Six years to the week since its inaugural launch, the liquid-fueled Antares rocket roared aloft from Pad 0A at the Mid-Atlantic Regional Spaceport (MARS) on Wallops Island, Va., earlier today (Wednesday, 17 April), to deliver the next Cygnus cargo ship to the International Space Station (ISS). Flying for the tenth time (though only its ninth fully successful launch), Antares rose from the pad on time at 4:46 p.m. EDT, right at the start of a five-minute “window”, and current expectations are that Northrop Grumman’s NG-11 Cygnus spacecraft—named in honor of Apollo 1 hero Roger Chaffee—and its load of 7,600 pounds (3,450 kg) of equipment, experiments and supplies for the Expedition 59 crew will reach and berth at the space station early Friday morning.
First conceived by Orbital Sciences Corp. as its first large, liquid-fueled launch vehicle, Antares flew its “A-ONE” test mission on 21 April 2013, before successfully lofting three Cygnus cargo ships to the ISS between September 2013 and July 2014. However, a catastrophic failure, seconds after liftoff in October 2014 forced a lengthy period of grounding and by the time it returned to flight in October 2016 an already-in-the-works plan to replace its Aerojet Rocketdyne AJ-26 first-stage engine suite with Russian-heritage RD-181 engines had been completed. Since October 2016, and including tonight’s flight of NG-11, five Cygnus missions have flown atop uprated Antares 230 boosters.
As outlined in AmericaSpace’s NG-11 preview article, the initial cargo load aboard Cygnus was completed late last week, ahead of encapsulation in the Antares payload shroud and rollout of the 133-foot-tall (40.5-meter) booster to Pad 0A on Monday. However, for the first time on this mission, Northrop Grumman trialed a “late-load” capability to put cargo aboard the spacecraft within 24 hours of launch. Yesterday, following the mating of all rocket connections, save the liquid oxygen loading line, Antares was rotated from the vertical back into a horizontal orientation and a mobile payload processing facility was sealed over the fairing to provide a clean-room environment. Antares’ specialized removable nose cone—nicknamed the “pop-top”—was removed to allow technicians access to Cygnus. When the late-loading was completed, Antares was returned to the vertical. In the meantime, Launch Readiness Review (LRR) operations were finalized late Tuesday night.
Late-load functionality is expected to prove useful for time-sensitive payloads, including a 20-strong batch of live mice heading to the ISS on tonight’s mission. Part of the Rodent Research (RR)-12 investigation, provided by NASA’s Mountain View, Calif.-headquartered Ames Research Center (ARC), this experiment seeks to study their immune-system response to tetanus vaccinations. It is expected that RR-12 will test the hypothesis that exposure to spaceflight can decrease primary and secondary antibody responses to the challenge of an antigen; in this case, the tetanus vaccine. Researchers expect that RR-12 results may uncover new ways of improving vaccines and therapies for humans on Earth and in space.
Other payloads aboard Cygnus include the Advanced Colloids Experiment with Temperature Control (ACE-10T), provided by NASA’s Glenn Research Center (GRC) in Cleveland, Ohio. It will investigate methods to monitor and anticipate the possible failure of materials, slowing heating a fluid with colloidal particles in the Light Microscopy Module (LMM), in an effort which may also carry profound lessons for the predictions of terrestrial earthquakes. NASA’s Kennedy Space Center (KSC) has also supplied Veg-PONDS-02, a passive orbital nutrient delivery system to grow larger, longer-duration-growth plants in the station’s Veggie hardware. The PONDS hardware contains granular media for root-growth and a water reservoir and the experiment forms part of a much wider series of investigations to satisfy future requirements for fresh food to supplement crew diet.
Elsewhere aboard Cygnus is Canada’s Bio-Analyzer for detecting and quantifying cell-surface molecules on a per-cell basis, including blood-cell counts, and assesses soluble molecule concentrations in liquid specimens, such as blood, saliva or urine. By requiring just a few drops of liquid (a mere finger-prick, rather than an all-up blood-draw), Bio-Analyzer eliminates the need to freeze and store many biological samples. It is expected that this instrument will do for cellular and molecular biology what other tools aboard the ISS have done for general health and life sciences research. The cube-shaped, free-flying “Astrobee” will aid the station crew with routine chores, operating wholly autonomously or under remote control from the ground. Its cameras and sensors will allow for crew monitoring, sampling activities, logistics management and other tasks.
Weather conditions for Wednesday’s opening launch attempt were predicted to be highly favorable, improving steadily from 85-percent to around 95-percent probability of acceptable conditions at T-0. “An area of high pressure will press down from the Northeast states Wednesday morning, forcing a backdoor cold front through the Wallops Region to shift surface winds out to a northeasterly component for the launch window,” noted Wallops’ L-2 weather briefing on Monday. “A weak upper-level disturbance within the northwesterly upper-level flow will track towards the Mid-Atlantic Wednesday to increase upper-level cloudiness.” All told, the potential violating factors centered upon a small chance of excessive ground winds and thick clouds. By launch day, however, conditions improved substantially to 100-percent favorable.
Emblazoned with the Northrop Grumman livery—as was its predecessor, the NG-10 Cygnus mission, launched last November—Antares was confirmed vertical on Pad 0A in the small hours of Wednesday morning. Launch operations got underway shortly thereafter, when engineers and flight controllers came to their consoles at Wallops to begin powering-up rocket systems and chilling propellant lines with liquid nitrogen. Tanking was critically timed about 90 minutes before T-0, due to temporal limits associated with the rapid boil-off of the cryogens.
A final poll of flight controllers occurred in two phases and by T-15 minutes all of Antares’ propellant tanks attained flight pressures and were verified “Flight-Ready”. Shortly afterwards, the booster transferred to Internal Power and at the Transporter-Erector-Launcher (TEL)—which provides Antares with a supporting/retaining strongback on Pad 0A—was armed, allowing it to effect a rapid retraction shortly before T-0.
All in all, countdown operations proceeded smoothly, although a Red Team was despatched to the pad for a short time to attend to an issue with the TEL.
“Range is Green,” came the call at T-3 minutes and 45 seconds, as Antares flexed its muscles for launch.
At 4:46 p.m. EDT, the two RD-181 engines at the base of the rocket thundered to life and quickly ramped up to a combined thrust of 937,000 pounds (425,000 kg). A second-and-a-half later, after computer-commanded health checks, Antares was released from the pad and began a fast climb into the late-afternoon Virginia sky, pitching and rolling onto the correct flight azimuth to insert its payload into a 51.6-degree orbit. All told, the RD-181 engines burned for 3.5 minutes, before shutting down on time.
Antares’ first stage was then jettisoned and the solid-fueled Castor-XL upper stage ignited to push the NG-11 Cygnus into an orbital “slot”, some 195 miles (315 km) above Earth. Less than ten minutes had elapsed since departing MARS.
Seventy minutes after launch, Cygnus’ twin fan-shaped solar arrays had been deployed, ready for a personal-best-beating day-and-a-half chasedown of the space station. Current plans are for the cargo ship to arrive in the ISS vicinity early Friday morning and be robotically captured by the 57.7-foot-long (17.6-meter) Canadarm2—operated by Expedition 59 astronauts Anne McClain and David Saint-Jacques—about 5:30 a.m. EDT. Coming a mere 37 hours after launch, this is significantly shorter than previous Cygnus missions, which typically followed a rendezvous profile lasting anywhere from 46 hours to several days.
Ground controllers will then rotate the Cygnus to its berthing location on the Earth-facing (or “nadir”) port of the Unity node. It is expected to remain attached to the station until 23 July, setting a new record of 95 berthed days for a Cygnus, before it is detached for a period of autonomous free-flight, ahead of destructive re-entry later in the year.