Artists concept of SpaceXs Red Dragon spacecraft. Credit: SpaceX

SpaceXs upgraded Dragon capsules will not return astronauts to Earth for powered landings as originally envisioned, company boss Elon Musk said Wednesday, a design change that raises questions about the space transport firms plans to send commercial landers to the surface of Mars.

Musk cited safety concerns for eliminating plans for propulsive Dragon landings in remarks at the International Space Station Research and Development Conference in Washington. He also said the original Dragon landing concept, in which four landing legs would extend from the base of the capsules heat shield as throttleable SuperDraco thrusters slowed the crafts speed for touchdown, was not as useful as he initially thought for SpaceXs plans to send humans to Mars.

That was a tough decision, Musk said in response to a question on the matter. He added that the human-rated Dragon, which SpaceX is developing with mostly NASA funding, is technically still capable of propulsive landings.

Although youd have to land it on some pretty soft landing pad because weve deleted the little legs that pop out of the heat shield, Musk said.

SpaceX unveiled the design of the next-generation spacecraft in May 2014, when Musk predicted the capsule should be ready to ferry astronauts to and from the International Space Station by the end of 2016. Musk said Wednesday that the spaceship is now scheduled to launch crews by mid-2018, and he described the crew capsule effort as SpaceXs primary focus.

NASA awarded SpaceX a $2.6 billion contract later in 2014 to finish development of the upgraded Dragon spacecraft called Crew Dragon or Dragon 2 and fly up to six crew rotation missions to the space station. Boeing won a similar contract worth $4.2 billion for its CST-100 Starliner spacecraft.

Both programs have been delayed and will miss NASAs goal of having the vehicles certified for piloted missions by the end of 2017, ending U.S. reliance on Russian Soyuz spacecraft to carry astronauts to the space station and return them to Earth.

Boeing says the CST-100 Starliners first orbital test flight with a two-person crew in August 2018.

SpaceX officials said in 2015 that the Crew Dragons first few missions would end with parachute-assisted splashdowns at sea, similar to the way the current Dragon cargo capsules come back to Earth. The crew-capable version is heavier, requiring four main chutes instead of the three flying on station resupply flights.

But engineers continued to plan for propulsive landings once NASA certified the powered descent approach. The Crew Dragon will already have the SuperDraco thrusters needed for a powered descent. The same rocket packs act as the capsules escape booster to whisk astronauts away from a failing launcher.

That is how a 21st century spaceship should land, Musk said in 2014, describing the crew capsules ability to land anywhere on Earth with the accuracy of a helicopter.

SpaceX now favors another type of recovery.

The reason we decided not to pursue (powered landings) heavily is it would have taken a tremendous amount of effort to qualify that for safety, particularly for crew transport, Musk said. And then there was a time when I thought that the Dragon approach to landing on Mars, where youve got a base heat shield and side-mounted thrusters, would be the right way to land on Mars, but now Im pretty confident that is not the right way, and that theres a far better approach.

Musk did not elaborate on the new concept for landing on Mars.

Thats what the next generation of SpaceX rockets and spacecraft is going to do, so just the difficulty of safely qualifying Dragon for propulsive landings, and the fact, from a technology evolution standpoint, it was no longer in line with what we were confident was the optimal way to land on Mars, Musk said. Thats why were not pursuing it.

It could be something that we bring back later, but it doesnt seem like the right way to apply resources right now.

The redesign of the next-generation Dragons landing system will affect SpaceXs plans to send the first in a series of robotic Dragon spacecraft to Mars in 2020. Musk did not address the status of the first so-called Red Dragon mission Wednesday, but the concept involved dispatching a Dragon capsule similar to the ship built for crews to the red planet on top of a huge Falcon Heavy booster.

The Red Dragon would have descended to a powered touchdown on landing legs in a sequence similar to the one envisioned for Crew Dragons on Earth.

Gwynne Shotwell, SpaceXs president and chief operating officer, said in February that the first Red Dragon flight was delayed to mid-2020 from 2018, pushing its arrival at Mars back to early 2021. Launch opportunities to Mars come approximately every 26 months when the planets are favorably aligned.

The Red Dragons would have delivered cargo and experiments to the Martian surface and tested supersonic retro-propulsion in the planets rarefied atmosphere for the first time. NASA engineers say a rocket-braking mechanism like the Dragons SuperDraco thrusters is needed to safely land heavy supply ships and crew vehicles on Mars.

The space agency signed up to support the privately-developed Red Dragon project to gather data on supersonic retro-propulsion officials said NASA would be unable to obtain until at least the late 2020s with a government-managed mission. NASA said it would spend more than $30 million on the effort by providing advisors, navigation, communications and tracking services, and technical analysis.

Musk wrote in a tweet that SpaceX has not abandoned supersonic retro-propulsion at Mars.

Plan is to do powered landings on Mars for sure, but with a vastly bigger ship, he tweeted Wednesday after his remarks in Washington.

Musk said his team at SpaceX is refining how the company could send people to Mars, eventually to settle there. He revealed a Mars transportation architecture in a speech at the 67th International Astronautical Congress in Guadalajara, Mexico, last year, but the outline has since changed.

A vision for gigantic interplanetary transporters Musk presented last year has been downsized, he said.

Its a little smaller, still big, but I think this ones got a shot at being real on the economic front, Musk said, adding that he might present more details at this years International Astronautical Congress in Adelaide, Australia.

Musk said SpaceX is making progress on the Crew Dragon vehicle, which has a different aerodynamic shape than the companys cargo craft. Designers are also adding a life support system, seats, cockpit displays and other equipment for human passengers.

Its been way more difficult than cargo, for sure, Musk said. As soon as people enter the picture, its really a giant step up in making sure things go right. For sure, the oversight from NASA is much tougher. I thought it was tough for cargo, but its really intense for crew.

It can be a bit tough on the men and women at SpaceX, but I know where its coming from, he said. Its the right motivation, and there will be some debates going into next year about some of the technical details is this right or that right? But I think we really want to make everything humanly possible to make sure it goes well and triple check everything.

Crews riding Dragon spacecraft will blast off on SpaceXs Falcon 9 rocket from pad 39A at the Kennedy Space Center in Florida. SpaceX is working on final modifications to the Falcon 9, which it calls the Block 5 configuration, to meet NASA human-rating safety standards.

Musk said there were some small technical bones of contention, but were working through those.

He did not offer details on the disagreements.

Some (of the) the things are really esoteric, really in the weeds of rocket and spacecraft design, he said. But I think its good to have these debates.

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Propulsive landings nixed from SpaceX's Dragon spaceship - Spaceflight Now