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Comment by alanh | Hacker News Reader

Wow, I hope everyone reads the article before commenting. It’s still amazingly successful. There was a 95% chance the satellite would have made it if they tried, but they were obligated not to try if there were less than a 99% chance of success. (The reduced chance was due to the loss of one of the 9 engines.) And, of course, the primary mission to the space station was fully successful (the engine glitch notwithstanding).

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It wasn't a 95%/99% of the satellite making it; those were the chances that there wouldn't be an incident with the ISS if the upper stage activated.

The Falcon 9 ended up in a slightly different position/velocity than was expected, and the primary mission (deliver to the ISS and don't dare run anything into it) took complete priority over the secondary mission of launching the other satellite into a high orbit.

Article says the opposite:

if there was not at least a 99 percent chance that the rocket had enough fuel to complete the burn

That simply doesn't make sense. The OrbComm satellite was almost sure to burn up if they didn't launch it from a higher orbit. If the only risk was to the satellite, then go high or go home.

The problem was a (very small, almost surely overstated, but there nonetheless) risk to the ISS. From Orbcomm's press release: "the rocket did not comply with a preplanned International Space Station (ISS) safety gate to allow it to execute the second burn."

It's unclear to me what is the risk to ISS. Secondary payload was on the much lower orbit, and even if it was on the same orbital plane, they could just slightly change orbit plane, and try to raise the obit with any chance of success entirely safe for ISS.

It's probably mostly a theoretical risk. On the other hand, I recall a flight to Mir that ended up slamming into the station. And NASA doesn't have any reason to accept a risk that doesn't benefit its operations.

> And NASA doesn't have any reason to accept a risk that doesn't benefit its operations.

Goodwill in the space community and helping to defray costs of future launches by making commercial launches more successful (and thus less expensive, if only for insurance purposes) seem like things that benefit their operations. Perhaps this is a naive opinion, though.

I agree, and I think NASA does too. They're just really conservative about the safety of the ISS (understandably so).

In risk terms, the satellite that was ditched is worth absolutely nothing compared to the ISS. The ISS is the single most important thing humans have in space at the moment.

Purely on the basis that the new trajectory can't be gone over with a pin, even if all the maths comes out saying that everything is lovely, you do not refire an ISS delivery rocket that is not where you expected it to be, especially one that has already sustained damage, just to test a new robot.

And that was why they accepted 99% instead of 99.9% or 99.99%.

There were no flights to Mir that "slammed into the station". The collision on Mir was due to an accident during testing of a new manual docking system for the Progress spacecraft. However, prior to the test the Progress had already successfully docked with the station, the test involved undocking and then switching to a new docking system for the test.

Plane changes are one of the most expensive operations in an orbit iirc.

I agree with your comment. I wanted you to know that I fatfingered the up vote... And gave you a downvote. I apologize.

Here's to many, many more private space successes!

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