Orion on its launchpad in Cape Canaveral, Florida. Photograph: Joe Raedle/Getty Images

Mankind will take its first steps on the path to landing on Mars on Thursday, according to Nasa. The first test flight of the Orion spacecraft, the intended successor to the space shuttle, is scheduled to launch from Cape Canaveral just after dawn.

The unmanned $370m (235m) mission, formally known as Exploration Flight Test-1 (EFT-1), will last about four and a half hours. The success of this test is crucial for the future of Nasas human spaceflight exploration programme, said Dr David Baker, a former Nasa engineer.

Once in orbit, the conical Orion capsule will circle Earth twice, reaching a maximum altitude of 3,600 miles. At about 15 times higher than the International Space Station, it will have travelled further into space than any crew capsule has gone since the 1970s.

Orion will then plunge into Earths atmosphere at 20,000mph. This will generate temperatures of around 2,200C, which is representative of a re-entry from lunar orbit. A newly designed 16ft-wide heat shield will protect the spacecraft from burning up, allowing it to splash down off the coast of Baja California, in the Pacific, from where it will be recovered by Nasa and the US Navy.

Really this is just a test of the Orion heat shield, said Baker, who worked for Nasa for 25 years, including during the Apollo moon landings.

Beneath the hype and the excitement, there are worries that Nasas Mars programme lacks focus. The Nasa PR machine is good at bigging things up, but I think to say that this is the road to Mars is a bit much, said Ian Crawford, an astronomer and advocate of human spaceflight at Birkbeck, Univeristy of London.

Nasa says it is aiming to carry out a Mars mission in the 2030s, but there are no definite plans at the moment beyond the present one a collaboration with Sesame Street. Items including Ernies rubber ducky, Oscars pet worm, Slimey, and the Cookie Monsters cookie are being taken into space by Orion and will later be displayed on the childrens television show in the hope that they could inspire the next generation of astronauts. Nasa predicts that the first astronauts on Mars will be todays pre-schoolers.

The capsule itself is largely devoid of anything required for a human crew, such as life-support and command consoles. Instead it will be packed with 1,200 sensors to test its durability.

Orion is the first new Nasa spacecraft designed to transport humans into space for a generation. Its predecessor was the space shuttle, retired in 2011 after a 30-year programme during which there were 133 successful flights and two fatal disasters. With the shuttles retirement, Nasa lost its ability to launch astronauts into space. For the last three years it has been forced to buy seats on Russian Soyuz launches.

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Nasas space shuttle successor Orion set for first test flight