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 defense company with proprietary reusable rocket technology. Confidential S-1 filed April 2026 targeting $75B Nasdaq IPO at $1.75T valuation. $20B projected 2026 revenue, $14B EBITDA. Government contracts with NASA and DoD.
| Industry | Aerospace & Defense |
| Stage | Pre-IPO |
| IPO Status | Private |
| Valuation | $1.75T |
| Total Funding | $11.9B |
| Headquarters | Hawthorne, CA |
Newsletter publishing platform enabling writers to build paid subscription audiences.
| Industry | Media Technology |
| Stage | Series B |
| IPO Status | Pre-IPO |
| Valuation | $650M |
| Total Funding | $82.3M |
| Headquarters | San Francisco, CA |
SpaceX is valued at $1.75T. 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 $82.3M.
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 $1.75T with $11.9B raised. Substack is a Media Technology company valued at $650M with $82.3M 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.