Chinese Space Program (CNSA) & Ch. commercial launch and discussion

[kerbiloid]

Let's hope, they will survive and stay usable.

[SOXBLOX]

Hitting the stage itself with Patriot would do little, but it could definitely take down a couple pressure vessels and engines. Quick! Send over the Army!

Edited May 3, 2021 by SOXBLOX

[sevenperforce]

1 hour ago, SOXBLOX said:

Hitting the stage itself with Patriot would do little, but it could definitely take down a couple pressure vessels and engines. Quick! Send over the Army!

Our ability to kinetic-kill missiles during boost is between 40% and 70%, I believe. The chances that we could actually target and impact the engine cluster directly, particularly in a tumbling stage, is virtually nil.

[SOXBLOX]

3 hours ago, sevenperforce said:

The chances that we could actually target and impact the engine cluster directly, particularly in a tumbling stage, is virtually nil.

I assume you know I mean during reentry?

No, they're actually very high. It'll be coming in at a shallow angle, which makes it easier. Early Patriot systems had trouble with high-angle inbounds. It's larger than a ballistic missile warhead, and might be slower, given that it's not designed to have as little drag as possible. 

With the current practice of firing two or more missiles at a single RV, I think we can safely say it would be hit and destroyed.

If we're trying to hit it while it's still in orbit, I think a SM-3 or two could do it.

[sevenperforce]

1 hour ago, SOXBLOX said:

I assume you know I mean during reentry?

No, they're actually very high. It'll be coming in at a shallow angle, which makes it easier. Early Patriot systems had trouble with high-angle inbounds. It's larger than a ballistic missile warhead, and might be slower, given that it's not designed to have as little drag as possible. 

With the current practice of firing two or more missiles at a single RV, I think we can safely say it would be hit and destroyed.

If we're trying to hit it while it's still in orbit, I think a SM-3 or two could do it.

The question is not whether we can hit it -- I am pretty sure we can hit it because it's pretty big and coming in slow compared to ballistic missiles -- but whether we can hit the engine cluster exactly.

For a nuclear ICBM, the only concern is disabling the warhead. That's why the Nike Sprint and other similar ABMs carried nuclear warheads of their own -- even at quite a distance, a nuclear blast would produce enough trauma and prompt x-rays to the incoming warhead that it would no longer be able to detonate.

The risk of the Long March 5B core stage is an impact to civilian areas by the engines. They are the only thing we know about that is definitely going to frag anything they hit. Unfortunately the only way to blast them into little pieces is to score a DIRECT hit with a high-energy warhead. Hitting any other part of the stage might change the trajectory of the engines but it won't appreciably damage them.

Remember, this is what one of the powerheads from one of Shuttle Columbia's RS-25s looked like when they dug it out of the crater it made:

That's just the preburner and turbopump; the rest of the engine disintegrated on impact. Hence the (substantial) crater. You'd need a direct hit from a shaped-charge warhead to actually break apart an RS-25 preburner. 

The twin YF-77 engines on the Long March 5B core stage are only slightly smaller than an RS-25.

Similarly, here's the impact site from some of Columbia's OMS propellant tanks:

I don't think the Long March 5B core has any hypergolics, so that's good. It does have at least one helium COPV, though, which will ruin anyone's day if it hits them.

[tater]

I'm sorta torn between wanting it to land in the ocean, and wanting to see it reenter (assuming in doing so it then hits some of the largely empty space around here, and not someone's house).

 

[SOXBLOX]

2 hours ago, sevenperforce said:

but whether we can hit the engine cluster exactly.

I thought you said the entire stage would break up, and one fragment would be the engine cluster... In that case, yeah, we could hit it. If not...

[sevenperforce]

3 hours ago, SOXBLOX said:

I thought you said the entire stage would break up, and one fragment would be the engine cluster... In that case, yeah, we could hit it. If not...

We don't know whether the engines will separate from the thrust structure or not. We don't know when in the breakup sequence the stage will break apart. We don't know which part of the hot streaky bits flying through the upper atmosphere at Mach 20 are the engines. So yeah, there's no way we can hit the engines exactly.

3 hours ago, tater said:

I'm sorta torn between wanting it to land in the ocean, and wanting to see it reenter (assuming in doing so it then hits some of the largely empty space around here, and not someone's house).

My son's birthday is that day and I'll be with him in Virginia so I hope we get to watch it zip over the Virginia skies in daylight and dump itself safely in the Atlantic.

[kerbiloid]

As SpaceX is going to refuel on elliptic orbit, it should develop a Catcher Starship.

The Starship chases and overtakes the deorbited thing, then opens its mouth, and extends the catching net (like they use for shrouds).

Then starts softly pushing the falling thing aside, redirecting it to the safe place.

Then the Starship lands, the thing safely crashes.

[SOXBLOX]

20 minutes ago, sevenperforce said:

We don't know which part of the hot streaky bits flying through the upper atmosphere at Mach 20 are the engines.

We actually could tell that. PAC-3 can discriminate between reentering objects of different densities. The engines would stand out, if they were detached. As you say, that's a big "if".

[JoeSchmuckatelli]

I must have missed it - what day is it expected to reenter? 

[RCgothic]

21 minutes ago, JoeSchmuckatelli said:

I must have missed it - what day is it expected to reenter? 

We have no way of knowing it to the day. A tumbling object could hit a denser air patch broadside on and come down pretty soon. Or it may not. The rate of decay is irregular.

Maybe a tracking company like LEO Labs might have a rough idea, but I haven't seen any public figures.

Edited May 4, 2021 by RCgothic

[kerbiloid]

If pierce it with a kinetic warhead. it will be whistling, so they can hear and run away.

[wumpus]

I'd assume that the logic for hitting the thing would be to break it into smaller pieces which would be more likely to burn up in rentry (although the engine is likely to impact in any event, this way it could bring less mass with it).  I'm guessing time is running out to hit it in perigee (so all the pieces will be in an equally unstable orbit) as the more atmosphere it goes through the more erratic the movement.  Perhaps they could hit it as it gets sufficiently deep into the atmosphere that all the parts will come down quickly.

[YNM]

17 hours ago, sevenperforce said:

That's just the preburner and turbopump; the rest of the engine disintegrated on impact. Hence the (substantial) crater. You'd need a direct hit from a shaped-charge warhead to actually break apart an RS-25 preburner. 

I presume you only need to make sure the engine is fully exposed to the re-entry aero on it's own rather than in any sort of slightly protected way with the stage itself.

[sevenperforce]

1 hour ago, JoeSchmuckatelli said:

I must have missed it - what day is it expected to reenter? 

It will impact between 4 AM on May 8 and 2 PM on May 10, EST. It's a large window because it's tumbling but those are the upper and lower bounds based on observed decay rate.

2 minutes ago, YNM said:

I presume you only need to make sure the engine is fully exposed to the re-entry aero on it's own rather than in any sort of slightly protected way with the stage itself.

I feel like a three-tonne engine might get melty during re-entry aero but I can't imagine it melting enough to actually come apart.

[YNM]

18 minutes ago, sevenperforce said:

I feel like a three-tonne engine might get melty during re-entry aero but I can't imagine it melting enough to actually come apart.

At least separating the nozzle would be pretty good... does mean the denser parts of the engine will re-enter much faster (read : higher speed, not necessarily falling faster) though !

Like, on the Shuttle re-entry there were flaps that protects the engine from the heat of re-entry until the whole thing fails. Even then given the way how the engines were stacked perhaps some of them gets to protect the others slightly... Ideally the engines should re-enter each on it's own. Thing is tumbling but idk how whether it'll stabilize on re-entry and in what way...

But idk. Fingers cross on the fireworks, I suppose.

EDIT : Video showing tumbling (green light is green laser) :

 

Edited May 4, 2021 by YNM

[JoeSchmuckatelli]

55 minutes ago, YNM said:

At least separating the nozzle would be pretty good... does mean the denser parts of the engine will re-enter much faster (read : higher speed, not necessarily falling faster) though !

Like, on the Shuttle re-entry there were flaps that protects the engine from the heat of re-entry until the whole thing fails. Even then given the way how the engines were stacked perhaps some of them gets to protect the others slightly... Ideally the engines should re-enter each on it's own. Thing is tumbling but idk how whether it'll stabilize on re-entry and in what way...

But idk. Fingers cross on the fireworks, I suppose.

EDIT : Video showing tumbling (green light is green laser) :

 

That was cool 

 

Remind me how this works?  The craft at perigee is low enough to encounter atmosphere (likely of different densities) which slows it down somewhat - which is why we see the perigee track decline... But this has a greater impact on the apogee which is why it is declining faster...  Given the method of deceleration, will the apogee track have to drop to the perigee altitude before reentry occurs? 

 

 

 

[JcoolTheShipbuilder]

14 minutes ago, JoeSchmuckatelli said:

That was cool 

 

Remind me how this works?  The craft at perigee is low enough to encounter atmosphere (likely of different densities) which slows it down somewhat - which is why we see the perigee track decline... But this has a greater impact on the apogee which is why it is declining faster...  Given the method of deceleration, will the apogee track have to drop to the perigee altitude before reentry occurs? 

 

 

 

no, it just has to drop to the point where a part of its orbit is close enough for reentry, but generally, it will be nearly circular when that happens... but reentry can happen from escape velocity

[JoeSchmuckatelli]

4 minutes ago, JcoolTheShipbuilder said:

no, it just has to drop to the point where a part of its orbit is close enough for reentry, but generally, it will be nearly circular when that happens... but reentry can happen from escape velocity

Right - but doesn't that mean that the apogee needs to be in the atmosphere (to some degree, however slight) to adjust the perigee to hit the planet? 

 

... Or is the perigee enough in the atmosphere to slow it down to...  (God this stuff twists my brain)... 

Edited May 4, 2021 by JoeSchmuckatelli

[JcoolTheShipbuilder]

Just now, JoeSchmuckatelli said:

Right - but doesn't that mean that the apogee needs to be in the atmosphere (to some degree, however slight) to adjust the perigee to hit the planet? 

hmm.. well... if the booster is in atmo just before and just after perigee, the perigee will go down a little bit, and will comparatively make the apogee go down a lot, until it is mostly in atmosphere and decaying faster

[YNM]

52 minutes ago, JoeSchmuckatelli said:

Given the method of deceleration, will the apogee track have to drop to the perigee altitude before reentry occurs? 

I mean it will, much like what you'd see in KSP (the perigee and apogee will switch around) - but the pass that would mean re-entry simply has to have the perigee low enough to encounter atmosphere that's thick enough to turn the apogee inwards and make it the same as the perigee.

We have no idea which orbit will do it since with every pass the apogee and perigee is changed.

[JoeSchmuckatelli]

4 minutes ago, YNM said:

We have no idea which orbit will do it since with every pass the apogee and perigee is changed

I think that is the piece of the picture I was missing / looking for. 

 

If pe and ap are flipping - that looks like what I remember from playing with nearly circular low altitude atmosphere braking reentry in KSP 

[YNM]

4 minutes ago, JoeSchmuckatelli said:

I think that is the piece of the picture I was missing / looking for. 

Yeah. It is an iterative process, sadly being done by the nature itself, we use iteration often enough in computing but this is not our computer and we don't know all the variables.

[sevenperforce]

Looks like drag is pulling the stage down a little faster than expected, narrowing the impact window from about three and a half days down to just two days. It should re-enter at around midnight EST on May 9, give or take 24 hours.

Spain, Portugal, Turkey, and Italy's boot are the only parts of Europe that are in the zone.

All of Africa, Australia, the Middle East, most of China, and Southeast Asia are in the zone.

Mexico, most of South America, and all of the United States south of Michigan are in the zone.