Side-by-side IPO readiness, funding history, and valuation comparison. Data sourced by TechStackIPO.
Scores, valuations, and signals for SpaceX, Substack, and 370+ companies. 5-min read every Tuesday.
Aerospace and space transportation company. S-1 CONFIRMED filed May 20, 2026 (CIK 0001181412). Roadshow starts June 8, 2026. IPO target June 18–30, 2026. $75B raise at $275B valuation — largest IPO in history. Lead underwriters: Morgan Stanley, Goldman Sachs, JPMorgan. 30% retail allocation. Government contracts: NASA, DoD, Space Force. Starlink: 10M+ subscribers, $10B+ revenue.
| Industry | Aerospace & Defense |
| Stage | Pre-IPO |
| IPO Status | Private |
| Valuation | $275B |
| Total Funding | $11.9B |
| Headquarters | Starbase, TX |
Newsletter publishing platform enabling writers to build paid subscription audiences.
| Industry | Media Technology |
| Stage | Series B |
| IPO Status | Pre-IPO |
| Valuation | $650M |
| Total Funding | $90M |
| Headquarters | San Francisco, CA |
SpaceX is valued at $275B. Substack is valued at $650M. Both valuations are based on the most recent private funding rounds tracked by TechStackIPO.
SpaceX has raised $11.9B. Substack has raised $90M.
SpaceX is currently private. Substack is currently pre-IPO. Track both on TechStackIPO for S-1 filings and IPO announcements.
SpaceX operates in Aerospace & Defense, while Substack operates in Media Technology.
SpaceX is a Aerospace & Defense company valued at $275B with $11.9B raised. Substack is a Media Technology company valued at $650M with $90M raised. See TechStackIPO's full side-by-side comparison for IPO readiness scores, funding timelines, and investor data.
Accredited investors can access pre-IPO shares in SpaceX and Substack through secondary market platforms, pre-IPO funds, and broker-dealer platforms that facilitate private company transactions. TechStackIPO's marketplace section tracks available access options for both companies. Pre-IPO investments carry higher risk and limited liquidity.