The Parker Solar Probe countdown is underway toward a liftoff at 3:31 a.m. EDT. During the last four minutes of the countdown, the Delta IV Heavy propellant tanks will be brought up to flight pressure, the rocket and spacecraft will be confirmed on internal power, and the Eastern Range and launch managers will perform final status checks. A computerized autosequencer will take over the countdown in order to conduct a host of activities in precise order.
T-4 Minutes and Holding
The launch countdown is in a T-4 minute hold. The launch team is proceeding toward launch of a United Launch Alliance Delta IV Heady rocket carrying Parker Solar Probe on a mission to the Sun.
Liftoff is scheduled for 3:31 a.m. EDT, at the beginning of a 65-minute launch window. The forecast is now at 95 percent chance for favorable weather conditions for launch.
Parker Solar Probe Named for Physicist

In 2017, the mission was renamed for Eugene Parker, the S Chandrasekhar Distinguished Service Professor Emeritus, Department of Astronomy and Astrophysics at the University of Chicago. In the 1950s, Parker proposed a number of concepts about how stars–including our Sun–give off energy. He called this cascade of energy the solar wind, and he described an entire complex system of plasmas, magnetic fields, and energetic particles that make up this phenomenon. Parker also theorized an explanation for the superheated solar atmosphere, the corona, which is –contrary to what was expected by physics laws–hotter than the surface of the Sun itself. This is the first NASA mission that has been named for a living individual.
Parker Solar Probe Countdown to T-Zero
The United Launch Alliance Delta IV Heavy rocket reached another major milestone on the road to T-Zero, as NASA’s Parker Solar Probe is prepared for launch. Stacking the rocket begins with three boosters – the largest components – and continues with the addition of a second stage. A third stage is added to help give NASA’s Parker Solar Probe the extra boost needed to send it far into space and on its way to the Sun. Parker Solar Probe is scheduled to lift off atop the Delta IV Heavy at 3:31 a.m. EDT, at the beginning of a 65-minute launch window, on Aug. 12, from Space Launch Complex 37 at Cape Canaveral Air Force Station in Florida. View the Countdown to T-Zero video at https://youtu.be/JSgNtjoOc4Y.
NASA’s Parker Solar Probe Ready to Launch Aboard ULA Delta IV Heavy Rocket

Good morning from NASA’s Kennedy Space Center in Florida. All is ready for launch of a United Launch Alliance Delta IV Heavy rocket carrying NASA’s Parker Solar Probe. Liftoff is scheduled for 3:31 a.m. EDT from Space Launch Complex 37 at Cape Canaveral Air Force Station. The Delta IV will launch NASA’s Parker Solar Probe on its journey to the Sun, venturing closer than any spacecraft before it. Launch countdown activities continue for this morning’s launch attempt. The weather forecast for today’s launch is now at 95 percent chance for favorable weather at liftoff.
The launch blog originates from the NASA News Center here at Kennedy, a few miles west of the launch complex. There’s more to come, so stay with us.
Follow televised coverage of the launch countdown and launch at https://www.nasa.gov/nasalive.
NASA’s Parker Solar Probe Ready for Launch Atop Delta IV Heavy Rocket
Hello, and welcome back to our coverage of the Parker Solar Probe launch. Everything is proceeding toward launch of the pioneering spacecraft at 3:31 a.m. EDT on a United Launch Alliance Delta IV Heavy rocket from Space Launch Complex 37 at Cape Canaveral Air Force Station in Florida.
The weather forecast has improved to 95 percent chance for favorable weather at liftoff. Stay tuned, launch coverage will begin at 3 a.m.
Parker Solar Probe New Launch Date is Aug. 12
The launch of a United Launch Alliance Delta IV Heavy rocket carrying the Parker Solar Probe spacecraft was scrubbed today due to a violation of a launch limit, resulting in a hold. There was not enough time remaining in the window to recycle.
The launch is planned for Sunday, Aug. 12 from Space Launch Complex-37 at Cape Canaveral Air Force Station. The forecast shows a 60 percent chance of favorable weather conditions for launch. The launch time is 3:31 a.m. EDT.
T-4 Minutes and Counting
The Parker Solar Probe countdown is underway toward a liftoff at 4:28 a.m. EDT. During the last four minutes of the countdown, the Delta IV Heavy propellant tanks will be brought up to flight pressure, the rocket and spacecraft will be confirmed on internal power, and the Eastern Range and launch managers will perform final status checks. A computerized autosequencer will take over the countdown in order to conduct a host of activities in precise order.
T-4 Minutes and Holding
The launch countdown is in a T-4 minute hold. The launch team is proceeding toward launch of a United Launch Alliance Delta IV Heavy rocket carrying Parker Solar Probe on a mission to the Sun.
Liftoff is now scheduled for 4:28 a.m. EDT with a 95 percent chance for favorable weather.
Workhorse Rocket to Carry NASA’s Parker Solar Probe
The rocket standing on the pad at Space Launch Complex 37 is a United Launch Alliance Delta IV Heavy configuration. The 233-foot-tall rocket is the world’s second highest-capacity rocket and most powerful rocket currently used by NASA. The launch vehicle consists of three Common Booster Cores, each with an RS-68A engine. Each engine produces 702,000 pounds of thrust for a combined total liftoff thrust of more than 2.1 million pounds.
A cryogenic second stage, powered by an RL10 engine, is on the center core. It is fueled by liquid hydrogen and liquid oxygen. The boosters are controlled by the second stage avionics system, which provides guidance, flight control and vehicle sequencing functions during the booster phases of flight.
For the first time ever, a solid fuel third stage, provided by Northrup Grumman, is part of the Delta IV Heavy rocket’s configuration. It is attached to the Parker Solar Probe and will help boost the spacecraft into the proper trajectory for its mission.
The Parker Solar Probe was moved from nearby Astrotech Space Operations in Titusville to Launch Complex 37 on July 30. The spacecraft was lifted and attached to the top of the Delta IV Heavy rocket in the Vertical Integration Facility. Parker Solar Probe will be the fastest human-made object in the solar system, traveling at speeds of up to 430,000 miles per hour (700,000 kilometers per hour).
This Delta IV Heavy will carry the Parker Solar Probe, humanity’s first mission to the Sun’s corona, on its journey to explore the Sun’s atmosphere and the solar wind. Launch is scheduled for 3:53 a.m. EDT.