# What's the deal with the shuttle's post-flight 'diaper'? **URL:** \ **Category:** Factual Questions\ **Created:** [April 18, 2009, 4:54am UTC](https://boards.straightdope.com/t/whats-the-deal-with-the-shuttles-post-flight-diaper/493508 "2009-04-18T04:54:14Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![NinjaChick](https://avatars.discourse-cdn.com/v4/letter/n/71c47a/32.png) [@NinjaChick](https://boards.straightdope.com/u/NinjaChick)\ **Post date:** [April 18, 2009, 4:54am UTC](https://boards.straightdope.com/t/whats-the-deal-with-the-shuttles-post-flight-diaper/493508/1 "2009-04-18T04:54:14Z")
For lack of a better term. Sometime between landing and [mating](http://en.wikipedia.org/wiki/File:Shuttle_mate_demate_facility.jpg) with the jet that carries it back to Florida, a boxy structure is strapped to the back of the space shuttle, covering the engine nozzles. What’s the purpose of this cover? The two that pop into my mind - protecting the nozzles/engines or reducing drag during the flight - strike me as slightly absurd. I can’t imagine that the hitched ride would put any significant stress on something that can withstand launching itself into space, and I’m pretty sure that if you strap one plane to the back of another, you’re going to have some crazy drag to begin with. ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [April 18, 2009, 5:11am UTC](https://boards.straightdope.com/t/whats-the-deal-with-the-shuttles-post-flight-diaper/493508/2 "2009-04-18T05:11:29Z")
> [@NinjaChick](#): > > I’m pretty sure that if you strap one plane to the back of another, you’re going to have some crazy drag to begin with. True. But if you put enough drag on an aircraft it isn’t going to fly. The fairing is for drag reduction. [http://www1.dfrc.nasa.gov/Gallery/Movie/STS/HTML/EM-0084-02.html](http://www1.dfrc.nasa.gov/Gallery/Movie/STS/HTML/EM-0084-02.html) > [@](#): > > For the first three flights, a tail cone was placed around the dummy main engines to reduce buffeting. ---
**Author:** ![yoyodyne](https://avatars.discourse-cdn.com/v4/letter/y/a9a28c/32.png) [@yoyodyne](https://boards.straightdope.com/u/yoyodyne)\ **Post date:** [April 18, 2009, 5:15am UTC](https://boards.straightdope.com/t/whats-the-deal-with-the-shuttles-post-flight-diaper/493508/3 "2009-04-18T05:15:47Z")
> [@NinjaChick](#): > > I’m pretty sure that if you strap one plane to the back of another, you’re going to have some crazy drag to begin with. In addition to minimizing the crazy drag, it reduces the turbulence of the air to the 747’s vertical stablilizer. ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [April 18, 2009, 5:18am UTC](https://boards.straightdope.com/t/whats-the-deal-with-the-shuttles-post-flight-diaper/493508/4 "2009-04-18T05:18:54Z")
> [@yoyodyne](#): > > In addition to minimizing the crazy drag, it reduces the turbulence of the air to the 747’s vertical stablilizer. Whoops! I meant to include that in the edit. :smack: ---
**Author:** ![Hail\_Ants](https://avatars.discourse-cdn.com/v4/letter/h/dc4da7/32.png) [@Hail\_Ants](https://boards.straightdope.com/u/Hail_Ants)\ **Post date:** [April 18, 2009, 5:39am UTC](https://boards.straightdope.com/t/whats-the-deal-with-the-shuttles-post-flight-diaper/493508/5 "2009-04-18T05:39:32Z")
> [@yoyodyne](#): > > In addition to minimizing the crazy drag, it reduces the turbulence of the air to the 747’s vertical stablilizer. Even so, flying with the Shuttle on its back the 747 carrier aircraft has to have extra vertical stabs on [both ends of its horizontal stabilizer.](http://commons.wikimedia.org/wiki/Shuttle_Carrier_Aircraft) ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [April 18, 2009, 2:48pm UTC](https://boards.straightdope.com/t/whats-the-deal-with-the-shuttles-post-flight-diaper/493508/6 "2009-04-18T14:48:48Z")
> [@yoyodyne](#): > > In addition to minimizing the crazy drag, it reduces the turbulence of the air to the 747’s vertical stablilizer. It’s actually more for this purpose than net reduction of drag. Even with this, the Shuttle Carrier Aircraft (SCA) only has a range of about 1,000 miles with the Orbiter on top, meaning it has to stop three times for a cross-country delivery. I believe there were plans to fit the aircraft for aerial refueling at one point but the cost of providing fueling services and the risk of a mid-air collision made it prohibitive. Stranger ---
**Author:** ![NinjaChick](https://avatars.discourse-cdn.com/v4/letter/n/71c47a/32.png) [@NinjaChick](https://boards.straightdope.com/u/NinjaChick)\ **Post date:** [April 18, 2009, 7:55pm UTC](https://boards.straightdope.com/t/whats-the-deal-with-the-shuttles-post-flight-diaper/493508/7 "2009-04-18T19:55:16Z")
> [@Stranger\_On\_A\_Train](#): > > It’s actually more for this purpose than net reduction of drag. Even with this, the Shuttle Carrier Aircraft (SCA) only has a range of about 1,000 miles with the Orbiter on top, meaning it has to stop three times for a cross-country delivery. I believe there were plans to fit the aircraft for aerial refueling at one point but the cost of providing fueling services and the risk of a mid-air collision made it prohibitive. > > Stranger Huh, I’d always just assumed it was a straight shot back, but that makes a lot of sense. Out of curiosity (since it seems you know something about it) does NASA have special training specifically for that? I mean, it must be incredibly different and much harder to fly that than a regular 747. ---
**Author:** ![yoyodyne](https://avatars.discourse-cdn.com/v4/letter/y/a9a28c/32.png) [@yoyodyne](https://boards.straightdope.com/u/yoyodyne)\ **Post date:** [April 19, 2009, 4:55am UTC](https://boards.straightdope.com/t/whats-the-deal-with-the-shuttles-post-flight-diaper/493508/8 "2009-04-19T04:55:35Z")
> [@Stranger\_On\_A\_Train](#): > > It’s actually more for this purpose than net reduction of drag. More for drag really. Listen to this [podcast](http://media.libsyn.com/media/airspeed/AirspeedSCA2.mp3) interview with SCA pilot and astronaut Gordon Fullerton. ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [April 19, 2009, 5:11am UTC](https://boards.straightdope.com/t/whats-the-deal-with-the-shuttles-post-flight-diaper/493508/9 "2009-04-19T05:11:06Z")
> [@NinjaChick](#): > > Huh, I’d always just assumed it was a straight shot back, but that makes a lot of sense. Out of curiosity (since it seems you know something about it) does NASA have special training specifically for that? I mean, it must be incredibly different and much harder to fly that than a regular 747. Yes, pilots for the SCA are specially trained to fly that aircraft, and the aircraft itself is extensively modified for this purpose. The original plan was to use a purpose designed ‘flying barge’ into which the Orbiter would fit, but the SCA turned out to be much cheaper and could be used for atmospheric flight tests. The C-5 Galaxy was also considered, but because it would have been an Air Force asset NASA would not have retained ownership and would have been at the mercy of the former for flight operations, whereas the 747 is a commercial airframe that has remained in production. > [@yoyodyne](#): > > More for drag really. Listen to this [podcast](http://media.libsyn.com/media/airspeed/AirspeedSCA2.mp3) interview with SCA pilot and astronaut Gordon Fullerton. The information I have indicates that it was done primarily to protect the stabilizer (a significant problem) but no doubt it significantly reduces drag as well; those two effects are hand-in-hand, as the turbulence that would cause stabilizer problems would also substantially increase parasitic drag. Stranger ---
**Author:** ![Rhubarb](https://avatars.discourse-cdn.com/v4/letter/r/59ef9b/32.png) [@Rhubarb](https://boards.straightdope.com/u/Rhubarb)\ **Post date:** [April 19, 2009, 6:40am UTC](https://boards.straightdope.com/t/whats-the-deal-with-the-shuttles-post-flight-diaper/493508/10 "2009-04-19T06:40:15Z")
So what you’re saying is that it’s not a diaper, it’s a Speedo. ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [April 19, 2009, 2:00pm UTC](https://boards.straightdope.com/t/whats-the-deal-with-the-shuttles-post-flight-diaper/493508/11 "2009-04-19T14:00:58Z")
I was reading the [Wikipedia article about the SC](http://en.wikipedia.org/wiki/Shuttle_Carrier_Aircraft)A, and came across this tidbit: > [@](#): > > The aircraft was extensively modified by Boeing in 1976. Its cabin was stripped, mounting struts added, and the fuselage strengthened; vertical stabilizers were added to the tail to aid stability when the Orbiter was being carried. The avionics and engines were also upgraded, and an escape tunnel system similar to that used on Boeing’s first 747 test flights was added. The flight crew escape tunnel system was later removed following the completion of the Approach and Landing Tests (ALT) due to **concerns over possible engine ingestion of an escaping crew member**. :eek: ---
**Author:** ![Rhythmdvl](https://avatars.discourse-cdn.com/v4/letter/r/85f322/32.png) [@Rhythmdvl](https://boards.straightdope.com/u/Rhythmdvl)\ **Post date:** [April 19, 2009, 2:36pm UTC](https://boards.straightdope.com/t/whats-the-deal-with-the-shuttles-post-flight-diaper/493508/12 "2009-04-19T14:36:02Z")
Anybody else get a kick out of the _ **SCA** _ being responsible for carting about such a high-tech piece of equipment?