Author Topic: SpaceX Falcon 9 - Iridium NEXT Flight 1 DISCUSSION (Jan. 14 2017)  (Read 287287 times)

Offline manoweb

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\but you need base access to go there.

Oh, OK it's inside the base. Only for Air Force members (maybe their family and friends?)
I mistakenly interpreted "Many SpaceXers were in attendance there" as "SpaceX fans"


Offline WHAP

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But, and this was a debate that recurred many times, the "simple controller" model of traditional launch vehicles is a result of the era in which they were designed, and a computational capacity of a gnat.

There is no reason why a flying vehicle designed from scratch in the 21st century would abide by any of those rules, and every time we get a glimpse into how things are done, it's clear that F9 is a lot cleverer then a simple automaton.

That's what I was wondering, if this could be a harbinger of more ground control to come, except would mission control really want or need it? It might add too much complexity to already complex procedures.

It's not a harbinger of "more" ground control, since that implies that there is some, and that isn't true.  Falcon 9 doesn't appear to be any cleverer than "traditional" launch vehicles.  It does "more", because it has the ability to land, but nothing there seems any "cleverer" than a DC-X landing.  For example, neither one was able to recover from a broken landing leg.

I believe people are misinterpreting the quote to assume that there is some ground control.  SpaceX (the upper stage) is sending a signal to the Iridium dispenser.  That's all.
« Last Edit: 01/22/2017 04:11 PM by WHAP »
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Offline meekGee

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But, and this was a debate that recurred many times, the "simple controller" model of traditional launch vehicles is a result of the era in which they were designed, and a computational capacity of a gnat.

There is no reason why a flying vehicle designed from scratch in the 21st century would abide by any of those rules, and every time we get a glimpse into how things are done, it's clear that F9 is a lot cleverer then a simple automaton.

That's what I was wondering, if this could be a harbinger of more ground control to come, except would mission control really want or need it? It might add too much complexity to already complex procedures.

It's not a harbinger of "more" ground control, since that implies that there is some, and that isn't true.  Falcon 9 doesn't appear to be any cleverer than "traditional" launch vehicles.  It does "more", because it has the ability to land, but nothing there seems any "cleverer" than a DC-X landing.  For example, neither one was able to recover from a broken landing leg.

I believe people are misinterpreting the quote to assume that there is some ground control.  SpaceX (the upper stage) is sending a signal to the Iridium dispenser.  That's all.

That would be one hell of a computer, allowing you to recover from a broken leg....

What we know is that both F9 stages have identical avionics, and that F9S1 is capable not only of ballistic flight, but can handle aerodynamic flight through multiple flight regimes (from hypersonic to subsonic), a re-entry burn which coincides with the reentry interface, terminal guidance and landing.

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Offline CyndyC

I believe people are misinterpreting the quote to assume that there is some ground control.  SpaceX (the upper stage) is sending a signal to the Iridium dispenser.  That's all.

What is your source that SpaceX and stage 2 of the Falcon 9 are one and the same?
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Offline WHAP

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I believe people are misinterpreting the quote to assume that there is some ground control.  SpaceX (the upper stage) is sending a signal to the Iridium dispenser.  That's all.

What is your source that SpaceX and stage 2 of the Falcon 9 are one and the same?

The words "I believe" should give you a clue.  Do you believe that SpaceX's primary method of commanding spacecraft separation is via ground commands?  What advantages do you believe this provides over the S2 flight computer, which has the best knowledge of orbital position, the least command latency, and would not be affected by data dropouts from relay spacecraft or ground stations?  Remember, we're only talking spacecraft separation here.  There are a lot of other times when ground command capability would be very useful.
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Offline meekGee

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I believe people are misinterpreting the quote to assume that there is some ground control.  SpaceX (the upper stage) is sending a signal to the Iridium dispenser.  That's all.

What is your source that SpaceX and stage 2 of the Falcon 9 are one and the same?

The words "I believe" should give you a clue.  Do you believe that SpaceX's primary method of commanding spacecraft separation is via ground commands?  What advantages do you believe this provides over the S2 flight computer, which has the best knowledge of orbital position, the least command latency, and would not be affected by data dropouts from relay spacecraft or ground stations?  Remember, we're only talking spacecraft separation here.  There are a lot of other times when ground command capability would be very useful.

The primary mechanism should be self contained, in case of a communication break, but there should be the ability to control from the ground, in case (for example) the orbit achieved is not what was planned.

So basically, S2 should check the final orbit, and if within an envelope - deploy as planned. If not, wait for a phone call.
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Offline Sam Ho

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The primary mechanism should be self contained, in case of a communication break, but there should be the ability to control from the ground, in case (for example) the orbit achieved is not what was planned.

So basically, S2 should check the final orbit, and if within an envelope - deploy as planned. If not, wait for a phone call.
Waiting for a phone call if the injection orbit is wrong would be counterproductive. If the upper stage knows the orbit is wrong, it means it tried to get to the right orbit and failed, so it won't be much help salvaging the mission. By contrast, there's some chance the payload could salvage itself using its onboard thrusters. It can't do that if it's still attached to the upper stage. Furthermore, it can't deploy its solar panels while attached, so it's going to run out of power quickly.

Offline Kaputnik

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Doesn't CRS-1 demonstrate that S2 is prett much autonomous in deciding what to do in the event of anomolies?
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Offline meekGee

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Doesn't CRS-1 demonstrate that S2 is prett much autonomous in deciding what to do in the event of anomolies?
Didn't they decided not to proceed with the next burn due to concerns about ISS?

The programming of S2, IIRC, didn't proceed with the second burn since fuel margins were lower than planned, but SpaceX could have overridden that.

IIRC, there was some bitterness about not being allowed to do the second burn.
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Online ugordan

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Doesn't CRS-1 demonstrate that S2 is prett much autonomous in deciding what to do in the event of anomolies?
Didn't they decided not to proceed with the next burn due to concerns about ISS?

Based on everything we know, it was an autonomous decision programmed into the stage to decide on the burn whether or not the propellant margin measured by the stage allowed for it.

To this very day I have not seen any evidence of any ground commanding of the F9 vehicle, both in burn commands or onboard camera view switching. Preemptive statement that callouts on flight loop like "FTS is safed" do not imply ground commanding.

Offline meekGee

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Doesn't CRS-1 demonstrate that S2 is prett much autonomous in deciding what to do in the event of anomolies?
Didn't they decided not to proceed with the next burn due to concerns about ISS?

Based on everything we know, it was an autonomous decision programmed into the stage to decide on the burn whether or not the propellant margin measured by the stage allowed for it.

To this very day I have not seen any evidence of any ground commanding of the F9 vehicle, both in burn commands or onboard camera view switching. Preemptive statement that callouts on flight loop like "FTS is safed" do not imply ground commanding.
The decision to stop the timeline was automatic.  I think there was a window where they could have started it, but we're not allowed to, due to ISS concerns.
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Offline Jim

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The Falcon 9 has no capability of receiving RF commands except for destruct.  It has nothing to do with computational ability.  The Saturn V did have the ability to receive guidance updates but no other vehicle has this capability.   It is not needed for basic launch vehicles.  Their mission timeline is short.   Also, there likely is no transmitter or ground station in the appropriate locations.

Launch control centers lose "control" at launch.  Launch vehicles have no "Mission Control Centers" controlling them for flight.  Launch vehicle are autonomous.  All control centers that shown during a launch vehicle flight are just monitoring data.
« Last Edit: 01/23/2017 03:11 PM by Jim »

Offline meberbs

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Doesn't CRS-1 demonstrate that S2 is prett much autonomous in deciding what to do in the event of anomolies?
Didn't they decided not to proceed with the next burn due to concerns about ISS?

Based on everything we know, it was an autonomous decision programmed into the stage to decide on the burn whether or not the propellant margin measured by the stage allowed for it.

To this very day I have not seen any evidence of any ground commanding of the F9 vehicle, both in burn commands or onboard camera view switching. Preemptive statement that callouts on flight loop like "FTS is safed" do not imply ground commanding.
The decision to stop the timeline was automatic.  I think there was a window where they could have started it, but we're not allowed to, due to ISS concerns.
I had brought this up before and had to be corrected, because the mass media reports had made it sound like the decision was made in flight to stop the extra burn.

If you go back and find the relevant article on this site, you will see it is clearly stated that the aborted orbit raising burn was due to a pre-programmed constraint, with no ground based ability or desire to override.

The Falcon 9 has no capability of receiving RF commands except for destruct.
From the last time this came up, there was 1 RF link on the first stage that we were unable to determine its purpose. Unless you know the purpose of that link, your statement is a little too strong, as that link may be used to send commands related to recovery/safing for example.

This doesn't change that in this context the 2nd stage does not have ability to receive commands, and deployment and contingencies are pre-programmed. (Which makes sense, because as we saw this time, sat deployment occurred out of range of ground stations almost completely, due to a combination of orbit timing, and issues at 1 ground station.)

Offline matthewkantar

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At 8:20 in the hosted broadcast for the Iridium launch, Lauren Lyons, a systems certification Engineer at SpaceX states: "Once the F-9 gets to the right orbit, SpaceX will send a separation signal to the dispensers deploying the satellites one by one…"

Here is a link:

Matthew

Offline CyndyC

The Falcon 9 has no capability of receiving RF commands except for destruct.  It has nothing to do with computational ability.  The Saturn V did have the ability to receive guidance updates but no other vehicle has this capability.   It is not needed for basic launch vehicles.  Their mission timeline is short.   Also, there likely is no transmitter or ground station in the appropriate locations.

Launch control centers lose "control" at launch.  Launch vehicles have no "Mission Control Centers" controlling them for flight.  Launch vehicle are autonomous.  All control centers that shown during a launch vehicle flight are just monitoring data.

So all that is the case for launch vehicles (thank you, Jim!), but Lauren's statement was that a separation signal would be sent to a brand new invention between the launch vehicle and the satellites, the dispensers. Satellites receive ground commands all the time, so why not a structure so closely aligned with them. The separation signal wouldn't require a ground station if it can be bounced off a satellite, technology the Russians are using with their new ISS vehicles.

Another clue might be Lauren's current job title, at some point changed from Communications [Something] to Systems Certification Engineer. If you or your predecessors had a hand in certifying onboard systems, wouldn't you have specified the signal was originating within one of those systems? Either that or she was over-simplifying the process for the general public.
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Offline meekGee

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I agree There's very little that can be done from the ground during LEO missions, there is certainly more that can be done during GEO or lunar missions.

F9 was built with an eye towards that.

We have no knowledge from SpaceX one way or another.

In the case of Dragon, clearly it can talk with the ground. Do we know if there's a data connection between it and the S2 flight computers?

Sometimes, "don't know" is all we have, and how it's traditionally done may or may not be applicable, because this is a brand new design, especially relevant when it comes to avionics.
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Offline Lar

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Furthermore, it can't deploy its solar panels while attached, so it's going to run out of power quickly.
Is that always true? I would think that once the fairing is gone, for some birds deployment is at least possible... (might not be a good idea)
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Offline Jim

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...... she was over-simplifying the process for the general public.

Bingo


The separation signal wouldn't require a ground station if it can be bounced off a satellite, technology the Russians are using with their new ISS vehicles.


What satellite?  It can't be just anyone.


So all that is the case for launch vehicles (thank you, Jim!), but Lauren's statement was that a separation signal would be sent to a brand new invention between the launch vehicle and the satellites, the dispensers. Satellites receive ground commands all the time, so why not a structure so closely aligned with them.


What new invention?  The guidance system does this for almost all spacecraft.
« Last Edit: 01/23/2017 05:29 PM by Jim »

Offline Jim

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There is no need for any communication regardless if is it LEO, GEO or Lunar.  There isn't anything special about the F9 or Spacex goals that change this.  The basic mission of a launch vehicle is over in 40 minutes or so.  There is not much to change in that time.  Then there is the ability to react to make a change and finally, there is the ability to communicate the change.
« Last Edit: 01/23/2017 05:36 PM by Jim »

Online FutureSpaceTourist

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Quote
Great tool to visualize all our Launch #1 NEXT sats. See them spreading in Plane 6 as they are tested and moved: stuffin.space/?search=2017-0…

https://twitter.com/iridiumboss/status/823597208314511360

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