Growth investors hunting for the next big thing face a classic dilemma: Wait for proven winners at premium valuations, or take calculated risks on emerging technologies before Wall Street catches on.

This week, two speculative plays deserve attention -- not because they're safe, but because their risk-reward profiles have shifted dramatically. AST SpaceMobile (ASTS 3.95%) and Rigetti Computing (RGTI -0.51%) are attacking trillion-dollar problems with revolutionary solutions, and recent developments suggest the market might be underestimating their potential.

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The anti-Starlink play

While SpaceX dominates headlines with Starlink, AST SpaceMobile is building something potentially more disruptive: satellites that connect directly to unmodified smartphones. No special equipment, no new devices -- just your regular phone connecting to space when terrestrial towers can't reach you. Partners include AT&T, Verizon, Alphabet's Google, and Vodafone, covering billions of potential subscribers through carrier relationships.

The numbers are turning real. AST projects $50 million to $75 million in revenue for the second half of 2025 from government and commercial sources. Six satellites orbit now, with 45 to 60 fully funded birds planned by 2026. The stock has responded accordingly, up 135% year to date.

Wall Street maintains a "buy" consensus with a $49 average 12-month target, barely above current levels. But here's what skeptics miss: AST isn't competing with Starlink. Starlink typically requires dedicated hardware and about $120 monthly for residential service. AST makes your existing phone work everywhere, partnering with carriers rather than competing against them. Different market, different economics.

The risks are real: massive capital requirements, launch risks, regulatory hurdles across jurisdictions. Shares, accordingly, have whipsawed between $20 and $50 this year alone. But for investors who believe ubiquitous connectivity is inevitable, AST offers the most direct play on connecting 2.5 billion unconnected people globally.

A quantum's pure play

Quantum computing promises to solve problems classical computers can't touch -- drug discovery, materials science, cryptography, financial modeling. While IBM, Alphabet, and Microsoft run substantial quantum programs within diversified portfolios, Rigetti lives it as a pure-play hardware company.

The company recently announced what it calls the industry's largest demonstrated multichip quantum system using its chiplet-based architecture, a technical milestone that matters more than quarterly earnings at this stage. Second-quarter numbers were weak: Revenue fell 42% year over year to $1.8 million, and the adjusted loss was $0.13 per share. Yet Quanta Computer invested $35 million, providing validation from a Tier-1 manufacturer.

The bear case writes itself: Commercial quantum computing remains years away, IBM and Alphabet have deeper pockets, and cash burn continues with no clear path to profitability. Revenue could stay minimal while development costs climb. That's exactly why the opportunity exists -- markets hate uncertainty, creating asymmetric upside for those betting on 2030, not 2025.

Two moonshots worth buying and holding

Neither AST nor Rigetti belongs in conservative portfolios. These are conviction plays on transformative technologies that could reshape industries or flame out spectacularly.

AST offers nearer-term catalysts with satellite deployments and targeted intermittent U.S. service in late 2025, alongside a ramp-up in government and commercial revenue. Rigetti requires patience, with payoff potentially years away as quantum computing matures. AST around $48 could be cheap if it captures even 1% of the global mobile market. Rigetti in the mid-teens could be a bargain if quantum delivers on its promise later in the decade.

The key is position sizing -- these are portfolio accelerators, not core holdings. For those embracing the risk, both represent genuine innovation at valuations that don't yet price in success. In a market that often overpays for certainty, mispriced innovation can be rare. AST and Rigetti, in turn, could be stellar bargains for investors willing to take the long view.