TOKYO — In what may be a first in the space industry, the cost of insuring a major veteran commercial-launch vehicle is so much higher than its two competitors as to raise questions about the rocket’s commercial viability.

Insurance premiums for launches of International Launch Services’ Russian Proton rocket, which satellite operators and insurers say is a necessary third leg for the commercial market — the SpaceX Falcon 9 and the ArianeGroup Ariane 5 being the other two — total about 12% of the insured value.

That compares with 3 . . .

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