All Eyes Are on SpaceX's Next Share Unlock on Sept. 9. But These 3 Unstoppable Growth Stocks Are Better Buys Hiding in Plain Sight.

Space Exploration Technologies (NASDAQ: SPCX) has given investors plenty to get excited about this year. The company's IPO was all the rage this summer, as tech pundits and analysts weighed its impact on the market. But for retail investors, SpaceX has a problem that has little to do with rockets: Its various stakeholders can't sell most of the shares they own -- yet.

When companies go public, their pre-IPO stakeholders -- employees, executives, and other early investors -- can't start selling their shares immediately. Lockup periods are put in place to prevent too many shares from flooding the market in too short a time frame. SpaceX laid out a staggered schedule for the release of those shares over the next year, and the next release date falls on Sept. 9.

Image source: Getty Images.

As of that day, those early shareholders will be able to sell another 319 million shares. That does not mean every shareholder will sell their newly eligible shares. But it does create a potential technical headwind for a stock that entered the public market with a small effective float. SpaceX's own filing also registered shares held by current and former employees for potential resale, meaning investors have to think about supply as well as demand.

That is one reason I'd rather look for opportunities elsewhere in the space and technology markets today. Three companies stand out because their growth stories are tied to infrastructure that still has to be built.

1. Rocket Lab is building the other end of the launch market

Rocket Lab (NASDAQ: RKLB) is not trying to replicate SpaceX one-for-one. Its smaller-payload Electron rocket has given the company launch experience, while its larger Neutron vehicle addresses the medium-lift market. Rocket Lab has said Neutron is intended to support constellation deployments, and it already has dedicated launches booked.

The technical opportunity for the company is bigger than selling launches. Rocket Lab is building itself into an end-to-end space company, with launch vehicles, spacecraft, and components under one roof. That vertical integration can matter because satellite operators don't just need a ride to orbit. They need spacecraft, propulsion, power systems, and the ability to replace aging satellites or expand satellite constellations over time.

Neutron is also the major swing factor. Developing a reusable medium-lift rocket is expensive and carries execution risk, but success could earn Rocket Lab an additional layer of recurring launch demand from commercial and government clients.

2. AST SpaceMobile is attacking a different bottleneck

AST SpaceMobile (NASDAQ: ASTS) is taking another approach to the space economy. Instead of selling launches, it is trying to integrate satellites into terrestrial cellular networks.

Its next-generation BlueBird satellites have phased arrays measuring almost 2,400 square feet and are designed to connect directly with ordinary smartphones. The company's architecture uses its proprietary AST5000 chip, which provides up to 10 gigahertz of processing bandwidth per satellite.

What caught my attention is the pace of the company's build-out. AST SpaceMobile launched BlueBirds 8 through 10 in June and BlueBirds 11 through 13 in August. The company says its production system is designed to build six satellites per month and expects to have about 45 in orbit by early next year.

This is still a capital-intensive bet with real technical and regulatory risks. But each successful satellite deployment moves the company closer to a being continuously available network in its chosen markets rather than another technology demonstration.

3. Redwire is selling the infrastructure behind the infrastructure

Redwire (NYSE: RDW) may be the least obvious name here, but that is what makes it interesting.

The company is developing systems that provide power, manufacturing, and other infrastructure for spacecraft. Its new ELSA solar array is designed for mass-produced satellites and can deliver up to 50% more power per unit volume than traditional arrays. Redwire has also won contracts tied to national security satellites and commercial space infrastructure.

SpaceX gets attention because everyone can understand a rocket launch. The less glamorous opportunity may be the companies supplying key components and hardware for satellite constellations.

None of these three companies is as proven as SpaceX. That is the trade-off. Rocket Lab still has to complete its first Neutron launch, AST SpaceMobile has to grow its satellite constellation into a viable communications network, and Redwire has to execute across a growing set of space and defense programs.

Micah Zimmerman has no position in any of the stocks mentioned. The Motley Fool has positions in and recommends AST SpaceMobile and Rocket Lab. The Motley Fool has a disclosure policy.