The Atlas V rocket at complex 41 at Cape Canaveral in Florida, USA, is already counting down to launch a mission involving United Launch Alliance (ULA), NASA, and Orbital ATK as part of the US commercial space initiatives.

The Cygnus spacecraft, named after former USA astronaut John Glenn, took off atop a United Launch Alliance (ULA) Atlas V rocket at 11:11 a.m. EDT (1511 GMT) from Cape Canaveral Air Force Station in Florida.

"We are looking forward to a great launch tomorrow and continuing our record of 100 percent mission success", Vern Thorp, United Launch Alliance's (ULA) commercial missions program manager, told reporters during a briefing Monday (April 17).

Large launch vehicles stand ready in three major space-faring nations on Tuesday ahead of missions to variously send astronauts and supplies to destinations in low Earth orbit. Preliminary results from a study of astronaut twins, however, show the telomeres of former astronaut Scott Kelly, who spent almost a year aboard the station in 2015 and 2016, actually lengthened during his time in orbit, the opposite of what was expected. The Antares was grounded for two years after that while the vehicle's engines were replaced; the Atlas V served as a stopgap in the meantime so that Orbital could continue to resupply the station as part of its contractual obligations to NASA.

The mission's OA-7 Cygnus capsule was named after former astronaut John Glenn, the first man to orbit Earth. At a total weight of approximately 15,928 pounds, OA-7 will include approximately 7,452pounds of internal cargo and an 183 pounds of external deployer carrying CubeSats. That is about 660 lbs. The seventh Cygnus is set to launch April 18 from Cape Canaveral Air Force Station in Florida. In addition, NASA launched an Advanced Plant Habitat for plant-growth studies to be carried out on the ISS. The first science experiments are planned for November. These conjugates combine an immune-activating drug with antibodies and target only cancer cells, which could potentially increase the effectiveness of chemotherapy and reduce side-effects.

The capsule also carries 38 shoebox-sized satellites and a high school student's science project that will test how telomeres, which are structures at the ends of chromosomes, are affected by microgravity. Weather appears favorable for a launch. The OA-7 mission has been on hold for a month due to a technical issue with the rocket's first-stage hydraulics.