Author Topic: SpaceX News  (Read 77491 times)

MechAg94

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Re: SpaceX News
« Reply #150 on: February 02, 2021, 03:39:28 PM »
Seems like the landing sequence has no room for error at all.  At least it didn't hit the other one.
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WLJ

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Re: SpaceX News
« Reply #151 on: February 02, 2021, 03:41:13 PM »
Looks like it came from the area of the raptors during the relite
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cordex

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Re: SpaceX News
« Reply #152 on: February 02, 2021, 03:42:05 PM »
Seems like the landing sequence has no room for error at all.
It should eventually have more room for error than the Falcon 9 landing sequence.  The engines on Starship can throttle to the point of allowing hovering.  Falcon 9 can't throttle down that low and so it suicide burns every time.

kgbsquirrel

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Re: SpaceX News
« Reply #153 on: February 02, 2021, 03:44:04 PM »
SN10 you're up
SN10: Wut?

SN9 tried to take a knee after seeing what happened to SN8 but was sent up anyways and went splat.  SN10 must be sweating bullets.  =D

WLJ

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Re: SpaceX News
« Reply #154 on: February 02, 2021, 03:49:31 PM »
SN9 came out leaning and landed leaning
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AZRedhawk44

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Re: SpaceX News
« Reply #155 on: February 02, 2021, 03:53:39 PM »
I think they need to start the maneuver to vertical earlier in their landing regime.  It'll cost a couple more seconds in fuel though, which is supposedly about 600 kilograms per second if the engine is at 100% throttle.

That and they really need those hot gas thrusters.  Control of orientation is just insufficient with cold gas and TVC only.
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kgbsquirrel

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Re: SpaceX News
« Reply #156 on: February 02, 2021, 04:42:31 PM »
I think they need to start the maneuver to vertical earlier in their landing regime.  It'll cost a couple more seconds in fuel though, which is supposedly about 600 kilograms per second if the engine is at 100% throttle.

That and they really need those hot gas thrusters.  Control of orientation is just insufficient with cold gas and TVC only.

Frame it with the requirement for two engine half throttle landing.  Should allow time and altitude for a single engine full throttle burn to safe landing if one engine fails.

WLJ

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Re: SpaceX News
« Reply #157 on: February 02, 2021, 04:47:45 PM »
Frame it with the requirement for two engine half throttle landing.  Should allow time and altitude for a single engine full throttle burn to safe landing if one engine fails.

And/or relight the third
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kgbsquirrel

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Re: SpaceX News
« Reply #158 on: February 02, 2021, 04:53:43 PM »
And/or relight the third

Yup, toss that in the program script, but design the maneuver overall to be achievable on a single engine and after losing the time of running through the other two engines failing.

WLJ

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Re: SpaceX News
« Reply #159 on: February 02, 2021, 04:59:36 PM »
Wonder if they could use a drogue chute to slow it somewhat and give it more time to deal with issues?
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AJ Dual

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Re: SpaceX News
« Reply #160 on: February 02, 2021, 05:03:13 PM »
Wonder if they could use a drogue chute to slow it somewhat and give it more time to deal with issues?

Probably not.

1. It would be a big-*expletive deleted*ss parachute. Here's some people for scale. https://twitter.com/nasaspaceflight/status/1291835348209803264?lang=en
2. It would be an unpredictable dynamic load while it's trying to manuver and balance on it's engines for landing.

Imagine being a tightrope performer who has to hang onto a parachute with one hand, and still maintain their balance.


As to the crash? Not too sad. IIRC, SpaceX crashed roughly 10 Falcon 9's before they started sticking landings consistently.

The only downside was that getting the Falcon 9 to land was "gravy" on an already paying mission that was profitable without recovery and treating it like an expendable rocket.

Probably stings a little more when Starship is meant to be reusable from the get-go. I'd imagine Musk and Co. were only 50/50 on getting a landing out of this test. IIRC, he was like 30/70 for SN8.

And yeah, SN 10 watching... sitting there like...

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dogmush

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Re: SpaceX News
« Reply #161 on: February 02, 2021, 05:04:14 PM »
Wonder if they could use a drogue chute to slow it somewhat and give it more time to deal with issues?

My understanding is they are avoiding chutes so that the same basic maneuver will work on Mars and the moon. With the obvious throttle adjustments.

WLJ

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Re: SpaceX News
« Reply #162 on: February 02, 2021, 05:05:50 PM »
My understanding is they are avoiding chutes so that the same basic maneuver will work on Mars and the moon. With the obvious throttle adjustments.

IIRC most if not all of the Mars landers have used chutes of some sort for slowing. Maybe they could reserve it for landing in 1g for safety sakes
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AJ Dual

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Re: SpaceX News
« Reply #163 on: February 02, 2021, 05:11:24 PM »
I'm not Birdman... but my gut reaction is that the chute would cause more problems than it solves.

And with Starship being roughly the size of the Statue of Liberty.... it's one hell of a parachute.
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WLJ

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Re: SpaceX News
« Reply #164 on: February 02, 2021, 05:12:27 PM »
I'm not Birdman... but my gut reaction is that the chute would cause more problems than it solves.

And with Starship being roughly the size of the Statue of Liberty.... it's one hell of a parachute.

why I said drogue chute, just for slowing it  down a bit and give it more time to sort things out.
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WLJ

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Re: SpaceX News
« Reply #165 on: February 02, 2021, 05:15:46 PM »
Drogue chutes are also used for control
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kgbsquirrel

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Re: SpaceX News
« Reply #166 on: February 02, 2021, 05:19:12 PM »
Any sort of parachute is impractical for this application.

WLJ

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Re: SpaceX News
« Reply #167 on: February 02, 2021, 05:21:25 PM »
I'm just saying to help slow it down a bit to gain a couple of seconds or so of time to sort things out and not to land the thing with. Drogue parachutes are a bit different from normal parachutes
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AJ Dual

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Re: SpaceX News
« Reply #168 on: February 02, 2021, 05:29:28 PM »
Ah. I see what you're saying about a drogue.

The main issue is when you want to deploy it. During the horizontal belly-flop stage? Or right before the pivot and suicide burn? And then cut it loose? Or hang onto it?

I think terminal velocity for Starship as it falls during the belly flop maneuver is about 150mph or so? No idea if that's just for the 10km high test flights, or if that's what it's always expected to be. You'd have to factor in the complexity of the chute with it's "dead weight" that contributes nothing to the launch to see if it's worth it. I'd imagine that SpaceX engineers have considered every angle to chutes for recovery/landing, and found them wanting. 

Fly320's correct me if I'm wrong, but don't commercial airliners come in at about 150-160mph give or take altitude of the airport, weather, and the size/make of the airliner?  Granted it's an angled grazing approach, not straight down... but I don't know if Starship falling at terminal velocity is going to benefit from a chute of any size small or large.

I think they actually have enough "control" over Starship per-se. It's just that the Raptor engines have had unexpected failures so the Starship couldn't actually maneuver the way it's software was telling it to.
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kgbsquirrel

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Re: SpaceX News
« Reply #169 on: February 02, 2021, 05:30:59 PM »
I'm just saying to help slow it down a bit to gain a couple of seconds or so of time to sort things out and not to land the thing with. Drogue parachutes are a bit different from normal parachutes

No.  For many reasons no.

WLJ

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Re: SpaceX News
« Reply #170 on: February 02, 2021, 05:34:19 PM »
No.  For many reasons no.

Why?
All they really do is add a bit of drag and act as an air brake. Please make me aware of what I'm over looking here.
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WLJ

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Re: SpaceX News
« Reply #171 on: February 02, 2021, 05:38:36 PM »
Ah. I see what you're saying about a drogue.

The main issue is when you want to deploy it. During the horizontal belly-flop stage? Or right before the pivot and suicide burn? And then cut it loose? Or hang onto it?

I think terminal velocity for Starship as it falls during the belly flop maneuver is about 150mph or so? No idea if that's just for the 10km high test flights, or if that's what it's always expected to be. You'd have to factor in the complexity of the chute with it's "dead weight" that contributes nothing to the launch to see if it's worth it. I'd imagine that SpaceX engineers have considered every angle to chutes for recovery/landing, and found them wanting. 

Fly320's correct me if I'm wrong, but don't commercial airliners come in at about 150-160mph give or take altitude of the airport, weather, and the size/make of the airliner?  Granted it's an angled grazing approach, not straight down... but I don't know if Starship falling at terminal velocity is going to benefit from a chute of any size small or large.

I think they actually have enough "control" over Starship per-se. It's just that the Raptor engines have had unexpected failures so the Starship couldn't actually maneuver the way it's software was telling it to.

How fast was Apollo moving when they deployed their drogue chute? Note, drogue not the main chutes.
I'm just wondering if it only gain them a couple of seconds to sort out the engine situation that could be the different between life and death for a lot of people.
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kgbsquirrel

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Re: SpaceX News
« Reply #172 on: February 02, 2021, 05:42:27 PM »
Why?
All they really do is add a bit of drag and act as an air brake. Please make me aware of what I'm over looking here.

 *sigh*

It is produces a constantly shifting force vector as it buffets in the turbulent air.
It is largely static in force produced and not variable like the fins.
It will be redundant as the body and fins are already sufficient aerobraking surfaces.
It will act as a large sail for wind causing the craft to roll and translate unpredictably.
It will consume a significant mass fraction in order to be large enough for a vessel of this size.
It will require its own complex deployment system with pyros and mortars to deploy it eating up more mass.
It will be dead weight during most of the mission not providing any ancillary ability (heat radiators in the fins).
...


And that's just what my kerbal flinging amateur rocketry nerd self can come up with.  Imagine SpaceX's list of why they chose no chutes.

So, NO PARACHUTES, capiche?

WLJ

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Re: SpaceX News
« Reply #173 on: February 02, 2021, 05:45:12 PM »
So, NO PARACHUTES, capiche?

So drogue parachutes are okay then?  :P
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kgbsquirrel

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Re: SpaceX News
« Reply #174 on: February 02, 2021, 05:46:01 PM »
So drogue parachutes are okay then?  :P

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