What happened

Space tourism pioneer Virgin Galactic (SPCE 3.15%) is blazing new trails, and investors are cheering. Earlier this week, the company tweeted out the crew list for its next space tourism flight, Galactic 02.

And while investors didn't react very much on the day of the news (nor on the day after), on Wednesday it seems they're rethinking that. Traders bid up Virgin Galactic stock by a strong 4% as of 2:46 p.m. ET.

So what

The question is whether investors are making the right call here -- because to be frank, I don't think they are.

On the one hand, Galactic 02 promises to both advance Virgin Galactic one more step toward its goal of flying monthly missions to the edge of space (and generating consistent revenue), and also generate publicity for the company. To the latter end, Virgin Galactic is loading its second commercial spaceflight with a crew that includes a mother and daughter from the Caribbean, and an 80-year-old former Olympic canoeist who now has Parkinson's disease.

Other investors seem to like this.

Now what

But it's Virgin Galactic's first -- and as an investor, I'd argue its primary -- goal that concerns me. Consider: When first built, Virgin Galactic's Unity spaceplane was advertised as capable of carrying six paying passengers to space and back. But the company's first commercial flight, Galactic 01, carried only three paying passengers.

Now, its second commercial spaceflight is carrying only three passengers as well.

That means that both of these first two flights generated/will generate only half the revenue they might have. If it turns out there's some essential reason for flying the spaceplane only half-full (other than simply wanting to minimize risks in the first few flights), then this cuts in half the company's revenue potential, potentially doubles the time it will take Virgin Galactic to turn profitable, and correspondingly reduces its attractiveness as an investment.

When you consider further that two of the three passengers flying with Virgin Galactic next month (the mother-daughter duo of Schahaff and Mayers) may be flying for free (at least one media report notes that the passengers won their tickets in a sweepstakes that raised funds for the nonprofit Space for Humanity), it's an open question as to whether the value of the publicity generated by the flight will offset the revenue lost to Virgin Galactic.  

However the math works on that, I'm doubtful it justifies a 4% increase in Virgin Galactic's stock price.