Displayed for years in a Kennedy Space Center booth, a letter-to-the-newspaper editor is filing a complaint that has made NASA's Launch Services Program employees laugh.

"They were upset that they were still awakened by the launches, and wanted to know why NASA did not know how to get into the day," said Brian Beaver, head of the flight dynamics branch of the program. "Why do I get woken up by rockets in the middle of the night?"

The inhabitants of Space Coast may be wondering the same thing this summer after a series of NASA bombings and trade missions.

The next launch, a SpaceX commercial satellite mission targeted for Sunday 11:28 pm, continues the trend as the sixth consecutive takeoff of Cape Canaveral to fall between the hours of 11 pm. and at 6 am, when most people are more concerned with deep sleep than with deep space.

But the letter writer and other light sleepers can rest assured, said Beaver, that if launch teams could choose more practical day launch windows, they would do it.

"We do not like to get up in the middle of the night either," he said. "If someone starts in the middle of the night, there is usually a very specific reason."

The reasons for this summer have varied, for missions ranging from an International Space Station freight station to a solar science probe, to commercial satellites above the equator.

Each type of mission has different restrictions that determine their launch windows, and it seems like it's a coincidence that so many rows ended up on the graveyard dock.

"The answer is simple, it's just that it works," said Beaver, whose office has played a role in two of the recent launches.

For SpaceX's June 29 launch of a Dragon cargo capsule at the NASA space station, there was only one hour of the day when the plane from the station's orbit was crossing the launch site – at 5:42 am.

A Falcon 9 rocket had to set sail at that time to place the Dragon on a northeast course that could track the lab complex into orbit for a rendezvous three days later.

If the mission did not fly at that moment, she should have tried again the next day, even earlier.

"To meet something that is not beyond the equator, you have a very small launch window because the launch site has to go under the orbit with which you are going." says Marshall Kaplan of Launchspace Services. cabinet based in Bethesda, Maryland. "It gets complicated quite quickly."

All those who got up early to see this launch were rewarded with one of the most beautiful flights of the year, as the first rays of sun attracted the flare of the rocket with stunning visual effects.

On August 12, the United Launch Alliance's Delta IV Heavy rocket was launched at 3:31 am with NASA's Parker Solar probe.

The path from the probe to the sun depended on an overflight of Venus, a trajectory that could only be reached about an hour a day over a period of three weeks. Otherwise, the planetary alignments would be disabled.

The result: a pre-dawn launch by one of the world's most powerful rockets, whose sound probably rattled more than a few dormant residents.

Like the planned launch of the Telstar 18 Vantage mission on Sunday, several of the recent missions have involved boosting commercial communications satellites in orbit 22,300 miles above the equator.

In these "geostationary" orbits, the satellites correspond to the speed of rotation of the Earth and thus appear from the ground hovering in fixed points of the sky.

The destination can be reached at any time of the day, so why kill them in the early morning?

It turns out that the position of the sun – not at the moment of launch, but when the satellite separates from the rocket in orbit – is the determining factor.

Engineers want the solar panels of the spacecraft to be sun-bathed as soon as they are deployed, so that they start producing electricity and the spaceship becomes "powerful" rather than continue to drain the charged batteries before launching.

The separation of the satellite from the rocket about 33 minutes after takeoff is just the beginning of the journey to its final orbit, which must be raised and circularized around the equator. This process could take days or more.

"If the sun shines on the wrong side of the spacecraft when it does, it can not charge its batteries," Kaplan said.

Launch windows for communication satellites can last several hours, providing much more flexibility than an instant space station window or limited planetary opportunities. But aligning the correct sun angle may require a launch during the night.

For these missions, it is possible that several hours of the day can work.

Weather and other factors, such as range availability, can become considerations.

The recent wave of late launches is characterized by lower probabilities of thunderstorms during Florida's afternoons and summer evenings.

"In the summer, here in Florida, it's very hard at 3:33 pm, and 3:33 in the morning," said Kathy Rice of the 45th Air Force Squadron, before the first attempt to launch the solar probe. "We expect to see these afternoon thunderstorms every day, but as the day progresses and we enter the evening, they will dissipate."

Calculations defining launch windows can be much more complex for some missions.

For example, while engineers want sunlight to hit the solar panels of a satellite at the right time, they may want cameras, sensors, or instruments in the shelter of light and heat at least until they can control their cooling or get away from the sun.

A sensitive period during launches is often the long coast in a low "parking" orbit between engine burns from the upper stage of the rocket. The launch time must take into account the effects of the sun throughout the flight.

"You're trying to balance a set of launch-related constraints, so you're very quickly at a certain time of day," Beaver said.

Ground conditions can determine when a long window ends. The super-cold fuel or the oxidant of a rocket, which declines throughout a countdown, can only be replenished if the tanks are to be emptied for a later attempt. Engineers can only stay in console for a long time before having to rest.

The end of the summer will not mean the end of the night launches.

Two missions planned for October have windows open at 4 am and around midnight.

The first includes an air launch rocket that will be launched at altitude over the ocean, an event that will allow NASA's Launch Services program to team up all night long but should not disrupt coasters.

Before that, another NASA science mission will leave California before sunrise, local time.

"It's hard for everyone," Beaver said. "There is a way to avoid, we will, frankly. It's usually because it's the only way to do the mission. "

Contact Dean at 321-917-4534 or [email protected]. And follow us on Twitter at @flatoday_jdean and on Facebook at https://www.facebook.com/FlameTrench.

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Launching Sunday

• Rocket: SpaceX Falcon 9 (Block 5, new)
• Mission: Telesat Telstar 18 Vantage Communication Satellite
• Launch time: 23h28
• Launch window: Four o'clock, until 3:28 am Monday
• Launching Complex: 40 at the Cape Canaveral Air Base
• Weather: 60%

Join floridatoday.com for countdown and chat updates from 10:30 pm. Sunday, including the broadcast of the SpaceX launch webcast about 15 minutes before takeoff.

Late launches

• June 4, 12:45 pm: Launch of SES-12 communications satellite by SpaceX
• June 29, 5:42: SpaceX launches CRS-15 cargo mission to ISS for NASA
• July 22, 1:50 pm: Launch of the Telstar 19 Vantage communication satellite by SpaceX
• August 7, 1:15 pm: Launch of the Merah Putih communications satellite by SpaceX
• August 12, 3:31 pm: United Launch Alliance launches NASA's Parker solar probe
• September 9, 23:28: SpaceX aims to launch Telstar 18 Vantage communication satellite

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