T-11 hours Hold

Right now NASA is in the middle of the T-11 hours hold (more info on shuttle countdowns), a built-in hold of 13 hours 22 minutes, with the following main tasks to be accomplished:

  • Weather and engineering briefings
  • Pad debris inspection and closeout
  • Flight crew equipment late stow
  • Move rotating service structure to “park” position
  • Activate the orbiter’s inertial measurement units and communications systems
  • Perform ascent switch list

Sometime today, the official launch time was shifted one second, but the planned launch is still 3:47 p.m. EDT Friday which is in the middle of the ten minute launch window. During the planned T-9 minute hold, the shuttle managers will make adjustments to the launch time as required.
If you want the current mission minutiae, watch STS-134 – Countdown Status Briefing April 28.
The countdown will resume at T-11 hours (11:22 p.m. EST).
The weather forecast calls for a 70 percent chance of favorable conditions at launch time – so pray for mojo.
As a personal matter, I’m in Orlando now, in the suburban oasis which is the airport Holiday Inn.

On the Space Shuttle External Tank

Space Shuttle External Tank Above Earth (NASA, File Photo)
The very large, very orange, object on the Space Shuttle stack is the External Tank (ET) which holds fuel in the form of iquid hydrogen (LH2) fuel and liquid oxygen (LO2) oxidizer which mix in the three Space Shuttle Main Engines (SSME). The ET is the only non-reusable lift object: the ET is jettisoned just over 10 seconds after Main Engine Cut Off (MECO).
STS External Tank

Above: the External Tank. The right hand pipe is the LO2 feedline which enters the shuttle near the orbiter LH2 feedline and umbilicals at the aft attachment point.

The ET is covered in foam in order to keep the fuel liquid – this is the same foam which cause the catastrophic loss of the Space Shuttle Columbia when during liftoff a suitcase-size piece of thermal insulation foam broke off from the ET, striking Columbia’s left wing panels. The specific piece of foam which broke off (the Left Bipod Foam Ramp) was designed to reduce aerodynamic stresses around the bipod attachment to the shuttle, and on further missions this piece was removed from design and flight.
External Tank Diagram
There are three main parts to the ET: the iquid hydrogen (LH2) fuel tank (bottom), liquid oxygen (LO2) oxidizer tank (top) and the intertank connecting the two pieces. The large exterior line is the LO2 feedline which is 17″ in diameter which is connected to the space shuttle at the bottom mating points.
The specific ET which is being flown on STS-134 is ET-122 which was refurbished after damage during Hurricane Katrina, being fully certified and flight-worthy. As a NASA manager stated, It might not be pretty, but it is fully flight ready. To mark the return of ET-122 to flight-worthy status, Lockheed Martin created a Return to Flight logo which was applied to the Intertank Access Door at the request of NASA, the first of its kind. The logo is below (courtesy of Lockheed Martin):
ET-122 Insignia
Below are photos of the ET, LO2 Feedline, and space shuttle mating section:

ET-122 Rollout to Barge (NASA, 9/20/10) by NASA’s Marshall Space Flight Center:

ET-122 Rollout to Barge (NASA, 9/20/10)

External tank-shuttle bipod:

ET Bipod

17″ O2 Feedline at Top of the External Tank:

External Tank O2 Feedline

LH2 Feedline (O2 Feedline behind) at orbiter aft attachment point:

ET-Orbiter Connections
More information

This is another in a series of posts documenting my time around the liftoff of STS-134 Space Shuttle Endeavour. For more posts, check out my STS-134 Launch Page.
Smogr watches STS-134 Space Shuttle Endeavour

How Does the Space Shuttle Stay on the Pad? Eight. Big. Bolts.

Short answer: eight giant bolts.

Long answer: the Space Shuttle is attached to the External Tank (ET) which is attached to the two white Solid Rocket Boosters (SRB) which is bolted to the mobile launcher platform (MLP) with eight 28″ long (3.5″ diameter) bolts, four on each SRB. At T-6.6 seconds the Shuttle main engines (SSME) ignite, and then at T-0, the SRBs ignite; the bolts are detonated releasing the combined Shuttle stack.

If you look at the below photo of the space shuttle Enterprise sitting on the MLP, you can see how the orbiter hangs from the external tank which is attached to the solid rocket boosters:

Space shuttle Enterprise First Appearance
shuttle drawing

Below are photos of the SRBs and the hold-down posts (all photos by Steve Patlan):

Shuttle Stack in VAB

SRB Skirt

SRB Hold-Down Post

Also note that when the main engines ignite, the direction of thrust is off vertical axis, which causes the shuttle stack to do what is called the “Shuttle Twang,” tilting forward and then settling back vertical (this is why the main engines fire at T-8 seconds). Here’s a video of the external tank in real-time:

Update: Here’s a photo from the bottom of the flame trench of the business-end of the SRB. Note the two Sound Suppression Water System (SSWS) nozzles on the left side.

SSRB flame trench

More Information:

This is another in a series of posts documenting my time around the liftoff of STS-134 Space Shuttle Endeavour. For more posts, check out my STS-134 Launch Page.
Smogr watches STS-134 Space Shuttle Endeavour

STS-134 Launch

STS-134 + AMS Patches
Next week I will be heading down to Florida to (hopefully) watch the launch of STS-134 Space Shuttle Endeavour. STS-134 is the penultimate voyage of the Space Shuttle utilizing Endeavour, deilvering payload to Space Station consisting of the Alpha Magnetic Spectrometer (AMS-2) and ExPRESS Logistics Carrier (ELC-3), performing four spacewalks (EVA) and performing various experiments, including STORRM DTO and GLACIER Freezer Module.
Just like when I went to the Johnson Space Center STS-130 Tweetup to meet astronauts and cool NASA people, I’ll be posting photos, interviews and commentary. Follow my updates right here on Smogr, or on my STS-134 Launch Page, which will aggregate my Twitter updates, and Flickr photos.
Smogr watches STS-134 Space Shuttle Endeavour

How the Trading Places Final Scene Works

Ever wondered how Louis & Valentine bankrupted the Dukes and made their fortune in Trading Places? Well, Straight Dope user Billdo explains commodity trading:

Commodity futures are a little different. With futures, you promise to buy or sell the physical commodity at at a specific date for a specific price (For example, Frozen Concentrated Orange Juice for December 1 delivery at $100). Everyone in the market is either promising to buy or sell on the delivery date at the specified price. Unless you actually produce FCOJ, or use FCOJ in your business, you are trading speculatively. Unless you match the number of contracts you’ve sold and the number you’ve bought by the delivery date, you will have to pony up the OJ (or buy it) at that date (though actually you’ll probably be able to buy or sell the OJ on the spot market if you cannot deliver or use the physicals, though the spot market price can vary significantly). Needless to say, commodity future trading is very risky (and is subject to the same sort of margin calls as short selling of stock).

Now what Ackroyd/Murphy did was initially sell contracts for delivery at a later date. That is to say, they promised that by the delivery date they would get enough OJ by the delivery date to cover their contracts, either by obtaining the physical OJ, or by buying offsetting contracts in the market. When everybody thought there would be little OJ supply, the price of this promise to sell and deliver was very high. When everybody found out there would be ample supply, the price of this promise to deliver dropped significantly. After the price dropped, they bought back offsetting contracts for delivery (or looked at another way, they got a promise that they could buy the same amount of OJ at the delivery date that they had earlier promsed to sell). Having equalized their position, they could leave the market with the money they made.

Now when you’re in the market with more promises to sell than promises to buy, you’re known as having a short position, and if you have more promises to buy, you’re known as having a long position. In some ways this is similar to having a short position in stock or long position in stock (actually owning the stock), but the key difference is that there is an actual delivery date called for.

Now you too can win the $1 bet.