Aspiring space tourism company Virgin Galactic (SPCE -12.17%) recently announced another setback in its attempts at taking private citizens to space. 

After pushing commercial flights from fourth-quarter 2022 to the first quarter of next year, the latest delay was another three-month move, with a new target date of second-quarter 2023. A three-month delay doesn't seem like a big deal, but here is why investors could start getting impatient.

What's the hold-up?

Management detailed in the company's Q2 earnings call that work on the company's Mothership, which carries the spacecraft to its release altitude before dropping it to come back to earth, has taken longer than anticipated. 

Understandably, setbacks happen, but the company's consistently missed its guided timeline, going as far back as its test flight process last year. 

Virgin Galactic generates virtually no revenue without commercial flights, just $3.4 million over the past year. Meanwhile, the company burned nearly $280 million in cash over that time.

The company took out a $425 million convertible loan earlier this year, which has buffered the business for the near future. It had $1.1 billion in cash and equivalents as of the second quarter.

Cash burn is about to pick up

Virgin Galactic might have trouble affording too many more delays in getting revenue-generating flights in the air. The company's Q2 2022 cash burn was $91 million, and management believes that will increase next quarter to $120 million.

Some upcoming investments will probably cause cash burn to worsen over future quarters. Virgin Galactic is building two new motherships in a partnership with Aurora Flight Services, which will bring next-generation carrier aircraft into service in 2025.

The company is also building a facility in Phoenix that it hopes to have completed by the end of this year. These investments are necessary to expand Virgin Galactic, but they also bring more spending: More people to pay for, more buildings and more air and spacecraft to build and maintain.

Virgin Galactic might need to issue new shares to raise money down the road. The existing $1.1 billion could go faster than expected if the company doesn't get revenue streams started to help offset these costs.

What is Virgin Galactic worth?

Investors can't value Virgin Galactic like a typical stock. There is no revenue or profits to base a valuation on. The company currently has a $1.75 billion market cap, which is essentially what Wall Street is paying for the story of space tourism.

The story is undoubtedly exciting; space has gone from a Hollywood dream to reality. However, investors could change how much they're willing to pay for Virgin Galactic's story if it becomes evident that delivering on that reality keeps drifting into the future.

Virgin Galactic has continued to progress on its plans, even if they take longer than expected. But investors should probably approach the stock as a very speculative investment until there is more meat on the bone to judge the company. Unfortunately, that point might still be a ways off.