Favorable weather outlook for Friday’s twilight Delta 4 launch from Florida

The Delta 4 will launch from Complex 37. Credit: ULA

CAPE CANAVERAL — Air Force meteorologists are expecting good weather to launch the Delta 4 rocket with a military communications satellite when the sun goes down Friday evening at Cape Canaveral.

Liftoff of the United Launch Alliance booster carrying the Wideband Global SATCOM 9 spacecraft for the U.S. Air Force is scheduled to occur at 7:44 p.m. EST (2344 GMT). The launch window will remain open for 74 minutes to 8:58 p.m. (0058 GMT).

The chances of allowable weather stand at 90 percent, with only a slight concern for liftoff winds during the launch opportunity.

“A high pressure area will gradually move into the Southeast U.S. Thursday and Friday, and as this occurs, the pressure gradient will slacken and winds will decrease,” forecasters at the 45th Weather Squadron say.

“Weather is generally favorable for launch.”

The launch time conditions are expected to include only scattered clouds, good visibility, ground winds from the east at 10 gusting to 15 knots, a relative humidity of 67 percent and a temperature of 63 degrees F.

Saturday’s backup launch window, if needed, should have 80 percent favorable weather, forecasters say.

An on-time liftoff at the opening of the window would occur 12 minutes after sunset but well within twilight conditions.

The closest free public viewing location is along Route 401 in Port Canaveral, some 8.6 miles from the launch pad, according to LaunchPhotography.com.

The WGS 9 spacecraft is an international contribution to the U.S. military’s highest-capacity, worldwide communications satellite constellation. Canada, Denmark, the Netherlands, Luxembourg and New Zealand funded construction of this satellite in exchange to bandwidth from the entire global network.

The Boeing-built WGS network provides high-volume communications anytime, anywhere to soldiers, ships, aircraft and drones.

The final closeouts of vehicle compartments are underway ahead of the Launch Readiness Review on Tuesday and the countdown starting Wednesday morning.

Here’s a look at some stats about the mission. This will be:

  • The 377th Delta rocket launch since 1960
  • The 35th Delta 4 rocket mission since 2002
  • The 7th Medium+ (5,4) configuration to fly
  • The 53rd main engine from RS-68 family used
  • The 11th RS-68A main engine flown
  • The 56th-57th-58th-59th GEM-60 solid rocket motors flown
  • The 479th production RL10 engine to be launched
  • The 38th RL10B-2 engine launched
  • The 29th Delta 4 rocket launch from Cape Canaveral
  • The 37th launch from Pad B at Complex 37
  • The 20th use of Delta 4 by the Air Force
  • The 105th Evolved Expendable Launch Vehicle flight
  • The 118th United Launch Alliance mission since 2006
  • The 85th ULA launch from Cape Canaveral
  • The 47th ULA launch for the Air Force
  • The 28th Delta 4 under the ULA banner
  • The 3rd ULA launch this year
  • The 1st launch of the Delta family in 2017
  • The 9th Wideband Global SATCOM satellite
  • The 3rd Block 2-Follow On WGS satellite
  • The 7th WGS on Delta 4

See earlier WGS 9 coverage.

Our Delta archive.