Per the video of a Saturn V launch, what happens to the section of the launch platform that’s near the rocket exhaust, is it damaged and needs to be repaired or replaced every time?
According to the NASA site, the pad itself is made of materials which are resistant to the effects. There may be expendable appurtenances.
Recollection from a cape Canaveral tour in the 1970’s:
The Saturn V launch pad had a large A shaped blast deflector made of high strength concrete. This was cooled with water jets. Initially two were made, because it was thought it would likely not survive the first launch. It did survive, and the spare was still sitting near the launch pad, unused, well after the Apollo program had ended.
Just to be clear, there isn’t a flat surface beneath the engines. The term launch “pad” is misleading.
The entire vehicle is supported over a large hole which goes down & then turns horizontally. This is the flame pit & flame trench. It’s huge.
And as **kevbo **said, water is blasted into there at insane volumes during the launch. This cools the exhaust, absorbs noise & vibration, and shields the concrete pit & trench from damage.
The Shuttle uses the old Saturn V launch facilities with some modifications. A couple years ago there was a failure where a bunch of concrete did get blasted off the interior of the pit/trench during a launch. There was immediate concern that some of the debris might have been whipped up and hit the Shuttle while it was still within a few feet of takeoff. Apparently that didn’t happen, or at least didn’t do any serious damage.
Here are some pictures http://images.google.com/images?hl=en&q=canaveral+flame+trench&gbv=2&aq=f&oq=
Watching that video, did anyone else start humming the old MTV theme to themselves?
I’ve got crud burned into old frying pans that a mere rocket exhaust wouldn’t touch. Just make the launch “pad” out of that and it will last forever.
Well, it depends on the type of rocket and the facilities, and the primary concern isn’t so much the facilities as protecting the launch vehicle and payload from damaging acoustic and thermal effects from the reflected plume. For smaller rockets, especially sounding rockets and other suborbital vehicles, there is often just a plume deflector sitting on a flat pad, typically called a “witch hat” which is basically a wedge or pyramid with scarfed sides to push the plume outward. Larger vehicles may use a flame trench, which is a large channel that is evacuated down and then has one or more conduits going to the side to redirect the plume and reflected pressure wave away from the base of the vehicle. Very large rockets like the the Russian R-7/Soyuz, the Apollo family, and the US Space Transportation System (Shuttle) use water-filled trenches as describe here. (Note that while the linked article describes the water being used for “cooling” the flame trench, the primary purpose is actually to attenuate the acoustic shock environment; as energy is absorbed from the plume it turns water into steam which then serves to absorb reflected sound energy.)
A special consideration for military rocket systems is launching from a tube or silo; in such environments the acoustic energy is contained and reflected into the launch vehicle. Some systems, like the LGM-25C ‘Titan II’ and many of the first generation Russian storable liquid systems had a flame deflector that diverted the plume into a pair of exhaust ducts that angled out to the surface. (The HGM-25A ‘Titan I’ was stored in a hardened shelter which was elevated to the surface after loading the cryogenic propellants; however, testing indicated that the missile frame could withstand the silo launch environment, giving the Titan II with storabable liquids a much quicker launch time). Later US solid motor ICBMs like the LGM-30 ‘Minuteman’ family and silo-based ABM systems like the Spartan were just designed to endure silo launch environments; the quicker off-pad time due to higher initial thrust of solid motors combined with a protective thermal protection system (TPS) and the relative thermal insensitivity of these motors made this possible. Later ICBM systems that had limited silo space like the LGM-118A ‘Peacekeeper’ and the liquid Russian R-36M (NATO reporting name SS-18 ‘Satan’), some mobile launch systems like the LGM-134A ‘Midgetman’, and virtually all submarine-based SLBMs like the solid motor Polaris/Poseidon/Trident family, and liquid and solid Russian R29M (SS-N-23 ‘Skif’) and R-39 (SS-N-20 ‘Sturgeon’) missiles, use a cold-gas or warm-gas launch eject system which is basically a large gas pressure generator that pushed the missile out of a launch tube or silo tens of meters or more into the air before igniting the first stage motor. (In the case of an SLBM, this is after going through twenty or more meters of water, allowing the sub to remain protectively submerged.) Although this helps protect the LV and launch facilities, the launch eject transient impulses are large (50-200g) and thus this is ill-suited to delicate satellite payloads or manned launch vehicles.
As for damage done to facilities during launch, it is generally minor. LFs are designed to have some sacrificial elements (expendables) like flexible HVAC conduit, insulation covers (called ‘banana blankets’ or ‘rocket coozies’), and electrical umbilical extensions, but the launch support frame and launch stand are generally made out of a thermally-resistant steel which can withstand the 600-800 degrees C for liquid propellants or several thousand degrees C for solid motors for the short exposure duration (5-10 seconds for liquids, 0.5-2 seconds for solid or solid-augmented motors). This will certainly strip off paint, and the acoustics may loosen some non-critical elements like covers that have to be replaced, but the main structure shouldn’t see thermal or erosive damage. Expendable launch frames and adaptors that are attached to the vehicle may be made from aluminum, but these are not intended to be reused and generally only need to demonstrate structural integrity during transportation and emplacement. Occasionally you’ll have concrete pad or trench break or spall, which is undesirable from a foreign object damage (FOD) perspective, but that is pretty easily fixed.
On the other hand, if a rocket explodes on pad–which doesn’t happen very often, but it dramatic when it does–launch facilities can be damaged beyond repair, requiring complete tear-down and reconstruction. This is obviously expensive and for an LF that is intended to be reused, very undesirable. But since rockets aren’t supposed to explode and it would be difficult to impossible to build a large launch support frame or silo that is completely blast-proof, this isn’t a design criteria.
Stranger
I also toured the Cape Kennedy site some years ago, that was a short time after the first shuttle explosion during launch, so, some areas apparently usually accessible to visitors were now off limit. The tour guide did point out the flame trench and mention the spraying of water during a launch.
However, after watching the video in the OP, one question comes to mind.
In the video, we see some connections on the support tower breaking away as the Saturn rocket starts to rise and some support structures retracting, however, I would think that those can’t retract enough to avoid being damage by the intense heat of the rocket engines.
I assume that the setup for the shuttle uses similar connections, I also assume that these connections are electrical wires and hoses of some kind, most likely rubber and would surely melt.
Well Stranger_on_a_Train has addressed my concern while I was busy typing it in. Thanks.
What do they do for the sea launch systems? I think Arianne used those and maybe they still do.
Arianespace launches exclusively from Centre Spatial Guyanais in French Guiana. The Sea Launch Partnership launches off of a towed platform with an open bottom from near Christmas Island. The Russian Shtil’ performs satellite launches out of a submarine by the previously mentioned methods and (presumably) a hell of a payload shock isolation system. Smaller target vehicles are launched off of the deck of a towed barge with a witch hat deflector; this is especially true with foreign military assets (FMAs) that have caustic reactant products.
Stranger
“Smaller target vehicles are launched off of the deck of a towed barge with a witch hat deflector; this is especially true with foreign military assets (FMAs) that have caustic reactant products.”
Now that is a fascinating comment…
Care to elaborate? Are you allowed to?
Storable liquids have the nice property that the don’t tend to boil off; however, most storables, like unsymmetrical dimethyl hydrazine (UDMH) and inhibited fuming red nitric acid (IRFNA) are even nastier than they sound, and their reactant products are toxic and caustic. Most US launch facilities, like Vandenberg AFB, Cape Canaveral AFS and Kennedy Space Center, and White Sands Missile Range, are on or near protected sanctuaries or national monuments, which means that the ecological crowd is (often rightly) concerned about incidental damage and contamination. However, there are far fewer restrictions from launching even caustic fuels in mid-ocean.
Stranger