Could Scotland really have a spaceport?
Two Scottish sites are fighting hard to be the UK's first designated spaceport but is the idea pie in the sky or will there actually be lift-off?
Prestwick Airport in South Ayrshire and Machrihanish, near Campbeltown on the Kintyre peninsula, have recently stepped up their attempts to move into the space age.
They have been liaising with the UK government and the UK Space Agency over the possibility of licences being issued to break out of commercial airspace into orbit.
They are now waiting for the government to bring forward a bill setting out the requirements.
How did the idea come about?
It all began five years ago when the UK government announced that Britain should lead the way on commercial space flight and set a 2018 target for getting a spaceport up and running.
The sites needed to be a safe distance from densely populated areas and have a runway that could be extended to more than 3,000m (9,842ft).
The need for a long runway was because the government envisaged the spaceport launching horizontal take-off "spaceplanes", not old-technology vertical rockets.
Most of potential spaceplanes, such as the British-built Skylon, are still quite some time away from flying but ministers wanted the UK to be in position to catch the first wave when it arrived.
There was much talk of spaceports taking tourists on sub-orbital flights but the Scottish space community seems agreed that initially their main business would be delivering satellites into orbit or carrying out scientific research.
Space race competition but no funding
Two years ago a shortlist of five potential sites was announced. In addition to Machrihanish and Prestwick, Stornoway in the Western Isles was mentioned because it was one of the few sites that would be able to accommodate vertical launch rockets.
The Scottish sites were in competition with Llanbedr Airport in Wales and Newquay Cornwall Airport.
However, in May last year the government changed its focus and decided that any airport that met the criteria could become a spaceport.
At the same time it announced a Modern Transport Bill, which would include "legislation to enable the future development of the UK's first commercial spaceports".
Dr Malcolm Macdonald, director of the Scottish Centre of Excellence in Satellite Applications at Strathclyde University, said: "Initially it was announced as a competition between different sites and the government would back a winner.
"They have moved away from that to a licensing process."
What will the spaceports do?
The major interest of ministers and the space industry in a UK spaceport is as a facility to enable satellite launches rather than passenger space tourism.
Small satellite operators have difficulty getting low-cost access to space.
The first satellite designed and built in Scotland was launched in July 2014 via a rocket in Kazakhstan, piggy-backing along with other larger payloads.
Dr Macdonald said: "My feeling is they should have been targeting the launch of small and even nano satellites.
"That is what the sites in Scotland are now looking towards, while at the same time recognising the opportunities that would come along with space tourism."
Dr Macdonald added: "There are companies like OneWeb looking to launch a constellation of 650 spacecraft in the next three or four years to effectively deliver broadband from space.
"They have get them into orbit and they want to do that as cheaply as possible."
"If they can get operational very quickly they may be able to capitalise on that kind of market. There are number of companies looking at these mega constellations."
What is the hold-up?
The UK government's Department for Transport (DfT) told BBC Scotland it had been working hard to develop the Modern Transport Bill but there was currently "no timetable" for its implementation.
A DfT spokeswoman admitted that events over the last year, such as Brexit, had made it difficult to find parliamentary time for the bill.
Dr Macdonald said the Modern Transport Bill was very important as it would bring "clarity" to the regulatory requirements for a UK spaceport.
He said one of the problems would be how the spaceflight would "transition" through the area where civil aircraft are operating would need to be quite well regulated.
"On top of that if you are launching a rocket as an external store on an aircraft or if you are using a spaceplane then the fuel can be quite explosive so you need to have the correct blast radius" Dr Macdonald said.
"There would be a whole range of things that would be required."
Prestwick has done a lot of work in preparation, basing the requirements on those in place in the USA.
They claim it would only cost between £1m and £3.5m to have the airport fit to receive a US licence.
Prestwick Airport's spaceport development officer Richard Jenner said the airport would need to make some modifications but it was confident it already had most safety measures in place.
What are the Scottish sites planning?
The Machrihanish plan is being put together by DiscoverSpace UK.
Its managing director, Tom Millar, told BBC Scotland that vertical take-off was "not on the cards" so it was looking into the options for horizontal launches.
Machrihanish has a very long runway and is not close to large settlements, which meets the original government criteria.
Mr Millar also said that the airspace above the runway had very few commercial flights, taking away the concern over interference with passenger aircraft.
The project is also looking at connecting to a restricted airspace corridor that runs from the Ministry of Defence rocket range at Benbecula.
According to Mr Millar, getting small satellites into space would be a viable revenue stream.
He said the logistics of space tourism "do not stack up at this point".
Prestwick Airport's Richard Jenner said a company called Orbital Access was looking at an air-launch system.
It would use a wide-body carrier aircraft, with special modifications, to support the launch rocket before its release at altitude.
Dr Macdonald says: "They would use an aircraft to get up to altitude. It would carry a launcher rocket underneath the aircraft wings which is released at altitude and it goes up into space from there."
"It is an hybrid solution but would allow you to have a high frequency of launches. It could take off from any airport in terms of the aircraft but because of the rocket there would be a need for additional safety precautions."
Will it happen?
Dr Macdonald says: "I'd be surprised if at least Prestwick does not get a licence.
"Again it comes back to the qualifier that we don't know what the government are looking for but Prestwick have done a lot of work.
"They could start to build up the possibility.
"Whether they will ever become a day to day spaceport, that's quite a long way down the line but in some respects even if you develop the local capability in Scotland to design and build the vehicles that are accessing space but they they go off to operate in China, if they are designed and built in Scotland we are getting a lot of that value anyway."