Jeff Bezos is heading to space. The longtime Amazon CEO announced earlier this month that he intends to board a rocket soon after his planned July 5 retirement from an active role at the e-commerce giant.

Bezos and his brother will be among the first passengers his Blue Origin space company takes into space, the beginning of what Blue Origin hopes is a lucrative space tourism business.

It is an exciting time to be following Blue Origin, and investors surely would love to go along for the ride. But Bezos thanks to his Amazon billions doesn't need outside funding to get Blue Origin airborne, and seems to have no desire to take the company public.

Even if buying Blue Origin shares is out of the question, there are other ways for investors to buy into the growth potential of space. Here's why three Fool contributors believe Maxar Technologies (MAXR), Northrop Grumman (NOC -0.27%), and, believe it or not, General Motors (GM -1.42%) deserve consideration for those interested in out-of-this-world investing.

Graphic of rockets firing into space.

Image source: Getty Images.

In three years, this expensive stock could be a bargain

Rich Smith (Maxar Technologies): I have to admit that I haven't always been a fan of Earth imaging satellite operator and space tech-industrialist Maxar Technologies -- but this stock is starting to grow on me.

After reporting its first-quarter 2021 earnings last month, Maxar was punished by investors for its big loss. At the same time, though, Maxar made significant strides toward fixing its balance sheet in Q1, paying off $350 million in debt and reducing its net debt load to about $2.3 billion. Granted, that's still nearly as big as the company's own market capitalization of $2.9 billion. But it's movement in the right direction, and for that the company deserves some applause.

Also noteworthy is the fact that Maxar is back in positive free-cash-flow territory. With $20 million in cash profit generated over the last four quarters, the company looks on course to finish in the green on free cash flow this year (after burning cash last year). And analysts who follow the stock see FCF rising nearly 600% next year to $188 million as the company wraps up the spending needed to build its new fleet of imaging satellites, then nearly doubling again in 2023 to $349 million, according to data from S&P Global Market Intelligence.

What does this mean for investors? Based on its current enterprise value of $5.2 billion, Maxar stock sells for less than 15 times its likely cash profit just two years out -- and barely 12 times fiscal 2023 projected earnings. That's an appealing price to pay to own one of the leading companies in satellite photography of Earth -- and a key participant in NASA's Project Artemis plan to return to the moon.

A more "defensive" space pick

Lou Whiteman (Northrop Grumman): No doubt, space is cool. And the pace of innovation in the sector is accelerating, which is good reason for investors to get excited.

The problem is, for all the developments space is still a relatively small market. NASA's annual budget sounds impressive at $20 billion-plus, but the part that goes to contractors is hardly bigger than the price of one of the Pentagon's aircraft carriers. Private demand for space services, from tourism to satellites, is steady but niche. There is only so much a pure-play space company can be expected to grow unless something dramatically changes in the market.

Northrop Grumman offers a best-in-class space portfolio inside a massive defense arsenal. The company has a long history as a government space leader that was boosted by its 2018 acquisition of Orbital ATK. Today Northrop's space business is involved in launch and propulsion systems, human spaceflight, commercial satellites and payloads, and a large top-secret component.

Rendering of the RapidStar-2 satellite in orbit.

Northrop Grumman's NOC RapidStar-2 national security satellite. Image source: Northrop Grumman.

Space has been a standout performer inside Northrop. The space business grew sales by 29% in the most recent quarter, doubling its backlog in 2020. Overall space generated $2.5 billion in revenue in the quarter, accounting for about 27% of Northrop's total sales.

In Northrop investors get not just an impressive space franchise, but also Pentagon priorities including an $85 billion program to replace the nation's intercontinental ballistic missile and a separate $50 billion franchise to develop the new B-21 bomber. Northrop's aerospace and space chops should also help the company win a growing share of contracts related to the development of hypersonics, missiles capable of traveling more than five times the speed of sound.

Northrop Grumman provides investors a way to buy into an industry-leading space portfolio and have the benefits of a company with a $80 billion backlog of orders and a 1.7% dividend yield. All of that at a reasonable 13 times earnings and 1.6 times sales. 

Given the risks and uncertainty of pure-play space investments, it is one of the more attractive ways to buy into the modern-day space race.

How this old automaker could become a critical space supplier

John Rosevear (General Motors): GM is many things, but is it really a space company?

The truth is, although GM has played some interesting roles in America's space-exploration efforts over the years, GM isn't really a space company -- at least, not yet.

But the auto industry's pivot to electric and connected vehicles has led GM to develop some interesting new lines of business, and there's at least one that could play a meaningful role in efforts to explore and commercialize space in the years to come: Fuel cells.

Fuel cells are devices that chemically convert the energy in hydrogen gas to electricity, emitting only water. They've been around for decades -- and GM has been tinkering with them for over 50 years -- but it's only recently that efforts by GM and others to make them commercially viable have started to bear fruit. 

A cutaway drawing of GM's Electrovan, showing the fuel cell system that took up much of its interior.

The world's first electric vehicle powered by a hydrogen fuel cell was GM's Electrovan, developed in 1966. Image source: General Motors.

GM's "Hydrotec" fuel-cell systems use fuel cells manufactured by a joint venture between GM and Honda Motor. (Honda uses the fuel cells in its own separate line of products.) Just in the last several months, GM has struck deals to develop Hydrotec fuel-cell systems to power heavy trucks with Nikola and Navistar International, for railroad locomotives with Wabtec, and for aviation with German aerospace supplier Liebherr-Aerospace. 

Could space be next? I think it's likely. After all, GM also recently announced a deal to partner with Lockheed Martin on a new lunar rover -- 50 years after GM helped to develop the first lunar rover. 

More broadly, GM's unfolding plan to become a major fuel-cell supplier will provide an intriguing new stream of revenue that isn't dependent on the ups and downs of global auto sales. As GM moves beyond cars and trucks to become a provider of mobility-related services and products (like fuel cells), its bottom line and its stock price both seem likely to benefit.