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First attempt of Starship test flight postponed

Frozen valve forces SpaceX to abort the launch; the company decided April 20 for next launch attempt.

B7 Rocket on deck with spacecraft Ship 24

The first flight test of SpaceX's Starship/SuperHeavy system was postponed today, April 17, due to a temperature problem in a valve in the first stage pressurization system. This would be the first flight of the Starship S24 spacecraft and the Super Heavy B7 rocket – the most powerful launch vehicle in the world, with 4,966 tons of mass and a capacity of 150 tons in Earth orbit. The countdown reached 5 minutes when it was announced that there was a problem with the valve and that the takeoff attempt would be converted into a full refueling test test (wet dress rehearsal or WDR), and then the rocket would be unloaded and recycled for the next occasion. .

In the final minutes of the countdown, the telemetry indicated the presence of condensed water that froze in the pressurization circuit of the first stage tanks; this in turn reached a return valve in the system, which jammed due to the low temperature.

The first stage is expected to separate from the second stage above Gulf of Mexico area and fall into the water near the coast, while the Starship will enter a fractional orbit. Shortly thereafter, the spacecraft will re-enter Earth's atmosphere and crash into the Pacific Ocean near Hawaii. The weather forecast shows moderate winds coming from the east, temperatures above 20°C and clear skies with high relative humidity.

Previously, Elon Musk, CEO of SpaceX, expressed some expressions about the launch:

“There is a high probability of delay, given the complexity of the rocket and the consequences of an error. We will be very careful with this release. If something goes wrong before launch, then a lot will go wrong afterwards…” “What is the measure of success in the first Starship launch? Don't blow up the launch pad!” “Most likely, the first launch will not be successful. If that means going into orbit.” “The rocket has 33 engines, and if even one of them fails, it will look like a box of grenades, very large grenades!”

Musk went on to describe how SpaceX views the rocket's complexity: “We assembled the entire rocket (superheavy and spacecraft) with sensors. All suspected critical locations will be monitored. Any behavior of parameters suspected to be anomalous (jumps in pressure, temperature, electrical parameters) will lead to canceling the prelaunch preparation in manual mode and in critical places from our point of view they will automatically cancel the prelaunch cyclegram with subsequent analysis. After understanding the meaning of what happened, we will make the necessary changes to the pre-launch cyclegram (if necessary) and try to carefully approach the checkpoint repeatedly.”

Authorization for three test flights

The first three Starship/Super Heavy flights will launch from Boca Chica. As these first three flights are part of the initial development phase, the Starship and Super Heavy will land in the North Pacific Ocean and the Gulf of Mexico, respectively. On the first flight, the Super Heavy is expected to land intact and sink in the Gulf of Mexico, and the Starship is expected to land in the North Pacific Ocean. An explosive event is expected to occur when the spacecraft impacts the ocean's surface. The second and third flights will result in the Super Heavy landing intact and sinking in the Gulf of Mexico, and the Starship being destroyed after atmospheric re-entry with a debris field in the Pacific. Prior to launch, SpaceX will release balloons to measure weather data. The data, including wind speed, are needed to determine if it is safe to launch and land the vehicle. The balloons are made of latex with radiosondes attached. A radiosonde, usually the size of a half-gallon box, is attached to the balloon to measure and transmit atmospheric data to the launch operator.

The latex balloon normally has a launch diameter of approximately four feet. When a balloon is released, it rises to approximately 19–29 kilometers in the air and then explodes. The radiosonde and fragmented balloon pieces fall back to Earth and are not recovered. The radiosonde has no parachute and is expected to sink to the bottom of the ocean. After liftoff, the rocket quickly gains altitude and flies over the ocean. At some point below range, it reaches supersonic speeds (which generates a sonic boom) and launches out to achieve its intended orbital trajectory.

Depending on the rocket's orientation, it's possible for the sonic boom to intercept the Earth's surface. Given the altitude at which the rocket reaches supersonic speeds, most of the sonic footprint that reaches the surface is usually of small magnitude (one to two pounds per square foot [psf]), but there may be areas that experience a sonic boom of up to eight psf. The area exposed to the highest overpressure (up to eight psf) is much smaller than those experiencing lower overpressures. The intensity of the sonic boom, in terms of psf, is greatest under the flight path and progressively weakens with greater horizontal distance from the flight path.

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