Space Adventures’ offer of real-live spacewalks to paying customers appears to be a logical next step in the evolution of space tourism, but a number of important details and issues must be addressed before this can happen.

Chief among them is prior approval from NASA and its partners on the international space station, outside of which the proposed sightseeing spacewalks would take place. NASA might be reluctant, just as it was when Space Adventures brokered the first flight of a paying private citizen to the space station aboard a Russian Soyuz capsule.

Dennis Tito’s historic space station visit back in 2001 was presented to NASA by Space Adventures’ patron, the Russian Federal Space Agency (Roskosmos), as something of a fait accompli. The U.S. space agency ultimately acquiesced, and a new industry was born, with no apparent disruption to official space station activities.

Spacewalks, of course, are a bit more complicated and more risky. The onus is on Space Adventures and Roskosmos to show that these 90-minute jaunts outside the space station will not disrupt other activities aboard the facility. Space Adventures and Roskosmos also should account for and cover the cost of space station resources directly consumed as a result of these activities, including astronaut time.

For example, spacewalking tourists will have to be escorted by a Russian cosmonaut who might otherwise be doing maintenance or conducting experiments. Russia is being paid for that, but other station crew members likely would have to monitor the activity, and stand ready to execute life-saving contingency plans in case something goes wrong.

There also is the question of whether spacewalks by amateur astronauts are at all compatible with space station assembly, which is set to resume in August and continue for the next several years.

In a press release issued July 21, Space Adventures said that for $15 million, which would be in addition to the standard $20 million fee for space station visits, “clients can now participate in a spacewalk” during their stay.

The announcement might have been a bit premature. NASA said the same day that it had yet to be informed of the Space Adventures-Roskosmos spacewalk plan and reiterated that there is a process by which extravehicular activity aboard the space station is approved.

Even Roskosmos, which has no qualms about hauling tourists to the space station in exchange for cash, sounded a note of caution. In a vaguely worded press release posted on its Web site July 24, the agency acknowledged the possibility of tourist spacewalks at the space station and said one prospective customer has displayed an interest in such an experience. But Roskosmos also indicated that this person has not yet been approved for a spacewalk by Russian specialists. The press release also said a Roskosmos official was quoted in the media as saying that the price for spacewalk experiences has yet to be determined.

Of course, there is always the possibility that Roskosmos will quickly come to closure on any outstanding issues on its end once it has a firm cash offer in hand. Space Adventures, meanwhile, can hardly sell a product whose availability is uncertain, so it is only natural that the company would downplay any potential snags.

The opening up of space to private citizens, though limited for now to a very-wealthy few, is among the most important recent developments in the annals of spaceflight. To date, it has had a positive impact, stirring up new interest around the world and fueling hundreds of millions of dollars of investment. Billionaire Robert Bigelow’s recent successful test of a prototype space habitation module — he envisions a chain of motels in Earth orbit — is a prime example. Airline and music tycoon Richard Branson’s plan to build a fleet of suborbital space tourism vehicles is another.

Just a few years ago, such ideas were easily dismissed as fanciful. Not anymore, thanks in large part to pioneering and entrepreneurial spirit of Mr. Tito, Space Adventures and, yes, Roskosmos.

The world’s space agencies can and should play a role in keeping this ball rolling, which is why NASA and the other space station partners must keep an open mind — Roskosmos likely will need little convincing — toward the very intriguing possibility that Space Adventures has put forward.

But Roskosmos and Space Adventures must not present any tourist spacewalk plan as another fait accompli. Taxpayers did not invest tens of billions of dollars in this project to create an orbital amusement park for wealthy adventure seekers. There is a protocol to be followed here, and if Roskosmos and Space Adventures cannot show a clear plan that accounts for the cost of tourist spacewalks — and keeps the resulting disruption to space station science and maintenance to a bare minimum — then the idea should be rejected.