Tag Archives: Langley Research Center

Vibrations and Loads

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It may be pretty obvious, but it’s worth noting that one of the main purposes of a flight test is to do a little trailblazing. We can and should test processes and procedures as early in a program as possible so we can identify any areas for concern and target problem spots that need some improvement. The more we build and fly, the more we learn. As a flight test, Ares I-X is doing that exact thing for the Ares I rocket.

One aspect of rocket building that we are paying special attention to lately is vibration. Rockets vibrate a lot. In the case of Ares I-X, the vibrations come from several sources. Among them are the vibration and sound waves caused by the lift off of the rocket, the burning of rocket propellant and the act of plowing through the atmosphere at over four times the speed of sound.

The vibration that is produced by the burning of the solid rocket propellant in the first stage booster is called thrust oscillation. These vibrations — or oscillations — come in the form of waves, which travel up and down the length of the rocket like a musical note through an organ pipe. One of the biggest challenges in any rocket design is developing avionics (aviation electronics) that can function in this vibrating environment.

Vibration is not just a rocket issue, though. All electronic hardware is tested for its ability to handle shock and vibration. An MP3 player, for example, has to be tested for its ability to handle the vibrations from someone walking or jogging while holding it, placing it on a countertop, or accidentally dropping it on the floor. However, compared to the workout that Ares I-X’s avionics receive, your MP3 player has got it easy. Imagine shaking that MP3 player inside an automatic paint can shaker for two minutes while continuing to play your favorite tunes. That’s kind of what the electronics of the I-X are up against.

Two of the most important sets of electronics on Ares I-X are the thrust vector control (TVC) system, which steers the rocket, and the flight termination system (FTS), which is used to “self destruct” the rocket if it veers off its proper flight path.

Recently, NASA engineers at Langley Research Center upgraded to a new, higher-precision computer model, which allowed them to more closely examine the vibration environments on Ares I-X. With this more precise model, they observed that some areas of the rocket had vibration levels — called “G-loads” or just “loads” in engineer-speak — that were slightly higher than the levels the TVC and FTS were initially tested to handle.

How much is “slightly?” Well, Langley’s engineers are still examining the computer models to get the full answer, but right now the observed vibration levels are measured in hundredths of a gravity (or “G”). That would be like giving the automatic paint shaker one extra shake every minute — you wouldn’t notice the difference, but your MP3 player might.

The computer models have found that the biggest effects of the thrust oscillation on Ares I-X come between 70 and 90 seconds into the flight, when the rocket is about three fourths of the way through its ascent. Before 70 seconds and after 90 seconds the vibration levels are fine, but for those 20 seconds we haven’t fully verified that we can still steer the rocket with the TVC or send the signal to self-destruct the rocket and end the flight with the FTS if it veers away from its projected path.

So that’s the challenge the Ares I-X team is facing right now. Fortunately, we have several options for handling the situation, and the I-X team is looking at all of them to determine the best way forward:

  • First, the team is analyzing the new vibration models more closely to make sure that the components really do exceed their limits, and if so, by how much.
  • Next, if the team determines that the vibrations do exceed the design limits of the TVC or FTS, test engineers could re-test the components to operate at the higher vibration loads. If the components pass the re-testing, the stacking and assembly of the rocket will continue as planned.
  • However, if the test team finds that the avionics could still have problems at the higher vibration levels, they may need to make some modifications to the vehicle like adding additional support structures to dampen the vibrations or isolate the hardware from the vibrations’ effects.

Since the beginning of the I-X mission, NASA has worked very closely with the Air Force’s 45th Space Wing’s Range Safety team, which controls the range at Kennedy Space Center to make sure that every precaution is taken to ensure a safe launch and a safe flight. The 45th Space Wing will continue to work alongside the I-X team to evaluate the situation and make sure that the best decision is made.

The bottom line is that we’re not launching anything until it’s deemed safe by NASA and the U.S. Air Force, even if it takes a little longer to get it right. We’re all excited about watching Ares I-X take flight later this year, but really, we might end up learning just as much from these steps along the way as we do on launch day.

The CM-LAS and the Birdcage

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Ares I-X hardware has the best nicknames.

These images show the Stack-5 Ground Support Equipment Lifting Fixture or as it is known to the I-X team, the “birdcage” being lowered over the Crew Module/Launch Abort System (CM/LAS) for a fit check. The birdcage is a metal framework that was collaboratively built and designed at the Langley Research Center in Langley, Virginia and Kennedy Space Center in Florida. It fits over the CM/LAS in order for it to be moved and stacked creating super stack 5.

The “birdcage” is bolted to the bottom of the crew module portion of the CM/LAS and then lifted into place (by one of the 325 ton overhead cranes in the VAB) and placed on top of the service module, which is already stacked on top of the Ares I-X rocket.  Technicians can then remove the bolts — from inside the CM — and the “birdcage” is removed.

NASA Langley Ares I-X Rocket Elements Arrive at NASA Kennedy Space Center

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It takes a mighty big airplane to transport a 43-foot-long piece of hardware, not to mention a 16 foot wide, 7 foot tall simulation of the crew module that will take our astronauts to the moon.


The Ares I-X launch abort system (LAS) simulator rolled off an Air Force C-5 transport Jan. 28 after landing on the NASA Kennedy Space Shuttle runway.  The LAS simulator, which represents the tip of the Ares I-X rocket, was designed and built at NASA Langley Research Center. 

The Ares I-X crew module, in blue, and supporting hardware were unloaded after the two-hour flight from Langley to Kennedy.

The crew module and launch abort system simulators, wrapped in blue, took their place among other Ares I-X hardware in the Vehicle Assembly Building at NASA Kennedy. 

Ares I-X Media Event at Langley Research Center

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About the Author:  Keith Henry serves as a Public Affairs Officer at NASA’s Langley Research Center.


Reporters gathered yesterday to see recently completed Ares I-X flight hardware on display at NASA Langley Research Center. The hardware, which was designed and built at Langley, is engineered to represent the outer surface of Orion crew module and a launch abort system that will increase crew safety on the Ares I rocket. Next week, the rocket hardware pieces will be shipped from Langley to NASA’s Kennedy Space Center in Florida.

The simulated crew module and launch abort system will complete the nose of the rocket. As many as 150 sensors on the hardware will measure aerodynamic pressure and temperature at the nose of the rocket and contribute to measurements of vehicle acceleration and angle of attack.

The data will help NASA understand whether the design is safe and stable in flight, a question that must be answered before astronauts begin traveling into orbit and beyond.

See construction videos and images on the Ares I-X Web site.

Media Day Photo: While workers put the finishing touches on the Launch Abort System, left, and Crew Module simulators, reporters interviewed project officials and photographers and videographers captured the moment. The rocket elements are being placed on special flatbed trailers which will be rolled onto an Air Force C-5 for a two-hour flight to NASA Kennedy Space Center Jan. 28.