49 votes
Accepted

Why isn't SpaceX constructing the Super Heavy launch mount on top of the water?

Salt does all sorts of unpleasant things to just about every building material humans use. Hot salt spray, such as you'd get from a rocket launch, is even worse: spraying something with hot saltwater ...
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  • 11.6k
47 votes
Accepted

Will the Falcon Heavy be far enough in 12 seconds to not cause damage?

Not even close. In fact, at 12 seconds in, you're looking at maximum damage to not just the pad itself, but the surrounding area as well. You're going to have tons of debris (most of it burning and ...
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  • 6,810
44 votes

Why do Crew Dragon astronauts need to climb up one level using the stairs before ingress?

Scott Manley of the YouTube has a great video that addresses the extra level of the tower, located at the seven minute mark of a recent posting. Verbatim transcript from the video: So pad 39A is ...
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  • 1,850
34 votes
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Why does the CRS-8 Falcon 9 rocket appear to be swaying before launch?

Because it is. It is a very tall structure, first stage alone is 140 feet, plus second stage, plus fairing. It is considered at the limit of how tall and thin they can make it. Wikipedia says the ...
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  • 76.7k
30 votes
Accepted

How close can I get to a rocket launch and not get killed?

The American Petroleum Institute, in its standard 521, outlines limits for exposure of personnel to heat radiation from flares. As hydrocarbons and hydrogen are commonly flared, and also commonly used ...
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26 votes

What kept crosswinds from pushing Apollo rockets into their own gantry?

The clearances were calculated to be OK up to a 95th percentile wind. I assume there was a Launch Commit Criteria (LCC) for the ground wind, but I have not been able to find an Apollo LCC document. ...
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19 votes

What exactly is the purpose of connection links strapped between the rocket and the launch pad

In general, umbilicals are provided from the launch pad to the vehicle for any services that need to be provided after the vehicle is installed on the launch mount, and to remove hazardous gases from ...
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17 votes
Accepted

How can a rocket go straight up after ignition?

Rockets can use different systems for attitude control (control thrusters, fins, gyroscopes, TVC, ...). Since you ask for the seconds after liftoff, the relevant system is TVC (Thrust Vector Control). ...
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  • 1,324
16 votes

What controls hold-down clamp release: rocket... or ground control?

For shuttle it was commanded by the vehicle computers. At T-31 seconds control of most remaining countdown events was handed over to the vehicle, including SRB ignition and blowing the hold-down post ...
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15 votes
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Do strongbacks/launch towers have to be repainted or refurbished after a launch?

On e.g. the Saturn and Shuttle launches, vulnerable items like umbilicals are retracted into closed spaces, with a door closing over them in time to protect them. This very detailed video of a ...
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  • 122k
15 votes

Why are rocket mass on the launch pad and payload mass to LEO not strongly correlated?

It typically takes a total expenditure of 9400-10000 meters per second of delta-v to reach LEO. Per the rocket equation, delta-v is proportional to the log of the propellant mass ratio, but also ...
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14 votes
Accepted

Were launchpads at KSC built with pilings or footings?

Based on this article, 39A is just concrete on top of sand. That does seem a little ridiculous though. The pumps piled up another portion of the dredged sand on the launch pad, creating a flat-...
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  • 156
14 votes
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What controls hold-down clamp release: rocket... or ground control?

For Apollo, the signal came from a small computer room built inside the mobile launch platform. Giant holddown arms, whose name exactly describes their function, are positioned on the launcher ...
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  • 46.6k
13 votes

Why do KSC crawler-transporters use caterpillar treads instead of rail tracks?

Weight distribution would be be the main reason. The Shuttle stack (or Saturn V stack) empty, weighed an immense amount. Shuttle more so, since the SRB's were full during movement. (Can't fuel a ...
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  • 76.7k
13 votes

Why would someone need vertical loading for a SpaceX rocket?

I didn't dig too hard for sources because this is probably a very minor expansion on top of the other answers, but WHICH payloads might require vertical integration? Ones with big stinking mirrors ...
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  • 4,516
12 votes

Will the Falcon Heavy be far enough in 12 seconds to not cause damage?

To avoid damage to the pad, the rocket must have traveled down range far enough that if it exploded, the debris would not land back on the pad. The issue isn't height, it's horizontal distance. 12 ...
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12 votes
Accepted

How are umbilical connectors held in place until their intended detachment?

This paper surveys a large number of umbilical designs. For the mechanical connections to the vehicle, it lists two types of detachable locking devices. The type of locking mechanism ...
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12 votes

Why isn't SpaceX constructing the Super Heavy launch mount on top of the water?

Environmental impact may be a major consideration The effect on the local water environment from that sort of blast into it could be severe and far reaching in the neighborhood around a water based ...
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11 votes
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How close can I get to a rocket launch?

The closest launch to the public for an orbital launch is almost certainly the one you listed, Baikonur. I'm quite confident that for people outside, that is probably about the closest you can get as ...
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  • 119k
11 votes

Was LC39A built with a rocket much larger than the Saturn V in mind?

Launch Pads 39A and 39B were initially built for either the Saturn C-8 or the Nova rockets, each of which has a lift off thrust of about 7000 tons, about twice that of the Saturn V. These were ...
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  • 119k
11 votes

What pushes back on rockets?

Newton's Third Law states that if object A pushes on object B with a certain amount and direction of force then object B pushes on object A with same amount and opposite direction of force. Notice ...
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  • 46.6k
10 votes
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Does SpaceX plan to repair SLC-40?

On the prelaunch press conference about LC-39A Gwynne Shotwell (SpaceX COO) said that they plan on repairing the SLC-40 pad now, hoping to finish it in summer. Youtube: NASA Holds Pre-launch Briefing ...
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  • 5,038
10 votes

What holds the Space Shuttle orbiter itself stable on the launch pad?

The only hold-downs are the eight SRB bolts. This leads to the "Shuttle twang" when the main engines start. They're pushing to one side of the SRB hold downs, so they bend the stack just a bit. ...
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  • 12.3k
9 votes
Accepted

How does static test firing before launch affect design of rocket mass and structure?

Thrust to weight ration of boosters at takeoff needs to be greater than 1, else they do not go up. However, it is usually not greatly higher than 1. Usually 1.2-1.8 perhaps. This is obvious in ...
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  • 76.7k
9 votes
Accepted

What are/were the rails leading into the flame trench of pad 39A used for?

Those are remnants of the Apollo program era when the Launch Complex 39 was built. They were used to transport large removable blast deflectors to the pad when the Saturn V and Saturn 1B launch ...
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  • 75.6k
9 votes

How close can I get to a rocket launch and not get killed?

Keep in mind that a rocket engine is simply a controlled explosion. The explosion is directed at the ground, so most of the heat/flames/exhaust won't reach you unless you were very close. It would be ...
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  • 91
9 votes

What happens to the acoustic energy removed by a sound suppression system?

Yes, the water heats up. Lots of it evaporates. There is a system to catch and filter the remainder, which is polluted with combustion products of the SRBs. Those massive clouds in the foreground are ...
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  • 122k
9 votes
Accepted

Size of the new Starship Launch tower at Boca Chica?

The pier is just shy of 3 pickups in width as you can see in the photo below from RGV Aerial. The overall length of a Chevrolet Silverado pickup truck 4x2 double cab with 6.6-foot box is 231.8 inches. ...
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  • 653
9 votes

Were all three Mobile Launch Platforms ever in use simultaneously?

In August 1990, there were three shuttle stacks at least partially assembled on their MLPs at the same time: Columbia for STS-35, Atlantis for STS-38 and Discovery for STS-41. The picture in this ...
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