An interesting Buzzfeed article: A “Sneaky” Asteroid Narrowly Missed Earth This Summer. Internal Emails Show How NASA Scientists Totally Missed It. links to the full 176 page FOIA pdf documentcloud.org/documents/…

@Hohmannfan just asked the above, not sure if that's what your comments were about or not

@geoffc I'm not up to date on this

@geoffc I'm much looking forward to seeing the actual performance of the Vinci engine. If meeting expectations, it will make history.

@geoffc Do you have critique of the developments in China? I have the impression that the pace of progress there is comparable to that at SpaceX.

@geoffc Furthermore, are you not critical about SpaceX at all?

I for once think they are downplaying the risk of Kessler syndrome w.r.t. Starlink. Reminds me of climate change deniers. They could prove me wrong if they, e.g., did some actual cleanup of space on the first orbital flights of Starship. Wouldn't it be great if they caught one of those objects that you mentioned to be bound to collide. That could possibly even result in additional public funding.

Noops... I don't have much of a rep anywhere on stackexchange, haha

On the subject of sneaky asteroids, Hale-Bop (the great comet of 1997) had a diameter of 60(!) km and passed through our Neighbourhood at an astoundingly high velocity far exceeding that of any asteroid... Does anyone know if NASA has any plans whatsoever for dealing with the threat of comets???? @uhoh

And you usually only get a couple of months notice with comets

@EverydayAstronaut China is too opaque, govt run, hard to know. They also seem to be taking an 'all of the above' strategy which is pretty good. (Solid based booster, LOX/LH2, Kerosene/LOX, hypergolics).

@EverydayAstronaut Elon runs his mouth off, underestimates the time for everything. But I am enjoying watching them develop.

I think Vinci will be a nice engine, but beyond that not exciting in its current set of use cases.

Kessler Syndrome is real. I do worry about it with Starlink. And their slow response was terrible. However, this is new to them, and it is good it happened now, nothing broke, so they can fix their processes.

Timing is wrong to fix the Genesis/Cosmos issue, but man that would be a cool first flight for Starship. Pick up an old Russian satellite that is out of control and dangerous. And super hard.

ULA Vulcan is a clever old world model. Just not going to work in the current competitive environment.

@HappyKoala I guess in the worst case scenario, the world would agree on launching nukes. Our only hope.

@EverydayAstronaut Assuming nukes would even work. :) The resulting ball of plasma, or pile of rubble vs large singluar mass will likely still hit us. (Odds of diverting to the side, are possible). Or converesly, it will be bad all around, regardless of anyting else.

@geoffc not to forget their sea launching capabilities. Although I assume that is more of a military advantage

Did you read about an idea of a gravity tug? If you had enough time, simply orbit something of sufficient, mass (They suggested only a couple of tons) around the incoming object and gently thrust it away and the object follows, super duper slowly, but if done early enough, possibly cause a sufficient diversion to miss.

@EverydayAstronaut Excellent point as well. That was a bit of a surprise, sort of coming ouot of the blue. I forget, how well sited is the Chinese launch complex? Does China come close to the equator?

@HappyKoala If you post that as a question, I think it will generate several interesting answers. Go for it!

@geoffc Exerting a force requires either a large mass or a large velocity. Since we are sitting in a pretty deep gravity well, we can only do the latter in the form of nukes

The gravity tug idea was clever. If given sufficient time, a small object can drag a larger one a small amount, but over a long enough distance, it can suffice. Very clever. Unsure if it is possible (given warning timelines required, etc...)

@geoffc Right, as a third option to great mass or high velocity, there is decent mass and a lot of time. Apart from typical warning timelines, I think this is difficult to realize seeing how humanity deals with a much more imminent threat, albeit one that is more abstract.

But hey, parking an asteroid around our planet... would make me feel somewhat proud of my species

My car is playing "13 Minutes to the Moon" from the BBC World Service at the moment, and 22 minutes into episode 6 ("Saving 1968") a recorded interview has Michael Collins saying Apollo 8 [as a result of the TLI burn] was the first manned spacecraft to reach escape velocity. Did it? It was the first manned spacecraft to experience gravitational dominance by a body other than the Earth, but escape velocity shouldn't be necessary for that. If so was it to get there (and through VAbs) quicker?

@JCRM See uhoh's last post in this chat ;-)

I'm merely curious, and wondered if anyone knew of the top of their head. I'm not sufficiently interested to do the amount of research required before asking a question.

@geoffc I have to look into that some time. But I know it's not close to the coast. They drop their stages all over the place, and there are pictures of curious villagers near outgasing hypergolic tanks... Anyhow, if it weren't for SpaceX and BlueOrigin, I'd bet on China to win the current space race. They still lag behind somewhat in tech, but their rate of improvement is much higher than with SLS. Also, they already have significant experience (lunar landers, their own space stations, etc.)

@JCRM let me google this for you. Escape velocity from Earth's surface is 11.1 km/s. Wikipedia's TLI page says: "For the Apollo lunar missions, TLI was performed by the restartable J-2 engine in the S-IVB third stage of the Saturn V rocket. This particular TLI burn lasted approximately 350 seconds, providing 3.05 to 3.25 km/s (10,000 to 10,600 ft/s) of change in velocity (delta-v), at which point the spacecraft was traveling at approximately 10.4 km/s (34150 ft/s) relative to the Earth"

@JCRM because the spacecraft was already in orbit and no longer on the surface, this is clearly enough for escape.

what is escape velocity at that altitude?

@JCRM That's the important question. I don't know, but my gut feeling says much less.

11.1 km/s are enough for escape if there's no atmosphere. I think that much more than 1 km/s of that initial velocity would be lost when reaching orbital altitude.

Escape veloicity id about 11.0 km/s at a low Earth orbit of 200 km put tli was at about 345km

No, that's not what escape velocity means

Please enlighten me.

it' the speed you need to be going - it's irrelevenat of atmosphere.

it's the speed at which you need to take off with, after which you shut down engines and there is no drag

in reality you would need more than 11.2 km/s of delta-v to reach escape from the surface of the Earth, because of atmospheric losses, but escape velocity from the surface oft he Earth is 11.2 Km/s

I think we mean the same.

Anyhow, if it is still 11.0 km/s at 200 km altitude, then my gut feeling was wrong. So not sure about the answer to your original question.

they will have been going fairly close to it in any case.

@EverydayAstronaut Sadly, I expect the chinese to surpass the SLS. (I like being proud of the US/western world).

when they copy the N1 design, but improve it so it works @geoffc?

@geoffc Yeah, after all these years of "east" vs "west", there might be new perspectives.

@JCRM Hehe! Would be interesting. But alas, no. N1 was very ambitious and cool. But the wrong way to go today...

multiple small engines not the thing?

@JCRM At the time, 32 engines was a bit much for the state of the art. SpaceX now disagrees, but then they have been flying 9 at a time 70+ times and 27 3 times, so I would argue they have modified the state of the art.

@JCRM multiple big engines the thing 8-)

Really, I wonder how big of an explosion a Super Heavy RUD might be... let me post that as a question

I dunno, NK-33 (NK-15 was the older name) only is 380K lbs. Merlin is 190Klbs or so. So about half the size. Raptor is only 440Klbs. So not really larger or smaller as compared to F-1 at 1.5-1.8MillionLbs.

space.com/…

Genesis and Cosmos missed.

I was wrong. Bigelow has no contact with Genesis II at all anymore, nor does it have a propulsion system. They expect it to renter on its own.

And it was cosmos 3300 which was a spy satellite that worked for 3 months and died.

It too has no contact nor control.