totm nov 2023 SpaceX Discussion Thread

[CatastrophicFailure]

They're still managing to keep more-or-less to the two-week cadence so far, this last one was the third in a row without hardware delays.  

[Racescort666]

19 minutes ago, TheEpicSquared said:

Aw. Still, maybe Iridium 11-20 might be able to launch in June, seeing as it's currently slotted in for the 25th. Either way, I think it's a safe bet that Intelsat-35e will be delayed to well after the 1st.

It's worth nothing that Iridium 11-20 is launching from Vandenberg and probably isn't subject to the same butterfly effect type delays that are happening at KSC. I would guess that Iridium 11-20 has a strong chance of launching on time. Also, based off of the previous conversation regarding Florida weather, it's probably less likely to have a weather delay. 

ETA: I'm also wondering if they will start pushing launches to SLC-40 once the pad repairs are complete. I was under the impression that it was supposed to be complete in August and it seems prudent to move F9 operations back there to make the changes to LC-39A to support Falcon Heavy as soon as practical.

Edited June 7, 2017 by Racescort666
Pad speculation

[Skylon]

Is the BulgariaSat first stage booster going to be landed? It's a second flight, hope the launch goes well!

Edited June 8, 2017 by Skylon

[tater]

Yeah, I'd think the second SLC-40 is back they move back there for F9, and then they can finish 39A for FH, as well as crew dragon. At this point schedule pressures really matter, and another SLC-40 incident at 39A would be crippling to progress on FH and crew.

[sevenperforce]

WHOA!

SpaceX is launching the X-37B in August.

This is AWESOME.

42 minutes ago, Skylon said:

Is he BulgariaSat first stage booster going to be landed? It's a second flight, hope the launch goes well!

It's a 4-tonne comsat to GTO so it should be able to easily manage a droneship landing. 

[tater]

2 minutes ago, sevenperforce said:

WHOA!

SpaceX is launching the X-37B in August.

This is AWESOME.

Welcome to 17 hours ago before the thread got derailed  . (page 30?)

[sevenperforce]

Just now, tater said:

Welcome to 17 hours ago before the thread got derailed  . (page 30?)

Dammit.

On another note, I was wondering -- will SpaceX ever lose an RTLS booster?

We've now had five successful RTLS landings, and we know that RTLS is only used when there is plenty of margin; otherwise they just go to a droneship. Every landing has been picture-perfect with plenty of margin. Is this going to be as routine as, say, Shuttle landings?

On yet another note -- the wingspan on the X-37B is 4.55 meters; according to the Falcon 9 User's Guide (page 36), the internal diameter of the payload fairing is just 4.6 meters. That's cutting it awfully close. I wonder if it would launch without the fairing? Might give SpaceX some good aerodynamic modeling validation. Or will they build a specialized fairing for it?

[TheEpicSquared]

12 minutes ago, sevenperforce said:

Dammit.

On another note, I was wondering -- will SpaceX ever lose an RTLS booster?

We've now had five successful RTLS landings, and we know that RTLS is only used when there is plenty of margin; otherwise they just go to a droneship. Every landing has been picture-perfect with plenty of margin. Is this going to be as routine as, say, Shuttle landings?

On yet another note -- the wingspan on the X-37B is 4.55 meters; according to the Falcon 9 User's Guide (page 36), the internal diameter of the payload fairing is just 4.6 meters. That's cutting it awfully close. I wonder if it would launch without the fairing? Might give SpaceX some good aerodynamic modeling validation. Or will they build a specialized fairing for it?

5cm. What could go wrong?  

However I'm thinking they definitely won't launch without a fairing, since the aerodynamic force from the wings would be... destabilizing, to say the least. Also, the payload adapter would generate massive amounts of drag. 

I think they'll just use the standard fairing. There is a 5cm gap to work with. 

[tater]

20 minutes ago, sevenperforce said:

On yet another note -- the wingspan on the X-37B is 4.55 meters; according to the Falcon 9 User's Guide (page 36), the internal diameter of the payload fairing is just 4.6 meters. That's cutting it awfully close. I wonder if it would launch without the fairing? Might give SpaceX some good aerodynamic modeling validation. Or will they build a specialized fairing for it?

The Atlas fairing they have already used is 4.572m internal, to the F9 fairing is actually bigger.

 

http://www.ulalaunch.com/products_atlasv.aspx

Edited June 7, 2017 by tater

[sevenperforce]

6 minutes ago, tater said:

The Atlas fairing they have already used is 4.572m internal, to the F9 fairing is actually bigger.

 

http://www.ulalaunch.com/products_atlasv.aspx

Well there you go. 

The gap looks bigger here:

 

[Skylon]

30 minutes ago, sevenperforce said:

Dammit.

On another note, I was wondering -- will SpaceX ever lose an RTLS booster?

We've now had five successful RTLS landings, and we know that RTLS is only used

On yet another note -- the wingspan on the X-37B is 4.55 meters; according to the Falcon 9 User's Guide (page 36), the internal diameter of the payload fairing is just 4.6 meters. That's cutting it awfully close. I wonder if it would launch without the fairing? Might give SpaceX some good aerodynamic modeling validation. Or will they build a specialized fairing for it?

While I'd love to see a custom fairing, I imagine they would be fine with 5cm, but separation may be hairy. I guess it's worth seeing how the fairing can handle separation with large payloads (dimensions, not mass), though maybe with a less expensive vehicle.

So looks like the BulgariaSat-1 is reusing the Iridium NEXT 1-10 booster, 5 month six after the first flight

Note that the SES-10 booster launched over 11 months after its first flight in April last year

[TheEpicSquared]

1 hour ago, Skylon said:

While I'd love to see a custom fairing, I imagine they would be fine with 5cm, but separation may be hairy. I guess it's worth seeing how the fairing can handle separation with large payloads (dimensions, not mass), though maybe with a less expensive vehicle.

So looks like the BulgariaSat-1 is reusing the Iridium NEXT 1-10 booster, 5 month six after the first flight

Note that the SES-10 booster launched over 11 months after its first flight in April last year

Cutting the time in half.  

Although it should Ben noted that SES-10 was ready to fly on the reused booster by October, it was only the Amos-6 anomaly that delayed it. So I suspect that the booster finished inspections long before the end of 2016, and SpaceX just used the extra time to conduct more tests.

[Racescort666]

1 hour ago, TheEpicSquared said:

5cm. What could go wrong?  

However I'm thinking they definitely won't launch without a fairing, since the aerodynamic force from the wings would be... destabilizing, to say the least. Also, the payload adapter would generate massive amounts of drag. 

I think they'll just use the standard fairing. There is a 5cm gap to work with. 

I'd be interested to know the tolerance stack-up for all of those parts. 25 mm on each side sounds fairly generous to me but maybe that's because I'm used to cars and trucks. At the same time, if you control for your tolerance stack (the payload adapter looks like it's got dowel pins on it which is a good way of controlling alignment) the next thing to worry about is deflection of the payloads/fairing under flight conditions. If anyone wants to speculate how much the payload/fairing deflects under flight conditions, speculate away. 

[Skylon]

The 5cm free is just over 1% of the total room in the fairing

[tater]

It's already launched in a tighter fairing.

[HebaruSan]

I look forward to the X-37B+Falcon9 KSP videos on Youtube. My attempted replica did OK till I relied on SAS to hold attitude during re-entry.

[Nothalogh]

12 hours ago, sevenperforce said:

Anyone care to guess what the debris is that gets kicked across the landing pad?

Likely all that nice fresh paint being burnt off

4 hours ago, HebaruSan said:

did OK till I relied on SAS to hold attitude during re-entry

Never had luck on winged reentry without RCS to maintain attitude

[tater]

2 hours ago, Nothalogh said:

Likely all that nice fresh paint being burnt off

It's coming from the circle painted on---it could be that they slap a new coat of paint on every time, and a chunk delaminated (several coats thick) from the pad substrate.

That or perhaps to keep the circle and X clean, they have them as an adhesive sticker of some kind (thick).

Edited June 8, 2017 by tater

[Brotoro]

That was the Welcome mat flying off.

[sevenperforce]

16 hours ago, HebaruSan said:

I look forward to the X-37B+Falcon9 KSP videos on Youtube. My attempted replica did OK till I relied on SAS to hold attitude during re-entry.

Working on one of those now. Got the design and deadstick landing down; going to see if I can pull off a Minmus landing and then I'll test re-entry. 

12 hours ago, Nothalogh said:

Never had luck on winged reentry without RCS to maintain attitude

I figured out a neat trick for this. Use canards in a V tail as (at least part of) your rear control surfaces. Give the canards the maximum deployment range. During ascent, keep them fixed or give them a little bit of control authority, if you need to. Then, right before re-entry, deploy and lock them upward. This will force your tail up, keeping the center of pressure behind your center of mass, ensuring a nice prograde attitude with a slight AoA. Once you've completed re-entry, deploy and lock them in the opposite direction, pushing your tail down to allow level flight.

The reason this works is that your spaceplane's lift-to-drag ratio is highly airspeed-dependent. At hypersonic speeds, you have almost no lift in comparison to drag, all control surfaces are constantly stalling, and your attitude is dominated by shuttlecock effects. So, you use high drag on the canards to control entry. Once your speed drops and your lift increases, though, stalling disappears and your spaceplane will want to follow prograde, nosing down, so deploying the canards downward in the tail will allow you to remain level (often without any RCS at all) even as you descend unpowered.

It's the same approach used by SpaceShipOne, but using just a couple of canards rather than the gigantic rotating shuttlecock. I can dust off my example spaceplane and show you how it works, if you want.

[Nothalogh]

7 hours ago, sevenperforce said:

Then, right before re-entry, deploy and lock them upward. This will force your tail up, keeping the center of pressure behind your center of mass, ensuring a nice prograde attitude with a slight AoA. Once you've completed re-entry, deploy and lock them in the opposite direction, pushing your tail down to allow level flight.

But I'm trying to do things correctly, and bleed speed off above 50km with a high AoA .

Your plan would keep me stable, but stuff me face first into the soup at over 2km/s

[sevenperforce]

Just now, Nothalogh said:

But I'm trying to do things correctly, and bleed speed off above 50km with a high AoA .

Your plan would keep me stable, but stuff me face first into the soup at over 2km/s

Not in my experience. You get a decent amount of body lift; I said "slight AoA" but it's probably around 10-15 degrees. With body lift, you end up spending longer at high altitudes and bleeding off quite a bit of speed that way. The purpose of the shuttlecock arrangement is to allow you to switch it up once you're in the thicker atmosphere. By that time, you're down to around Mach 2. I was doing it with a dual-thrust-axis VTOL spaceship that didn't even have full-size wings.

I just flew an X-37B via Falcon 9 mission and did the EDL without any RCS. Imgur album going up now.

[sevenperforce]

@Nothalogh @HebaruSan

Here's my imgur album from the X-37B mission on a Tweakscale'd Falcon 9 mission! The booster does an RTLS recovery.

 

[_Augustus_]

1 hour ago, sevenperforce said:

@Nothalogh @HebaruSan

Here's my imgur album from the X-37B mission on a Tweakscale'd Falcon 9 mission! The booster does an RTLS recovery.

 

That X-37B craft is the only decent KSP replica of it I've seen. 

Edited June 8, 2017 by _Augustus_

[sevenperforce]

1 hour ago, _Augustus_ said:

That X-37B craft is the only decent KSP replica of it I've seen. 

Thanks! Hopefully not too bad for my first proper spaceplane.