totm nov 2023 SpaceX Discussion Thread

[sevenperforce]

23 minutes ago, tater said:

 

Yikes.

[CatastrophicFailure]

1 hour ago, tater said:

So Crew Dragon is cheaper than Soyuz, and Starliner is MORE than Soyuz? How is that a thing? That doesn't count dev costs (and Boeing proposed and got paid ~2X what SpaceX did for dev and the first few launches).

I have words about this. None of which are fit for the forum. 

[magnemoe]

1 hour ago, sevenperforce said:

Liquid rocket stages do a surprisingly poor job of exploding in flight, and particularly out of the atmosphere. Even in Challenger, when the entire external tank ruptured, mixed, and then ignited, the fireball produced only 4-5 psi of overpressure, which did no significant damage to the orbiter. The orbiter broke apart from aerodynamic loads. In order to have an explosion with overpressure, you need to thoroughly mix the reactants, then contain the ignition long enough to form a supersonic propagating wavefront, which results in a detonation.

CRS-7, which was more or less the worst-case scenario for an in-flight failure of a liquid-propellant two-stage booster, had an extremely benign failure with respect to the capsule.

Super Heavy may be problematic in this regard. If a leak formed in the common bulkhead on the pad, the liquid methane and LOX could mix, forming an explosive gel. Its inevitable ignition would be constrained by the cryosteel walls long enough to produce a massive detonation, larger than some tactical nukes. 

This, I long stated that launch escape systems are kind of build overkill, on the other hand then using SRB you can easy get very high trust at least if you don't care about ISP. 
This in regard to an starship escape system. Starship will have an cargo bay as an extra bulkhead, then 20 meter of crew space after that between the tanks and the escape module or upper deck.  

SRB on the other hand is scary. The real danger of enemy hitting your guns or missiles on warships or tanks is not the shells or warheads but the propellant. HMS hood and lots of the UK battlecruisers in WW1 blew up very spectacular because of this. Turret popping on tanks is an thing in many older tanks. The reason why the M1 tank has the long turret is that shells are stored in the back with armored hatches. 
If you can went it its not so much of an deal, an Russian warship, probably just an concept had the missiles on the sides pointing up and a bit out. This would act as protection core of the ship from smaller hits as the missile would just went up. 
Yes you could make an SRB with weak spots, kind of loose the nozzle if something go wrong. 

[sevenperforce]

28 minutes ago, Ultimate Steve said:

If I remember correctly the srbs never ruptured beyond the small opening that caused the strut and tank burn through. If, when the whole thing broke up, the srbs didn't strike the orbiter (they had struck the tank so idk how likely that is) it may have been fine. Granted the shuttle would be exposed to the sides of the srb plumes for a short period of time, but likely not the full on force of an srb firing or exploding.

The failed O-ring caused a pressure drop that decreased the thrust on that booster, requiring the TVC on both the boosters and the SSMEs to gimbal hard to keep the stack flying straight. Only a few seconds longer, and the thrust shortfall would have exceeded TVC correction capability and pinwheel-yawed out of the flight path, causing the same catastrophic breakup.

There was a structure failure in the external tank, likely due primarily to transverse loads, before the crippled SRB fully separated, rotated, and impacted it. The SRB impact to the intertank caused tank failure earlier than it otherwise would have, but only by seconds. You are correct that the SRBs did not rupture, other than the failed one that transected at the failed o-ring. One of the SRBs may have bounced off one of the orbiter's wings, but it was immaterial; the aerodynamic loads shredded the orbiter instantly.

37 minutes ago, Ultimate Steve said:

Another tantalizing thought is if the srb leak had been on the other side of the srb. It wouldn't have burned through anything, it would have just looked alarming and reduced thrust slightly.

The thrust shortfall still would have eventually caused uncontrollable yaw. Also, the hole was widening every moment, so the entire SRB would have eventually separated at the O-ring.

[CatastrophicFailure]

1 hour ago, sevenperforce said:

The thrust shortfall still would have eventually caused uncontrollable yaw. Also, the hole was widening every moment, so the entire SRB would have eventually separated at the O-ring.

@Ultimate Steve so basically, sadly, the only parallel universes where the crew might have survived are those where they went to Skylab on a Big Gemini instead. 

[sh1pman]

You make reusable rockets, you get less money for them, seems totally fair!

Edited November 15, 2019 by sh1pman

[tater]

It's actually worse, since the 287M$ that Boeing just got raises the price to 102M$/seat.

[CatastrophicFailure]

4 minutes ago, tater said:

It's actually worse, since the 287M$ that Boeing just got raises the price to 102M$/seat.

Yeah? Well... at least Boeing’s parachutes work!

 

oh, wait...

[kerbiloid]

Spoiler

3 hours ago, sh1pman said:

You make reusable rockets, you get less money for them, seems totally fair!

The invisible hand of market.
Surprise-surprise. A seller is free to set his price, a customer is free to pay as much as he wants to any seller.

 

Edited November 15, 2019 by kerbiloid

[RCgothic]

I suppose this means that SpaceX will simply bid more in future.

Edited November 15, 2019 by RCgothic

[Lukaszenko]

 

9 hours ago, sh1pman said:

You make reusable rockets, you get less money for them, seems totally fair!

 

Not sure I follow the logic here 

[Wjolcz]

1 hour ago, Lukaszenko said:

 

 

Not sure I follow the logic here 

That's OK.

Edited November 15, 2019 by Wjolcz

[Rakaydos]

1 hour ago, Lukaszenko said:

 

 

Not sure I follow the logic here 

The missing step is, reusable rockets are cheaper to fly.

So it's really, you make cheaper rockets, you get less money for them.

[RCgothic]

Equal compensation for equal service

[kerbiloid]

2 hours ago, Lukaszenko said:

Not sure I follow the logic here 

A Being company makes a rocket spending 100 gold/flight as cost and wants 120 gold/flight as price to get 20 gold as profit.
A Spice company makes a rocket spending 10 gold/flight as cost and wants 110 gold/flight as price to get 100 gold as profit.

A customer can pay either 110 gold/flight or 120 gold/flight.

Should he pay 110 and let the Spice company get 100 gold of profit?
Or should he say: "Dear Spice. Your competitor Being wants just 20 gold of profit, so take this 40 gold (10 for the rocket and 30 as profit) and feel happy that you get more than the Being can even hope. If you are not agreed, go fly yourself, I'll pay 120 gold to the Being, and you can wait for somebody else."

What should the Spice company choose?

Spoiler

"Okay, okay... So, let's discuss 70.

 

Edited November 15, 2019 by kerbiloid

[Jaff]

Isn’t starliner reusable...

 

aren’t boeing saving similar amounts by reusing capsules as space x are by reusing boosters?!

[.50calBMG]

You would think. The way it's being stated though makes it seem like Boeing is still going to be losing money even with the extra funding. They said they needed it just to compete with SpaceX

[tater]

 

19 minutes ago, Jaff said:

Isn’t starliner reusable...

aren’t boeing saving similar amounts by reusing capsules as space x are by reusing boosters?!

Hard to tell. Shuttle was reusable, too. It was certainly cheaper than building a new Shuttle, but it was not cheap. Remember that the only part that has any reuse is the capsule itself. Probably maps to the cargo dragon reuse roughly.

[Jaff]

2 minutes ago, tater said:

 

Hard to tell. Shuttle was reusable, too. It was certainly cheaper than building a new Shuttle, but it was not cheap. Remember that the only part that has any reuse is the capsule itself. Probably maps to the cargo dragon reuse roughly.

of course it’s impossible to nail the numbers down but surely it strikes down the argument that cheap rockets mean you’re not allowed to charge more? 
 

because cheap capsules is the same thing 

[kerbiloid]

57 minutes ago, tater said:

Hard to tell. Shuttle was reusable, too. It was certainly cheaper than building a new Shuttle, but it was not cheap. Remember that the only part that has any reuse is the capsule itself. Probably maps to the cargo dragon reuse roughly.

A related but maybe offtopic question on the reusability.

A docking port holds a several-tens-up-to-hundred tonnes of mass, withstands compression, bending, etc.

Is it known if the docking ports are actually reusable?
Say, Shuttle is known to be reassembled from flight to flight, and some parts (say, engines) were replaced or sometimes exchanged between the shuttles.
Did they reuse the docking port part or replace it?

The same about Dragon, CST (wannabe), etc.

I mean, does it make actually sense to have it integrated and return from orbit rather than jettison it like presumably unreliable on deorbiting?

[Rakaydos]

1 minute ago, kerbiloid said:

A related but maybe offtopic question on the reusability.

A docking port holds a several-tens-up-to-hundred tonnes of mass, withstands compression, bending, etc.

Is it known if the docking ports are actually reusable?
Say, Shuttle is known to be reassembled from flight to flight, and some parts (say, engines) were replaced or sometimes exchanged between the shuttles.
Did they reuse the docking port part or replace it?

The same about Dragon, CST (wannabe), etc.

I mean, does it make actually sense to have it integrated and return from orbit rather than jettison it like presumably unreliable on deorbiting?

Static loads are easy, the trick is to manage the shock loads of the docking itself, without using RCS near the other. Lots of careful trajectory management to softdock at relative speeds below what the docking collar can handle.

Starship refueling is going to say "But what if we COULD use RCS, both of us, as long as we don't actually spray each other." This gives them a lot more ability to manage their momentum and orientation.

[tater]

2 hours ago, Jaff said:

of course it’s impossible to nail the numbers down but surely it strikes down the argument that cheap rockets mean you’re not allowed to charge more? 
 

because cheap capsules is the same thing 

Agreed, it was dumb of NASA to buy that, but you are right.

They should charge the same, and pocket more.

The big issue is that Boeing bid 2X the dev cost of SpaceX, then operationally they are charging around 2X the price per seat (90M was before the 287M add on, which ups the seat cost to 102M vs SpaceX 55M).

If NASA paid 2X to dev reusable, what;s in it for NASA if they get charged 2X for their investment?

[RealKerbal3x]

Do we have any idea when the Dragon IFA test is meant to happen yet?

[CatastrophicFailure]

7 minutes ago, RealKerbal3x said:

Do we have any idea when the Dragon IFA test is meant to happen yet?

December is the last thing I saw, nothing specific beyond that. 

[tater]

There are 2 other launches at least before the end of the year, as well.