Chris Hadfield says Nasa's job is not to 'titillate'
Space station commander Chris Hadfield has told BBC News that those calling for a quick return of manned missions to the Moon are seeking "titillation".
His comments were in response to suggestions that the International Space Station (ISS) served little purpose.
Commander Hadfield has been a Twitter sensation with his feed of comments, photos and videos showing what life is like in space.
He is due to return to Earth on Tuesday.
"We will go to the Moon and we will go to Mars; we will go and see what asteroids and comets are made of," he told BBC News.
"But we're not going to do it tomorrow and we're not going to do it because it titillates the nerve endings. We're going to do it because it's a natural human progression."
I met Chris Hadfield in his native Canada last year before he went into space. At the time, morale was running low within Nasa following the scrapping of the shuttle programme, the cancellation of the previous administration's plans to go back to the Moon and Mars and mounting criticism of the quality and quantity of research on the ISS.
But every inch the archetypal, twinkly-eyed, optimistic astronaut, he was having none of it.
"It's a process - we're not trying to make a front page every day and we're not planning on planting a flag every time we launch. That's just a false expectation of low-attention-span consumerism".
Those growing up in the 1960s were inspired by views of the Earth from space and the Moon landing. A new generation has become enthralled by commander Hadfield's frequent tweets on what it is like to live in space.
He has shown his nearly 750,000 followers how astronauts brush their teeth and how to eat a tortilla in zero gravity. Commander Hadfield has also sung along with schoolchildren from space and chatted with William Shatner, who played Captain Kirk in the original series of Star Trek.
He has probably become the most famous astronaut since the days of Neil Armstrong and Yuri Gagarin.
And so many now want to know more about their new superstar. What, for example, does he think of the future of space travel? When I spoke to him in February 2012, I asked him whether he thought that astronauts would ever again leave low Earth orbit and go back to the Moon, or perhaps one day on to Mars, rather than simply ferrying back and forth to the space station.
It was an honest enough question, but I realised as soon as he began to answer that it was a tactless one, because it implied what he and his fellow astronauts were doing was pointless.
"That's a really self-defeating way of posing the question because you say 'get back to' and 'ferrying back and forth'," he said, clearly irked.
I felt bad that I had irritated such a nice man, but my question had spurred him to deliver a passionate and articulate case for the ISS.
"We are leaving Earth permanently," he said with zeal. "It is a huge historic step and we are trying to do it right and it takes time, it takes patience and it takes tenacity - and we're going to do it."
His argument is that the construction and utilisation of the ISS will lead to the development of technologies that will eventually enable humanity to leave Earth and settle on other worlds. But that process will be a slow and incremental one.
And he has this to say to those who want things to move much faster: "It's just an uninformed lack of patience and lack of understanding of complexity and a desire to be amused and entertained that builds a false set of expectations."
One of the key technologies that is needed is a means to recycle water from astronauts back into a drinkable form, along with radiation shielding and developing ways of working and living in space for prolonged periods.
Commander Hadfield believes that the ISS provides the perfect test bed for developing deep space travel capabilities.
"We are slowly leaving our planet and it happens in little, [difficult-to-execute] and hard-earned steps and it makes huge sense to understand how to do it when we are only 400km (250 miles) away.
"Because we can at any moment, when we have made a stupid mistake with a design, or an emergency that we hadn't recognised or because of human health, get in our spaceship and come home."
That is a view backed by Dr Simon Evetts of the UK Space Biomedical Association.
"The operational experience is significantly important because we are learning how to live in space and so I think that the ISS probably will be a stepping stone to Mars."
But what about the science? One of the space station's key selling points was that it would be an orbiting laboratory where scientists from across the world would work in space to roll back the frontiers of knowledge.
Critics such as the UK's Astronomer Royal, Prof Lord Rees, have questioned whether the hefty £65bn ($100bn) it cost to build the ISS would be value for money.
"No one would regard the science on the space station as being able to justify more than a fraction of its overall cost," he said.
"I recall in the early days there were some proposals for experiments and the [UK] research councils would not even pay for the modest, marginal cost for them so we have to ask whether people would be prepared to pay for [the experiments on the ISS] had they to be financed in competition with other work on the ground".
Lord Rees cites a $1.5bn cosmic ray experiment bolted on to the ISS as an example of money which could be better spent.
"The results from the Alpha Magnetic Spectrometer (AMS) are still rather ambiguous and the general opinion is that the experiment has not justified its cost and would not have been flown had there not been lobbying which put it ahead of competing projects."
One of the main areas of research on the ISS is to see how materials and biological systems behave in the microgravity of space. But project proposals have been slow to emerge.
A report by the US National Research Council in 2011 highlighted that Nasa's efforts to maintain its human spaceflight programme had led to a decline in life and physical science research - "leaving it in a poor position to take advantage of the fully equipped ISS".
Faced with the embarrassing prospect of an underused multi-billion dollar space station, Congress created an independent, non-profit organisation, the Centre for the Advancement of Science in Space (Casis), later that year.
It was tasked with bringing in research projects from the US research community while Nasa concentrated its research efforts on developing technologies for long term space travel of the sort that Cmdr Hadfield describes.
But projects were slow to emerge and within a few months the organisation's director resigned abruptly citing "unrealistic expectations" by Nasa and congressional officials.
A large part of the problem is that there is currently no evidence that studies on topics such as bone thinning, growing stem cells or proteins in microgravity will lead to any useful new treatments. Without this, many in the research community can't see the virtue in such research.
But Casis's upbeat new chief executive, Duane Ratliff, told BBC News that he believed that once there was evidence that these research areas might be fruitful, scientists would be falling over themselves to book a research slot on the ISS.
"You then have a compelling research pathway, [so] if we can demonstrate the significance of the ISS as an R&D platform, there will be specific industries that will want to take advantage of that."
In Europe, by contrast, there is no shortage of research ideas, many of which will be discussed at a space environments conference at the UK's National Space Centre in Leicester in November. Dr Evetts says that researchers putting proposals to the European Space Agency are aware that microgravity research is a long haul.
"We can't really assess the importance of what we are getting out of the ISS now. We'll probably understand that in the decades ahead so we should not be too quick to judge," he said.
Lord Rees, however, believes that the ISS is not a cost-effective way to do science.
"Its main [purpose] was to keep the manned space programme alive and to learn how humans can live and work in space. And here again the most positive development in this area has been the advent of private companies which can develop technology and rockets more cheaply than Nasa and its traditional contractors have done".
So the ISS's value for science and even as a staging post for deep space travel is not clear-cut.
But as Chris Hadfield has shown, its ability to inspire is undisputed and perhaps deserves the patience that he has called for to inspire a generation to learn about science and space travel.
Follow Pallab on Twitter @bbcpallab