Author Topic: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion Thread 1  (Read 593550 times)

Offline Jim

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #1500 on: 01/26/2018 12:22 PM »
IIRC the rain bird sound suppression system was mainly for potential acoustic damage the the Shuttle's tiles and during Apollo water was mainly for cooling...

For Shuttle, it was the payloads

You are both wrong in that you are both only one-third right. The substantial beefing-up of the sound suppression system after STS-1 was due to:

1. Reported damage to the orbiter and anomalies (body flap structural deflection, airframe cracks, tiles [16 lost, 148 damaged], forward RCS strut buckling) from SRB ignition over-pressure.

2. Concern for the payloads (courtesy of data coming from the DFI payload)

3. Reported damage to the mobile launcher (9.1 meter long crack in upper deck due to shuttle drift over the platform with insufficient shielding from SRB accoustics).

All this information is readily available from NASA and other public source.


The primary purpose that sound suppression existed in the first place (before the first launch) was to protect the payloads. 
The 6 rainbirds were installed on the deck of the MLP to blanket the deck with a layer of water.  This was to prevent reflection of sound from the large deck when the vehicle was a few seconds off the pad.  The side mounting location of the orbiter and the payload bay put the payloads in a more vulnerable position to this reflected sound.

Water bags and additional nozzles in the flame ducts for SRB ignition overpressure were added after the first flight.

Offline dglow

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #1501 on: 01/26/2018 12:53 PM »
Jim, you are a veritable KSC historian  thank you.

Offline Rocket Science

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #1502 on: 01/26/2018 01:30 PM »
IIRC the rain bird sound suppression system was mainly for potential acoustic damage the the Shuttle's tiles and during Apollo water was mainly for cooling...

For Shuttle, it was the payloads

You are both wrong in that you are both only one-third right. The substantial beefing-up of the sound suppression system after STS-1 was due to:

1. Reported damage to the orbiter and anomalies (body flap structural deflection, airframe cracks, tiles [16 lost, 148 damaged], forward RCS strut buckling) from SRB ignition over-pressure.

2. Concern for the payloads (courtesy of data coming from the DFI payload)

3. Reported damage to the mobile launcher (9.1 meter long crack in upper deck due to shuttle drift over the platform with insufficient shielding from SRB accoustics).

All this information is readily available from NASA and other public source.
I was going from my old memory not google... Reminds me of some of my students... "Why should I learn things, I'll just look it up"... Ah, the iBrain... :o :(
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Offline starsilk

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #1503 on: 01/26/2018 03:14 PM »
Not the torque issue again... Please watch the last 40 or so F9 flights and see what kind of torque induced rotation you see when the hold-downs release. (hint: none)

I thought its about spin up of the turbo pumps, which is done while the rocket is still hold down (to abort if something goes wrong during this spin up / engine startup). This torque is absorbed by the hold-downs and short lived (lot less than 1sec). So at the moment of release of the hold-downs (>2s after startup) there is not torque anymore to rotate the rocket and you see like you said nothing.

I recall that the first F9 launch exhibited a great deal of rotation directly off the pad. To what cause was this attributed?

AFAIK it was rotational torque from engine startup, exactly as described. they fixed it by pre-canting the engines to counter the torque on the next flight (or, more likely correcting the angle from the predicted roll to the measured roll).

Online speedevil

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #1504 on: 01/26/2018 03:26 PM »
AFAIK it was rotational torque from engine startup, exactly as described. they fixed it by pre-canting the engines to counter the torque on the next flight (or, more likely correcting the angle from the predicted roll to the measured roll).
Do you have a source for this - it seems extraordinarily unlikely that anything other than an INS issue could cause an uncommanded and uncorrected roll and not result in loss of mission.

Offline starsilk

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #1505 on: 01/26/2018 04:03 PM »
AFAIK it was rotational torque from engine startup, exactly as described. they fixed it by pre-canting the engines to counter the torque on the next flight (or, more likely correcting the angle from the predicted roll to the measured roll).
Do you have a source for this - it seems extraordinarily unlikely that anything other than an INS issue could cause an uncommanded and uncorrected roll and not result in loss of mission.

just from memory. if you trawl through this forum for posts following the first F9 launch or before the second you'll find lots of discussion of the roll.

it wasn't uncorrected BTW. it rolled while it cleared the tower then stabilized. vague memory says they had an issue with deliberately not correcting roll for the first few seconds either, which they altered. it's been a long time though..

Offline Nomadd

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #1506 on: 01/26/2018 04:25 PM »
Not the torque issue again... Please watch the last 40 or so F9 flights and see what kind of torque induced rotation you see when the hold-downs release. (hint: none)
I'm pretty sure the rocket wouldn't be released until the engines were going. The whole issue is with startup you know.
« Last Edit: 01/26/2018 04:26 PM by Nomadd »

Online Lars-J

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #1507 on: 01/26/2018 05:20 PM »
Not the torque issue again... Please watch the last 40 or so F9 flights and see what kind of torque induced rotation you see when the hold-downs release. (hint: none)
I'm pretty sure the rocket wouldn't be released until the engines were going. The whole issue is with startup you know.

Obviously. That's what the hold downs are there for, and it can also be countered by a slight gimbal of the engines at startup.

My reaction is more to the "OMG SpaceX might have completely forgotten about startup torque for FH!!!" type of posts. Please - can we at least assume that SpaceX has some degree of competency here?
« Last Edit: 01/26/2018 05:21 PM by Lars-J »

Online Lar

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #1508 on: 01/26/2018 05:29 PM »
I don't think we're discounting competency, we're trying to puzzle out what the issue actually is and guess at how it was solved, as well as guess at exactly what staggered start was actually used.
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Online gongora

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #1509 on: 01/26/2018 05:31 PM »
My reaction is more to the "OMG SpaceX might have completely forgotten about startup torque for FH!!!" type of posts. Please - can we at least assume that SpaceX has some degree of competency here?

I'm not sure what posts you're talking about.  The posts I've seen were just speculating on how they deal with the torque issues since they haven't made any public statements about the startup sequence.

Offline woods170

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #1510 on: 01/26/2018 06:06 PM »
IIRC the rain bird sound suppression system was mainly for potential acoustic damage the the Shuttle's tiles and during Apollo water was mainly for cooling...

For Shuttle, it was the payloads

You are both wrong in that you are both only one-third right. The substantial beefing-up of the sound suppression system after STS-1 was due to:

1. Reported damage to the orbiter and anomalies (body flap structural deflection, airframe cracks, tiles [16 lost, 148 damaged], forward RCS strut buckling) from SRB ignition over-pressure.

2. Concern for the payloads (courtesy of data coming from the DFI payload)

3. Reported damage to the mobile launcher (9.1 meter long crack in upper deck due to shuttle drift over the platform with insufficient shielding from SRB accoustics).

All this information is readily available from NASA and other public source.


The primary purpose that sound suppression existed in the first place (before the first launch) was to protect the payloads. 
The 6 rainbirds were installed on the deck of the MLP to blanket the deck with a layer of water.  This was to prevent reflection of sound from the large deck when the vehicle was a few seconds off the pad.  The side mounting location of the orbiter and the payload bay put the payloads in a more vulnerable position to this reflected sound.

Water bags and additional nozzles in the flame ducts for SRB ignition overpressure were added after the first flight.

Yes, the sound suppression system was there, initially, primarily for the payloads. But that lasted just one launch. The remaining 134 launches the sound suppression system was there for the payload, the vehicle and the launchpad.

System requirements very much can be subject to change one the system starts flying. Shuttle was no different.

Online gongora

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #1511 on: 01/26/2018 06:19 PM »
And we have a target for the launch date:
Launch date, per the current plan:

NET Feb 6th with backup on the 7th.

Launch window each day is 13:30-16:30 EST.

On to Thread 2

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