Discussion in 'Off-Topic' started by hobbsyoyo, Sep 13, 2012.
What's a bus in this case?
RTGs? For trans-Neptunian high-rez telescopes? Just throw them up with lightweight nuclear reactors; go the whole field. Ditto with relay sats mid-way to help keep data rates high.
Regenerative braking is not common on satellites and implementing it would turn into a major development program for anyone that went down that path. It's a simple enough concept but it is not actually that easy to implement. And you won't get as much power out of the wheels as you think - a few watts to tens of watts for a few seconds to minutes. This isn't worth the cost to implement in complexity, development time or R&D capital. It will make the bus less reliable and adversely affect the propulsion requirement by inflating propellant needs.
And yes, typically satellites just absorb the waste heat from braking reaction wheels. It's not usually a limiting case for the bus.
I don't really know what you mean by fixed weight cost here. Adding this system will make the satellite less durable - simpler is almost always better.
Are you talking about using solar sails for propulsion? Past Neptune?
Electric propulsion requires huge batteries, huge RTGs or both. It's maybe viable if all you are doing is dumping reaction wheel momentum but it's an iffy trade.
Sorry I threw out random jargon and please continue calling me out on it.
A 'bus' can mean a few things, including:
The body of a satellite, minus extraneous things like solar arrays and antennas
The entire satellite
A section of avionics, either computer interfaces or a voltage rail (power source)
In this instance I meant number 2.
Relays make a lot of sense. I think a nuclear reactor would make sense as well but it's not a sure thing. It would come down to how low you could get your power consumption requirements for the satellite. Lower power favors RTGs as they're smaller and simpler but don't produce a lot of juice.
Falcon Heavy money shots:
Yup but it doesn't have a rocket to go with it. Northrup is allegedly going to launch Pegasus XL rockets from it but they already have their own carrier plane for that so I can't see it being a long-term project. Plus the Pegasus XL is extremely expensive (the cost of an F9 with like 1/50th the lifting capacity) and unreliable. They were supposed to launch one back in Nov or Dec or something and it's still in the hangar as it had issues when they went to launch it.
They were designing their own rockets to make use of the plane's enormous lifting capacity but they cancelled them as soon as Paul G Allen died - which to me is pretty disrespectful of him. Maybe he didn't leave the company enough money to continue with their plans but given his commitment to Stratolaunch and his ongoing health issues before he died, I find it hard to believe.
Video from Egyptsat on-board camera
Ion thrusters working, at 0:54
Very cool video!
The center core of the Falcon Heavy rocket landed successfully but tipped over in rough seas. The top 2/3 of it sheared off and Elon has speculated they might attempt to salvage the engines which are the most expensive part of the rocket.\
Another Chinese start-up mounted a launch attempt and failed. The government is doing their start-up rocket scene a huge favor by offloading ICBM stages on them for testing purposes.
Sounds like some major delays are in store for Demo 2.
I take it the the stages are not fixed to the barge once they are recovered?
They'd have to cool down before they can be secured.
There is a video floating around on twitter that I can't seem to find at the moment -
It looks like they were going to do a static fire of the capsule that was sent to the ISS a couple months back and it exploded. From the video, it appeared the whole thing tore apart. Boeing's surrogates within Congress are going to absolutely murder SpaceX over this and there's now a chance Boeing will get astronauts to the station first. Unless they can show this was an operational error, the investigation and resulting action items are going to take ~6 months to resolve, and the overall delay to their schedule might be close to a year. That's my ball park guess though.
Coincidentally, Boeing had their own pad explosion of their capsule but no footage of it exists and people aren't as hyped about the Starliner as they are Crew Dragon so it flew under the radar. It did cause them significant delays but it was not reported on or talked about to anywhere close to the extent that this Crew Dragon explosion already is.
Usually, they have a robot called the octograbber come out of a little shed on the deck of the barge and it goes out and grabs the booster and secures it. The octograbber is not compatible with Falcon Heavy's center core, however, so it was unsecured. Without the octograbber, they have to send people onto the deck to weld the booster feet to the ship but due to the rough seas, the booster was squirming around and it was unsafe to put people on the deck. I don't think engine cool-down requires very long, I think venting gases and ensuring all valves in their correct state is the main schedule driver. Either way, none of that was the issue here, the hold up was the really rough seas.
Spoiler octograbber :
In other explosive news - that Boeing satellite up in geostationary orbit called Intelsat 29e that was reported to have issues has now been declared a total loss. After the disruption to service, the satellite was shown to have exploded through telescopic observation and there are now several large pieces of it floating about the geostationary arc along with the dead satellite itself.
Sorry, what I meant is that the video of the Boeing test anomaly has not been leaked to the press in the way that the SpaceX failure has. I'm sure video of the Boeing anomaly exists, just not publicly.
Here's a link to leaked video of the SpaceX explosion (twitter won't let me embed it):
This video is the best Easter gift Boeing could have asked for.
I hope this wasn't a COPV* problem. A COPV is what took down the Amos-6 rocket (the on-pad explosion) and NASA has expressed a ton of concern about Falcon's COPVs during their certification for manned flight. If a COPV burst inside Dragon then it will undo a lot of that certification work or at least jeopardize it. I am not sure the Dragon uses COPV's though, it might use (safer, but heavier) all-metal tanks for gas storage.
*carbon overwrapped pressure vessel - bottles used to store high-pressure gases like helium and nitrogen
I’m pretty sure they do have COPVs on Dragon.
China built a Mars simulator in the Gobi desert. They are using it for educational purposes right now and plan to expand it to cover a 67 km2 area.
There are many more cool pictures if you follow the link. Here are a few choice ones:
I like the Stormtrooper armor.
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