NASA plans to replace an engine controller aboard its massive SLS rocket after finding a communications glitch with the system's avionics during preflight testing, the latest setback in a program for which Boeing Co. is the main contractor and that has been plagued by years of delays and billions of dollars in costs beyond its initial budget.

The National Aeronautics and Space Administration also said Friday it will explore launch dates for a test flight in March and April.

The rocket, which Congress authorized and began funding in 2010, was supposed to fly in late 2016. In October, NASA solicited ideas from the aerospace industry about ways to lower the costs associated with the Space Launch System.

Replacing the unit on one of the SLS's four RS-25 engines is "the best course of action," the agency said. The update comes after engineers preparing the rocket for flight detected a communications problem last month between the rocket's avionics system and the No. 4 engine, and began troubleshooting the issue.

NASA plans to use the Space Launch System rocket and Orion crew capsule to return astronauts to the moon later this decade.

In science fiction stories about contact with extraterrestrial civilisations, there is a problem: What kind of propulsion system could make it possible to bridge the enormous distances between the stars? It cannot be done with ordinary rockets like those used to travel to the moon or Mars. Many more or less speculative ideas about this have been put forward—one of them is the "Bussard collector" or "Ramjet propulsion". It involves capturing protons in interstellar space and then using them for a nuclear fusion reactor.

Peter Schattschneider, physicist and science fiction author, has now analyzed this concept in more detail together with his colleague Albert Jackson from the USA. The result is unfortunately disappointing for fans of interstellar travel: it cannot work the way Robert Bussard, the inventor of this propulsion system, thought it up in 1960. The analysis has now been published in the scientific journal Acta Astronautica.

The hydrogen-collecting machine

"The idea is definitely worth investigating," says Prof. Peter Schattschneider. "In interstellar space there is highly diluted gas, mainly hydrogen—about one atom per cubic centimeter.

With many countries, companies and individuals intensifying their space exploration programs, questions about rights, ownership and the feasibility of manned space missions are coming to the fore of public debate.

In early 1610, Italian astronomer and physicist Galileo Galilei wrote a letter to Cosimo de' Medici—then Grand Duke of Tuscany—stating that he had observed for moons of Jupiter (which Galileo initially believed to be stars) using his improved telescope lens. Hoping to secure the grand duke's patronage, Galileo proposed naming the bodies after Cosimo's family, eventually calling them the "Medicea Sidera," or the Medicean stars. (In the end, the moons were named for four lovers of the god Zeus: Io, Europa, Ganymede and Callisto.)

Galileo was not the first to claim stars in the name of people on Earth, and he was to be far from the last. Although the names of celestial bodies are now determined by the International Astronomical Union using a systematic naming system, the idea that outer space is terra incognita, a place yet unexplored or claimed, where everything is up for grabs, is more powerful today than ever before.

When the immense sound of the Ariane 5 rocket rumbles across Europe's spaceport in French Guiana, it will signal the end of a journey decades in the making. Perched atop the rocket will be the James Webb Space Telescope (JWST), the most sophisticated and complex observatory ever constructed. An enormous mirror 6.5 meters across, consisting of 18 gold-plated segments, will be delicately folded to fit within the nose cone.

That precious cargo carries the hopes and dreams of thousands of engineers and scientists like us who have worked for so long to make this observatory a reality. We'll no doubt all be holding our breath.

If all goes well, humanity will have a new eye on the cosmos, with capabilities that far surpass anything that has gone before.