Prominent billionaires Richard Branson and Jeff Bezos made history this month by becoming the first space tourists in human history when they each made brief trips into space.

Now, a Democratic lawmaker is already proposing imposing a tax on such activities.

What are the details?

Rep. Earl Blumenauer (D-Ore.) has announced the the Securing Protections Against Carbon Emissions Tax Act that would enact an excise tax on "commercial space flights carrying human passengers for purposes other than scientific research."

The tax would be per passenger.

More from Blumenauer's press release:

It would also include a two-tiered excise tax for each launch into space. The first tier would apply to suborbital flights exceeding 50 miles above the Earth's surface but not exceeding 80 miles above the Earth's surface. The second tier, which would levy a significantly higher excise tax, would apply for orbital flights exceeding 80 miles above the Earth's surface.

"Space exploration isn't a tax-free holiday for the wealthy. Just as normal Americans pay taxes when they buy airline tickets, billionaires who fly into space to produce nothing of scientific value should do the same, and then some," Blumenauer said in a statement.

"I'm not opposed to this type of space innovation. However, things that are done purely for tourism or entertainment, and that don't have a scientific purpose, should in turn support the public good," he added.

The crux of Blumenauer's concern is the environment. He claims routine space flights will cause undue burned on the climate. What is not clear, however, is how implementing a tax on space travel protects the environment or lessens the potential environmental impact of regular space travel.

Anything else?

Branson and Bezos were the target of progressive critics who complained about the amount of money each man spent on their brief trips into the heavens. Critics claimed the money would be better spent on initiatives toward improving lives on Earth.

But it's clear space tourism is piquing interest.

According to the Washington Post, Blue Origin, the company owned by Bezos, has already sold $100 million worth of tickets to space. Branson, meanwhile, is selling tickets at $250,000 apiece.

Elon Musk, the second-richest man in the world, also has cosmic aspirations. However, he reportedly does not have plans to travel to space himself — at least right now. Musk appears to be set on helping NASA continue its current scientific missions in the form of multibillion-dollar contracts.