water System Upgrade; NASA APPEL: Historic Test Stand at Stennis Points Way to the Moon (2019)

  2. How much water a minute can Stennis's B-2 stand receive?

    1. 335,000 gallons
    2. 3,350 gallons
    3. 33 million gallons
    4. 335 gallons
    Show the answer

    Answer: A. 335,000 gallons At 300 psi. Source: Write-up · Exhibit B (335,000 gallons a minute) · NASA APPEL: Historic Test Stand at Stennis Points Way to the Moon (2019)

  3. What does the water curtain around a test stand do?

    1. Damps noise and vibration
    2. Hides the test from view
    3. Fuels the engine
    4. Cools the control room
    Show the answer

    Answer: A. Damps noise and vibration It protects the hardware from acoustic damage. Source: Write-up · Exhibit C (Curtains for sound) · NASA: NASA Stennis Completes Key Test Complex Water System Upgrade; NASA APPEL: Historic Test Stand at Stennis Points Way to the Moon (2019)

  4. About how much water does a typical 500-second RS-25 test use?

    1. 5 million gallons
    2. 5,000 gallons
    3. 500 gallons
    4. 500 million gallons
    Show the answer

    Answer: A. 5 million gallons It all comes from a 66-million-gallon reservoir. Source: Write-up · Exhibit D (5 million gallons a test) · NASA: NASA Stennis Completes Key Test Complex Water System Upgrade

  5. How much water does Pad 39B release during a launch?

    1. About 400,000 gallons
    2. About 400 gallons
    3. About 4 billion gallons
    4. None
    Show the answer

    Answer: A. About 400,000 gallons In under 30 seconds. Source: Write-up · Exhibit E (At the launch pad) · NASA: Pad 39B Water Flow Test Comes Through Loud and Clear (2019); NASA: Launch Pad 39B

Cite this case file

Easterling, Marcus. "Deluge Days." The Detail Department (DetailEnjoyer), case file DD-594, last updated Jun 12, 2025. https://detailenjoyer.com/case/deluge-days/

Permalink: https://detailenjoyer.com/case/deluge-days/ · Last updated

Markdown version

Cite a single fact by its ID, for example DD-594-F01 → https://detailenjoyer.com/case/deluge-days/#DD-594-F01

Collection · Engineering Oddities Case file 18 of 29

Next in Collection · DD-755Vertical Parking →