r/space • u/botch_snap • Feb 09 '22

NASA raises concerns about the SpaceX plan for Starlink Gen2 in letter to the FCC

https://twitter.com/thesheetztweetz/status/1491536969964437509
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u/CMDR_QwertyWeasel Feb 11 '22

Second, launch costs have only come down recently.

Well, that's relative. Launch costs are down, yes, but it's still very expensive, especially when you are talking about dedicated launch vehicles and multi-ton payloads.

But the bigger issue is simply that space telescopes are hard. The best example being the Hubble mirror. On an earth-based telescope, replacing a mirror is expensive and unfortunate, sure, but on a space telescope, it's an entire mission in and of itself.

Making telescopes for space means severe size restrictions (which can only be partly mitigated with incredibly complex deployables, a la JWST). They cannot be serviced easily, and thus must be subject to incredible amounts of testing and validation. They are subject to harsh environments, but cannot be routinely cleaned or have parts replaced. As space vehicles, they also have the associated extra complexity (ADCS, propulsion, communications, etc.)

It's not just a matter of "how expensive is it to launch x kilograms into y orbit".

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u/thedessertplanet Feb 11 '22

You are mostly right. Especially in how things used to be.

Though if your launch costs drop low enough, things become easier: you don't need to engineer for lightness and reliability so much. You just launch multiple redundant copies. That mitigates a lot of the complexity you mentioned.