Nearly half of Americans want to travel to space.

But that means the other half doesn’t, according to a 2021 survey by ValuePenguin, one of LendingTree's financial research websites. Nearly 40% said space travel was too dangerous, while others worried about environmental impact and costs.

Soon there will be an option that addresses those worries, according to companies that plan to send passengers into "space" via high-altitude balloons.

In reality, the balloons rise less than half the distance to the technical definition of space, but that's still nearly three times higher than most commercial flights travel — and high enough to see the Earth's curvature.

Rather than a bone-rattling rocket launch, balloons are "very gentle," said Jane Poynter, co-CEO at Space Perspective, which hopes to take passengers to the stratosphere in 2024.

There are no face-contorting "high Gs," training isn't required and trips don't release carbon emissions either, she said.

The Florida-based company is using hydrogen to power its six-hour journeys, which Poynter said are going to be so smooth that passengers can eat, drink and walk around during the flight.  

Hydrogen is being hailed as the "fuel of the future" — a potential game-changing energy source that could alter the world's reliance on fossil fuels.

But after a series of conversations with people in the field, CNBC Travel found a lack of consensus on its safety.

What's new?

Stratospheric balloons aren’t new — they’ve been used for scientific and weather research since the early 20th century.

But transporting groups of paying passengers in them is. 

Poynter was part of the team that helped former Google executive Alan Eustace break the world freefall record when he jumped from a stratospheric balloon nearly 26 miles above Earth.

While Eustace hung under a balloon wearing a spacesuit, Space Perspective’s passengers will travel via a pressurized capsule, which can fit eight travelers and a pilot, she said. The capsule is backed up by a parachute system that has been flown thousands of times without fail, she said.

“In all of the conversations that we have with people, safety is the first thing that comes up,” Poynter said during a video call from Florida’s Kennedy Space Center. “This is truly the safe way of going to space.”

An 85-year-old 'PR problem'

In December 2017, a hydrogen-filled balloon exploded at the Tucson, Arizona, facilities of a stratospheric balloon company called World View Enterprises.

At the time, Poynter was World View’s CEO. She and her business partner and husband Taber MacCallum co-founded World View in 2012. They exited the company in 2019 and formed Space Perspective the same year.

A report by the Arizona Division of Occupational Safety and Health, obtained by CNBC under the Freedom of Information Act, stated that an on-site manager suspected “static electricity” ignited the hydrogen. According to the report, the accident occurred during a ground test, while the balloon was being deflated, and did not cause serious injuries.

An electrostatic discharge, i.e. a spark of static electricity, that ignited flammable hydrogen gas is widely believed to have caused the Hindenburg airship disaster in 1937.

But Peter Washabaugh, an associate professor of aerospace engineering at the University of Michigan, said hydrogen was inappropriately blamed for the Hindenburg crash.

“The outer covering of the vehicle was flammable. It is not clear what caught fire first — the covering or the hydrogen,” he said. “The craft was being operated aggressively during a storm… I would say it was operational negligence.”

Washabaugh said technological advances have made using hydrogen safer.   

“Lots has changed in the last 100 years,” he said, noting that newer balloon materials “are specifically better at containing hydrogen.”

Robert Knotts, a former engineering officer with the U.K.’s Royal Air Force and current council member of England’s Airship Association, agreed.

He co-authored an article in the Royal Aeronautical Society, a professional body for the aerospace community, which stated: “Modern materials and sensors could make a hydrogen airship as safe as any helium airship.”

Mention hydrogen with either airships or balloons and “everybody's mind goes back to the Hindenburg — that's the picture they have,” he said, calling the incident a “major PR problem” for the gas.

Meanwhile, hydrogen is now used to power electric cars, while airliners (“God knows how many gallons of fuel are on board”) carry inherent fire risks too, he said.

Helium vs. hydrogen debate

World View's current CEO Ryan Hartman told CNBC that its space tourism balloon flights, which are scheduled to launch in 2024, will be powered by helium.  

After noting that “our company is a very different company today,” he said: “Our decision … is purely from a perspective of wanting to do something that is as safe as possible for passengers.”

He called the use of hydrogen to carry passengers to the stratosphere “an unnecessary risk.”

Hartman said hydrogen is used to launch balloons when “the risk is low,” which makes sense, he said, because it’s cheaper and is a very high-quality lift gas.

In 2018, Poynter — World View's CEO at the time — told CNBC that World View doesn’t use hydrogen with its balloon systems.

But her new company, Space Perspective, is now choosing to use it to join the rapidly growing hydrogen economy, she said.

“Helium is in very scarce supply and is needed by hospitals for tests for the very ill as well as to launch communication satellites and conduct important research,” she said. “With helium shortages already occurring, it is unsustainable to use helium for space tourism flights at scale.”

Plus, "hydrogen has been proven to be very safe as a lift gas," she said.

A movement to hydrogen?

Space Perspective’s decision is part of a larger movement to return to hydrogen, said Jared Leidich, a former employee of World View and current chief technology officer at the stratospheric balloon aerial imagery company, Urban Sky.

“Hydrogen can absolutely be a safe gas,” he said, noting that there is “a ton” of precedent for using it in other regions of the world.

As to whether he would ride a balloon into his stratosphere: “Absolutely,” said Leidich. Hydrogen or helium? It wouldn’t matter, he said, noting that hydrogen can make aspects of the ride safer “because it's a more efficient lift gas, the whole system can end up being smaller, which has some cascading benefits.”

He said he's already booked a seat — and paid a $1,000 refundable deposit — for a Space Perspective flight.

Knotts also said that the choice of gas “wouldn't bother me, quite frankly."   

Others weren't so sure.

Kim Strong, an atmospheric physicist and chair of the University of Toronto’s Department of Physics, told CNBC she’d “feel safer with a helium-filled balloon.”

But University of Michigan’s Washabaugh said he's on the fence about riding in a stratospheric balloon.

“It would not matter if it was H2 or He," he said in an email. "I’m just more fond of a powered vehicle.”

A complex transition

Persistent talk of an impending helium shortage has caused “almost all” balloon companies Leidich works with to develop systems that are compatible with hydrogen and helium, he said.

The Brooklyn-based stratospheric balloon imagery company Near Space Labs currently uses helium, but CEO Rema Matevosyan said it’s exploring using hydrogen in the future.   

“The advantages of hydrogen are there. All the issues with hydrogen are there as well, and everybody knows it,” she said. “It’s going to be a very complex transition … it's going to take research … the demand for this will also drive some of the research.”

EOS-X Space, a Madrid-based stratospheric balloon company that is preparing to launch space tourism flights from Europe and Asia, is planning to make the switch.

“The first flight test this next quarter will be powered by helium,” said founder and chairman Kemel Kharbachi. But “our engineers and the development and innovation team are working with hydrogen so that we can be the first before 2024 to have this technology.” 

Others are sticking with helium.

Jose Mariano Lopez-Urdiales, the founder and CEO of the Barcelona-based stratospheric balloon company Zero 2 Infinity, told CNBC his company's space tourism balloon rides will use helium “of course.”

“Our investors and clients want to avoid at all costs these kinds of fireworks,” he said via email, referencing a YouTube video showing the World View ground test balloon explosion.

He didn't rule out using hydrogen in the future though, saying his company could, after "a few thousand successful hydrogen flights, then little by little introduce it in a controllable way to crewed high altitude flights."

Lars Kalnajs, a research scientist at the University of Colorado’s Laboratory for Atmospheric and Space Physics, agreed, saying hydrogen use could be an uphill battle since stratospheric tourism is a new and unproven venture.

“Risk — or even the perception of risk — will be a significant hurdle,” he said, “at least until the safety of the overall system is very well proven.”

Not exactly ‘space’

While Hartman and Poynter may disagree about which lifting gas to use, they both said stratospheric balloon rides are far safer than rocket-based space travel — and much cheaper.

Tickets on World View’s capsule cost $50,000 per seat, while Space Perspective is currently reserving seats for $125,000. Both companies said all U.S.-based flights are sold out in 2024.

Yet unlike Virgin Galactic, Blue Origin and SpaceX, stratospheric balloons don't go close to space, said Kalnajs. Most balloons will travel 30 to 40 kilometers (about 19 to 25 miles) high, which falls short of the internationally recognized boundary for space — the so-called “Karman Line” — set at 100 kilometers above sea level.

Still, it’s high enough to see to see the "iconic thin blue line" of Earth's atmosphere, said Poynter.

John Spencer, the founder and president of the Space Tourism Society, said stratospheric balloons are part of the "space community."

“As far as I am concerned, they are providing a space experience with their balloon flights — and one many more people can experience than those who will be willing to get into a rocket ship,” he said.

Spencer said he is a friend of Poynter and her partner, MacCallum, and is interested in taking a balloon flight with their company.

“But I would rather see them use helium,” he said.