Elon Musk's SpaceX will need to achieve at least two of its three "moonshots" to justify its huge valuation, a former Tesla board member told CNBC Friday. 

Musk's reusable rocket company is looking to raise $75 billion, selling 555.6 million shares for $135 apiece, according to a filing with the Securities and Exchange Commission. The deal values SpaceX at $1.77 trillion, making it the seventh most-valuable U.S. company, ahead of Tesla.

Venture capitalist and former Tesla board member Steve Westly told CNBC's "Squawk Box Europe" on Friday that pricing SpaceX's imminent IPO is going to be hard to predict, as its three core companies are "completely disparate." 

In addition to its space business, Musk's company owns the Starlink satellite internet service, which accounts for the bulk of its revenue and is the only profitable unit. It also includes xAI, which Musk merged with SpaceX in February.

"SpaceX is three moonshots in one company, but I think they're going to need to make at least two of these moonshots successful to keep that $2 trillion valuation," said Westly, who also founded venture fund, The Westly Group.

SpaceX has achieved its goal of becoming the largest IPO on record.

The number of underlying businesses could expand further still, as speculation builds that Musk could eventually merge Tesla into SpaceX. CNBC reported in May, citing people familiar with the matter, that Tesla and SpaceX already have a laundry list of shared resources, and Musk has discussed with colleagues the possibility of folding the companies together.

Westly told CNBC's Arjun Kharpal that a move to fold Tesla into SpaceX is "absolutely likely."

"It's going to be a tricky one. There will be a lot of governance issues, people will have complaints about that, but… I think there's a good chance that ends up happening," he added.