Mariners, fishers and seagoing vessels have been warned to stay out of an area of ocean south of Cork and Kerry for a time tonight, due to the fear of potential rocket debris falling from the sky.
The precautionary warning issued by the Department of Transport relates to a mid-air launch of a satellite carrying rocket.
Aviation authorities have also issued warning information for airlines that use the area.
The rocket is being launched by Virgin Orbit, a commercial company set up by Richard Branson to carry satellites into space.
It took off at 10pm and is being flown under the wing of a 747-jet nicknamed Cosmic Girl from Cornwall in England, which will carry the 21-metre rocket to an altitude of 10,668m.
When it reaches that altitude, the rocket will be released, its engines will fire and it will ascend into space with its payload of nine satellites.
All nine are toaster-sized boxes and have a mixture of security and commercial applications. A number of them are from state customers including the US, the UK and Wales - which is putting up its first ever satellite - and Oman.
Capabilities of these satellites, according to the BBC, includes tech to monitor communication transmissions from ships at sea, to counter trafficking, drug smuggling and other illegal activity and there will be experiments on manufacturing in zero gravity situations and weather applications.
The area in question is a huge bottle-shaped area of the Celtic Sea stretching from around 60km off the coast of Cork and Kerry, to around 300km in a southerly direction.
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The rocket will be released from the 747 jumbo jet at around midnight and fly in a southerly trajectory as it ascends into space.
Virgin Orbit said it is the first orbital space launch to originate from the UK and the first time such a rocket launch will be visible live in western Europe.
Irish viewers keen to witness the spectacle may get a glimpse from Cork or Kerry if they look to the southern horizon just after launch.
The company said the rocket should be visible for around 60 seconds from Ireland and after that it will be viewable west of France and on down west of Spain.
The marine notice issued by the Department of Transport said that if the launch goes as planned there will be no debris, but if a mishap occurred there is potential for rocket debris falling, so the request to all mariners is to avoid the area from 10pm until 1am.
Aviation authorities have also warned airlines of the satellite launch activity taking place in the area, and advised them to take the necessary precautions because of the "temporary danger area."
Virgin Orbit is a commercial company that flies satellites into space for commercial and state customers. It has successfully launched 33 satellites over five recent missions.
In a statement, the Irish Aviation Authority said that Irish air traffic controllers will guide the launch aircraft once it enters Irish-controlled airspace.
The authority said it will be coordinated alongside Spanish and Portuguese authorities.
Vice President of Special Projects at Virgin Orbit Will Pomerantz told RTÉ News that this launch is one of the most regulated in history.
"We've had to work very closely with the governments of Ireland, Spain, Portugal and Eurocontrol, and all that is done to make sure there isn't risk to the general public," Mr Pomerantz said.
"I certainly would hope that professional fishermen would follow the notices to mariners and it should be kept in mind that this is not a launch that goes on for days and days, rockets are moving pretty quickly so it's only going to be flying overhead at any given point in time for a fraction of a second," he added.
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Call for more protection for fishermen
The CEO of the Irish South and West Fish Producers Organisation has said there needs to be more protection for fishermen and the environment in these areas.
Speaking to RTÉ's News at One, Patrick Murphy said that "if a mishap were to happen, that means that it explodes and everything that's up there comes flying down from the orbit and down on the top of the heads of people that are in that area.
"This is really dangerous. This is not something that you would just discard," he said.
Mr Murphy also said it is going to impact fishermen's "ability to make a living out there", adding that there has been no consultation or communication on the matter.
"There's areas of the sea where they could do this as well, out into international waters... don't put people's lives in jeopardy when you have an alternative and we believe there's an alternative," he said.
