Will offshore launches solve the spaceport bottleneck?

"I don't want to go back to a world where we don't have satellite communication because it would be a poorer, hungrier and dirtier, polluted world," said Tom Marotta at The Spaceport Company.

But we have a problem, Marotta said, and it's called the "spaceport bottleneck". Land-based spaceports in the US are congested, so we can't launch satellites — especially small satellites that service today's growing demand for mobile communication — as quickly as people seem to want or need them. 

If spaceports are so congested, you may wonder, shouldn't we address our growing demand first and launch fewer of them? When roads get congested and the air polluted, don't we encourage people to drive less and ride a bike instead, or walk. Yes, but not in space. We keep firing satellites up. And it's not just the launchpads that are congested, but space itself.

Space saturation: When will there be be too many satellites? 

Low-Earth orbit (LEO), at a range of about 160-2,000 kilometers (99-1,242 miles) above ground, is where most of our satellites go. That includes Earth Observation satellites that monitor the state of our environment. It's also home to the International Space Station (ISS).

It's estimated there will be between 58,000 or close to 100,000 new satellites in space by 2030. That's up from current numbers of 5,500 - 6,700 in LEO.

"Now is the time to build more launchpads because the demand for data from space is greater than it has ever been before," said Marotta. "But in the US, only four spaceports are regularly sending satellites to orbit. And as you know, Europe has none."

Europe does, in fact, have one spaceport at Kourou in French Guiana, but none on the European continent. The UK is fairly advanced with its plans for onshore spaceports at Sutherland, Snowdonia and Cornwall, the latter of which is licensed and operational. And there are others, such as at Andoya in Norway.

What's a mobile offshore spaceport?

The basic idea behind a mobile offshore spaceport is all in the name. It's a launchpad located relatively close to a coastline but at sea, where it is no danger to humans, other animals or the land-environment. And it's mobile, operated either from an open-ended barge, similar to cargo vessels, or a liftboat (also known as a jack-up platform) that looks like an oil rig.

Because they are mobile, offshore spaceports can (theoretically) move if weather conditions turn sour, and allow a launch to go ahead. Land-based launchpads can't do that — they tend to sit on top of deep craters and are dependent on good weather conditions.

Offshore spaceport experts like Marotta or Alain Pajonk, project manager for the German Offshore Spaceport Alliance (GOSA), have said sea launches don't need exhaust trenches, and that makes them more mobile.

What impact do offshore spaceports have on the ocean?

Offshore spaceports do make one wonder whether rockets launched at sea will boil the ocean or marine life — rocket engines generate thousands of kelvin in heat (1,000 kelvin = 726.85 degrees Celsius, or around 1,340 Fahrenheit).

Pajonk said the consideration is irrelevant. "We're talking about a few seconds, after which your launch vehicle is already 700 meters away. There is almost no interaction with the ocean water. There will be some exhaust and chemicals from the combustion, but the quantity is not environmentally relevant," he said.

Will it be possible to launch different rockets from the same pad?

An offshore spaceport should also cater to more than one type rocket, said Pajonk. Land-based launchpads tend to be built for one specific, often heavy launch vehicle, like a SpaceX's Falcon 9, Blue Origin's New Glenn or Europe's Ariane 5 and 6.

"You need new pads for the new launch vehicles and we're not seeing pads that are built for multiple [types of] launch vehicles," said Pajonk, whose German Offshore Spaceport Alliance is planning a spaceport in the North Sea.

Both Pajonk and Marotta said most commercial demand these days is for small satellite launches on smaller rockets, such as Europe's Vega, Rocket Lab's Electron or Firefly's Alpha. But servicing different types of rockets all in one place may be harder than it sounds.

"The idea that any launchpad, at sea or on land, can accommodate multiple different launch vehicles is theoretically fine, but in reality doesn't work out," said Malcolm Macdonald, a professor in satellite engineering at the University of Strathclyde, Glasgow.

"That was the plan for both Shetland and Sutherland [spaceports in the UK], yet both have ended up developing pads for each different vehicle as they each have slightly different requirements, so I'd expect a future sea launched system to end up in a similar position," he said.

Ultimately, the industry would like to see common standards as in the commercial airline and airport industry, but that appears to be a way off for the space industry.

What types of offshore spaceports are there?

The Spaceport Company aims to start with jack-up platforms located about 5-20 kilometers from the coast — "close enough so that if a technician has to run out to the platform to repair the rocket, or refuel the generators on the platform," said Marotta.

But "operating at sea is a punishing environment," Marotta said. Salt corrosion and severe weather are just two of the considerations, but there's plenty to learn from the gas and oil, and offshore wind industries.

Jack-up platforms get their name from the fact that they have legs that extend down toward the seabed, enabling the platform to rise above the water. They are "perfectly stable," said Marotta. "The downside is that [they] only operate in relatively shallow waters — about 50-60 meters."

That means you couldn't use a liftboat off the Azores in the Atlantic, for instance, which the GOSA team considered before opting for a floating barge.

"Of course, you're more stable with the legs than when you're floating, but not fully stable, you do still have some drift, " said Pajonk.

In the North Sea, GOSA's floating barge would sit about 180 nautical miles (333.36 kilometers, 207.14 miles) offshore — it couldn't be much closer due to other ocean traffic. "But if we wanted to launch from the Azores, we could be a few miles away from the shore," said Pajonk.    

So, a floating barge offers the potential of launching from a few more locations. But a jack-up platform, on the other hand, offers an option for reusable rockets as well. "We're designing our system to be modular," said Marotta, "we can serve more types of [rockets], we can turn it into a landing platform, so it's a lot more flexible than a ship-based platform."

Will offshore spaceports achieve more launches than land-based launchpads?

Both The Seaport Company and GOSA said offshore spaceports will increase the "cadence" of launches — there'll be more satellites launches, more frequently.

While The Seaport Company's Marotta said 12-18 launches per platform were feasible for them, GOSA's Alain Pajonk said they were aiming for 12-24 launched per month per launchpad.

"That is a lot!," said Macdonald. "And so, the scale does appear to be there […], and if they can do final integration on the transfer ship rather than in a hanger at the launch site, then maybe it will be fine."

In both cases, there won't be any people at the launchpad at the time of launch. All missions will be run from control centers onshore.

Sea Launch: a failed pioneer?

Before The Spaceport Company and GOSA, there was the Sea Launch company, an international joint venture that included American, Russian, Norwegian and Ukrainian partners.

They operated in international waters on the equator, using a large command ship for personnel to run the launch operations and a mobile oil platform as a launchpad. The company was reportedly limited to commercial customers, with no government contracts to sustain its business, and was famed for a spectacular explosion during a launch in 2007 that forced the venture into bankruptcy.

Since then, one or two Chinese ocean-based launch initiatives have taken up the mantle. The private space company, Galactic Energy, successfully launched a Ceres-1 rocket from a floating platform near Hainan Island in September, putting four satellites into orbit.

There are also plans for ocean spaceports off the coasts of Ireland and Denmark.

Edited by: Fred Schwaller