https://www.reddit.com/r/spacex/comments/lw6yk1/notes_from_a...
https://www.spaceflightinsider.com/space-centers/ccafs/autom...
I suppose this classifies as “fail-safe”, though if there’s folks riding on the tip of this large sharp shard with the explosive force of a small nuclear weapon I’d be rather concerned about radio transient interference and things like that.
When passengers are on-board, there’s generally a launch abort engine that is supposed to help them leave safely in a abort scenario
Does Falcon 9 even have a command channel anymore? The trajectory is preprogrammed, guidance and control is automatic, and the flight termination system is automatic as well.
Why the hell does there "got" to be an override. Humans are generally not good at doing hypersonic/supersonic aerodynamic modeling in their heads, especially remotely
I would argue there has "got" to be an override precisely because humans make mistakes all the time and so there's no reason to think that an autonomous failsafe should work in all possible situations.
I don't know much about rocketry, but if it's true that there's no remote abort capability, that seems like a deeply misguided decision.
There you go.
You are welcome to try and disagree with decades of rocket launch practices.
The range safety officer can blow up the rocket if the rocket veers off and is in danger of overshooting the safe area.
Otherwise, you know the reason why we launch over water? Since it doesn't goddamn matter after it clears the tower and clears the danger zone. It either blows up over water, and who cares, it lands in the water, who cares, or it blows up in the upper atmosphere, and who cares.
Also, the rocket blowing itself up is a reference to the fact that if it is going off course, there is damn good chance it will destroy itself since aerodynamic forces are calculated to a specific launch window with upper weather. If not following a calculated path, good chance it will rip itself apart.
Also many abort modes are disabled for the first few seconds in flight so a dumb human or computer wont accidentally trigger a abort after flight starts and blow up the launch pad
>> The range safety officer can blow up the rocket if the rocket veers off and is in danger of overshooting the safe area.
I'm confused. Am I not the one arguing for a remote abort command (which, so far as I know, has been standard practice for a while) and you, above, argue that rockets don't need one because humans are bad at modeling rocket aerodynamics?
What if "missing the drone ship" means "hitting Chicago"?
I'm somewhat surprised to hear that there may not be a functional remote abort mechanism.
It doesn't and never will. The rocket is never on a trajectory that will hit Chicago (or any other populated area). The splashdown point of the ballistic trajectory is always over the ocean, until the final burn puts it on the drone ship or landing pad. If that burn doesn't happen for whatever reason, it crashes in the ocean (and that has happened in the past).
I'm betting that they don't. The reason that this stuff isn't encrypted is likely the same reason that fighter jets and airliners don't have keys. Yes, someone could jump in and do something bad, but the greater danger is the encryption/lock system causing an accident by getting in the way of legitimate commands. This is the launch vehicle, not the spy satellite.
It is likely that physical realities offer sufficient protection. The rocket might be designed to ignore commands coming from the wrong direction and/or signal strength. It might be that to send a command you would have to be physically co-located with the legitimate antenna array, or be ridiculously more powerful, something that would be very easy to detect.
That's just not how encryption works...
Also, a malicious actor being able to point a multi-ton rocket filled with explosive fuel the wrong direction would be far worse than the system continuing the mission autonomously.
Now imagine human spaceflight missions where the command stream can be hijacked by anyone with an SDR. Yeah, not happening.
The command stream better be authenticated, and if you're doing cryptographic message authentication, you might as well encrypt the payload so no one else can read it anyways.
> The rocket might be designed to ignore commands coming from the wrong direction and/or signal strength.
You want to talk about something error prone "getting in the way of legitimate commands"? That would be an unbelievably error prone approach. Oh, the rocket accidentally rolled on its axis a few degrees? Ignore all commands to correct it!
Encryption and authentication are extremely reliable.
An SDR attached to some serious antenna hardware, enough to get into the sidelobe of an antenna pointed at the legitimate command network. As for rockets rolling, that isn't handled by ground commands. That sort of stuff it totally within the rocket's internal systems. The ground staff have very little control until the second stage has done its thing.
I am no expert on spacecraft command channels but I would highly doubt that a lot of non military US spacecraft use encrypted command signals until extremely recently.
He is right. Space engineers are extremely adverse to trying new technology and technique. They are even more adverse to adding code to things that work without adding more code.
In order to talk to one of these things you have to have one of the satellites in the NASA DTN. Technically the DTN protocol supports authentication and encryption but remember that everything about DTN must maintain perfect backwards compatibility with space assets that are made with decades old technology. Security is not it's primary goal like with terrestrial communications. Connectivity is far more important.
So maybe it limits number of adverse actors that can attempt anything, but it doesn't allow you any shortcuts in system design/security.
I've always assumed that frequency barrier stuff was more about defense against tactical, air based electronic jamming/countermeasures.
ETA: Thinking about it some more, what you describe seems like a slightly different type of security by obscurity. If you're relying on it for security.
Given the existence in modern vehicles of:
- a shared bus for communication amongst the processing units
- autonomous emergency braking being fairly standard
and
- network connectivity being available in some cases
I think your analogy might be outdated.