The STS-126 mission will resume ISS operations after a break for STS-125’s flight to the Hubble Space Telescope, but one of the newest additions to the mission plan won’t take place until reentry.
The mission’s Program Freeze Point was overviewed at the PRCB (Program Requirements Control Board) meeting earlier this month, where a Boundary Layer Transition (BLT) Detailed Test Objective (DTO) was proposed.
**The most comprehensive collection of Shuttle, Ares, Orion and ISS related presentations and mission documentation, plus expansive daily processing documentation and updates are available to download on L2 **
L2: STS-122 to STS-127 documentation already available.
STS-122 L2 Special NOW LIVE. **Click here for sample of L2 menu and content**
**STS-122 Special: 12 MOD Flight Readiness Review (FRR) Presentations, Baselines and Mission Overviews. 17 Shuttle FRR Presentations. Payload Presentations and vast amounts of live, uploaded images and presentations. Installation Movies (several) – already 1700 megabytes strong**
**COMPLETE Section on ECO/Feedthrough Connector issues and troubleshooting, graphical and data based – expansive.**
**LIVE updates on Atlantis STS-122 Troubleshooting Latest**
**LIVE updates on Discovery STS-124 Processing**
**LIVE news updates on Endeavour STS-123 Processing**
**Click here for FRR overview articles: Article 1 – Article 2** – Click *HERE* for all our articles on the STS-122 ECO/Feedthrough Connector issue.
During re-entry, the compression of air on the leading edge of the space shuttle forms a protective ‘blanket’ around the orbiter. Temperatures within that region are a manageable 2-3,000 degrees, while just a few inches away the full force of heating results in readings of up to 10,000 degrees.
As long as the orbiter’s surface is smooth, the boundary layer keeps tile heating within the limits of their design, but any interruption in the air flow causes a boundary layer ‘trip’ where turbulence behind the trip point brings in the extreme heat to the tiles, and could cause tile failure and/or damage to the underlying surface.
Picture a smooth flowing river and water moving uniformly downstream, then place a large rock in the middle and you’d observe the water behind the rock swirling around. Everything ahead of the rock stays in a steady state, but the water past the rock is very turbulent.
When the shuttle team finds a gap filler or tile damage on the underside of the orbiter, they have to determine if that ‘change in smoothness’ will trip the boundary layer, at what speed it will be impacted, what sort of temperatures will impinge upon the tiles, and what damage (if any) will result.
Unfortunately there is very little research into this area. There are a lot of computer simulations, but very little actual experiments to validate the models.
**Ride home through the fire, sparks and plasma of re-entry with Atlantis, Discovery and Endeavour. FIVE Stunning high quality 2hr, 355-400mb Camcorder and HUD videos – from payload bay closure – through re-entry with an astronaut held camcorder video – to post landing – several more videos showing landing from 90,000 ft also available and HUD videos from STA landings. Now includes HALO II Re-entry video, and re-entry videos from Gemini and Apollo (converted from 8mm)**
The orbiter involved, Endeavour, is multi-tasked with STS-326 rescue support for STS-124, will also be the last shuttle to sit on launch pad 39B as STS-400 – the rescue support for STS-125’s Hubble mission – and will be the heaviest logistics flight ever, STS-126, carrying supplies – including a new six-crew Galley – to the ISS.
As noted in the expansive 81 page presentation – available to download on L2 – STS-126 is proposed to be the first mission with a specific test installed to measure the impacts of a boundary layer transition, with the DTO utilizing a specially designed tile to ‘trip’ the boundary layer – along with instrumentation underneath tiles downstream that would measure any thermal impacts.
A specially designed ‘trip tile’ will be installed near the main landing gear door, with a roughly one-quarter inch protuberance, to trip the boundary layer at speeds less than or equal to Mach 15.
Current DAT (Debris Analysis Team) assessments have cleared the orbiter up to Mach 18. so it’s been classified as a low risk to mission safety.
Thermocouples will be installed underneath the tile on the left-hand wing and downstream of the trip tile to measure the specific temperatures during reentry.
The tile is being installed in a location where studies show that even a very large break in the boundary layer will not be a concern. If Arcjet testing of the setup – scheduled for mid-January – shows any reason for concern, the tile can be removed late in the OPF (Orbiter Processing Facility) flow if necessary.
Since Return To Flight, there have been 1093 hits to the bottom of the orbiter, but only one in this area – so additional damage during launch is not expected. Ten thousand simulations of foam debris striking the area produced no critical damage in any.
However, if something does happen, that would make the test an issue on flight, EVA tools and techniques have been tested in case the protuberance needs to be removed.
Future plans call for installing the thermocouples on Discovery as well, and beginning her testing with a half-inch protuberance on STS-127 – for a transition closer to Mach 18. The last test in Phase I is a three-quarter inch notch on STS-128, which would transition at Mach 19.
Phase II testing will add a catalytic coating material on one of the tiles which would gather catalytic / turbulent heating interaction data.
Two additional flights are on the manifest through the end of the shuttle program – based on current manifest – which are currently being penciled in as contingency flights for this experiment.
The overall goal is not just to help shuttle operations. There is little understanding of boundary layer transitions, and the data from this experiment is expected to strongly impact development of computational techniques.
The results will impact many other thermodynamic interests in the aerospace fields.
L2 members: All documentation – from which the above article has quoted snippets – is available in full in the related L2 sections, updated live.
**STARLIGHT: NEW STS-117 MISSION REVIEW MUSIC VIDEO** – STS-118 and STS-120 Mission review video also available.
**ROCK YOU LIKE A HURRICANE: STS-117 MISSION REVIEW MUSIC VIDEO – AS SEEN BY THE STS-117 CREW!!** -.
(Video section is FREE, but you need to sign up as a member of the forum to enter the video section of the site. We only use your e-mail to send you your password. It will not be used for spam etc.)