Following a 24-hour postponement, due to predicted unfavorable downrange weather, Dragon Endeavour took flight a second time at 5:49 a.m. EDT Friday and is now well underway in her day-long chasedown of the International Space Station (ISS).
Current plans are for the sturdy craft and her four-member crew—Commander Shane Kimbrough and Pilot Megan McArthur of NASA, together with Mission Specialists Aki Hoshide of the Japan Aerospace Exploration Agency (JAXA) and Frenchman Thomas Pesquet of the European Space Agency (ESA)—to dock at International Docking Adapter (IDA)-2 on the forward-facing end of the station’s Harmony node at 5:10 a.m. EDT Saturday.
With this morning’s perfect launch, Dragon Endeavour becomes the first human-carrying, orbital-class space vehicle since the Space Shuttle era to fly more than once.
Although the weather outlook for Crew-2’s originally targeted Thursday launch was around 80-percent favorable, with a slight risk posed by Liftoff Winds, NASA and SpaceX elected to postpone to Friday, where conditions were expected to improve to 90 percent. In a Countdown Clock briefing on Wednesday, KSC Director Bob Cabana noted that “downrange winds and wave-heights” posed an added risk in terms of executing a safe launch abort should one become necessary.
“Although conditions around the launch site were expected to be favorable for liftoff, mission teams also must consider conditions along the flight path and recovery area in the unlikely event of a launch escape,” NASA noted in a Wednesday update. “For a launch April 23, the U.S. Space Force’s 45th Weather Squadron predicts a 90-percent chance of favorable weather conditions at the launch pad for liftoff of the Crew-2 mission, based on Falcon 9 Crew Dragon launch weather criteria. Conditions also are expected to improve along the flight path and recovery area for the mission.” Principal concerns remained Liftoff Winds.
For Dragon Endeavour herself, it has a remarkable year. Contracts to build the vehicle were awarded by NASA to SpaceX way back in November 2015, with an expectation that she would that she would go on to fly the Crew-1 mission, originally known as the first Post-Certification Mission (PCM-1). However, following the uncrewed Demo-1 flight in March 2019 and its subsequent loss during a test-stand explosion in April 2019, the vehicle manifest was realigned.
As a consequence, the Crew Dragon originally assigned to the crewed Demo-2 mission—the next available vehicle off the SpaceX production line—was pressed into service for an In-Flight Abort Test in January 2020 and the vehicle originally assigned to Crew-1 became “Dragon Endeavour” and wound up launching NASA astronauts Doug Hurley and Bob Behnken to the space station last 30 May.
As such, Dragon Endeavour—which Hurley and Behnken named in honor of the first Space Shuttle they flew in their astronaut careers—becomes the first crew-carrying, orbital-class space vehicle to launch more than once in almost a full decade. Not since the final voyage of Atlantis on STS-135 in July 2011 has such a feat of reusability been achieved.
Following her return from the 64-day Demo-2 mission last August, Dragon Endeavour was put directly into processing for her next flight. A decision that she would likely fly Crew-2 was made whilst she was in orbit and she has undergone several enhancements, primarily focused on abort safety, ahead of this second mission. Last month, NASA Commercial Crew Program Manager Steve Stich noted that Endeavour carries “enhanced capabilities” to handle rougher seas and stronger winds during splashdown.
“One of the upgrades on this vehicle is improved pad-abort performance,” Mr. Stich explained. “The Dragon is designed to have continuous abort capability from the launch all the way until it gets into orbit. SpaceX went off and looked at a way to optimize their propellant system and provide a little more propellant for an abort off the pad.” He added that this process enabled an improvement in the ship’s flight-safety envelope in a pad-abort situation, as well as an improvement in launch availability, thanks to the capacity to handle “a little bit stronger onshore winds”.
Elsewhere, Dragon Endeavour benefits from a strengthened outer structure to handle the rough seas; specifically, this aims to reduce impacts from “secondary splash”, as water hits the spacecraft immediately after it reaches the ocean. Modifications were also made to the propulsion system, including enhancements to her SuperDraco thrusters and a transition in some components from titanium and stainless steel.
“I really look at this flight as kind of an abort-enhancement flight,” Mr. Stich explained. “If you step back and look at this flight, we are improving the risk posture to the vehicle by improving aborts, improving the pad-abort capability, eliminating titanium in the propulsion system, improving downrange aborts by changing the software. We’re continuing to endeavor to buy-down risk in the program over time.”
Not only was Dragon Endeavour flying again, but so too was the “B1061” Falcon 9 core, which previously saw service to lift Crew-1 astronauts Mike Hopkins, Victor Glover, Shannon Walker and Soichi Noguchi to the station last November. This morning it therefore became the 26th Falcon 9 core to satisfactorily complete a second mission since March 2017. The booster was rolled out to historic Pad 39A at the Kennedy Space Center (KSC) in Florida last week and performed a customary Static Fire Test of its nine Merlin 1D+ first-stage engines on Sunday.
Following a one-day postponement from Thursday, the four astronauts were awakened in their quarters in the Neil Armstrong Operations & Checkout Building around 11 p.m. EDT Thursday. They breakfasted and proceeded to the suit-room, where they were helped into their customized black-and-white SpaceX launch and entry suits, before departing for their ride to the pad in Tesla Model Xs shortly after 2:30 a.m. EDT Friday.
After a 25-minute journey to Pad 39A—assisted by Astronaut Support Person (ASP) and seasoned ISS veteran Jessica Meir—they began boarding Dragon Endeavour and pressed directly into communications and suit integrity checks.
B1061 lit up the pre-dawn sky with a spectacular 5:49 a.m. EDT launch, an hour before local sunrise. After boosting the 230-foot-tall (70-meter) rocket uphill for 2.5 minutes, the nine Merlins shut down on time and B1061 separated from the stack and returned smoothly to land on the deck of the Autonomous Spaceport Drone Ship (ASDS), “Of Course I Still Love You”. Meanwhile, the Merlin 1D+ Vacuum engine of the Falcon 9’s upper stage ignited to push Dragon Endeavour smoothly into low-Earth orbit.
Kimbrough, McArthur, Hoshide and Pesquet are now well into their 24-hour and 16-orbit rendezvous profile to reach the ISS at about 5:10 a.m. EDT Saturday. In addition to the astronauts, Dragon Endeavour also carries a total of 543.2 pounds (246.4 kg) of pressurized internal cargo. This includes 165 pounds (74.9 kg) of Utilization hardware, 49.6 pounds (22.5 kg) of Crew Supplies, 70.8 pounds (32.1 kg) of Extravehicular Activity (EVA) gear, 71.6 pounds (32.5 kg) of Vehicle equipment, 1.5 pounds (0.7 kg) of computer resources and 184.5 pounds (83.7 kg) of NASA-provided supplies.
Following tomorrow’s docking, the hatches into the station will be opened about 7:15 a.m. EDT and the newcomers will be greeted by incumbent Expedition 65 Commander Shannon Walker and her crew of fellow NASA astronauts Mike Hopkins, Victor Glover and Mark Vande Hei, Japan’s Soichi Noguchi and Russian cosmonauts Oleg Novitsky and Pyotr Dubrov. This will create a rare occurrence of two Japanese crew members aboard the ISS simultaneously.
Although this has happened before—back in April 2010, Noguchi was aboard as part of the Expedition 23 crew when Naoko Yamazaki arrived for a short stay on shuttle Discovery—it will be the first time that a pair of long-duration Japanese crew members have crossed over on the station. Furthermore, with 11 crew members aboard for the last few days of April, the ISS will boast its largest human population since the departure of shuttle Endeavour on STS-134 in May 2011.