Author Topic: Spaceport America set for SpaceX reusability testing  (Read 46331 times)

Offline Robotbeat

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Re: Spaceport America set for SpaceX reusability testing
« Reply #60 on: 03/20/2015 11:44 PM »
Number of pins isn't a huge concern. You can use an array of pins to get as many as you like, such as this one from an automatic tool changer.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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Offline Robotbeat

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Re: Spaceport America set for SpaceX reusability testing
« Reply #61 on: 03/20/2015 11:46 PM »
Honestly, the electrical connector is the easy bit of this whole thing.

Something like a self-aligning Magsafe connector with more (and stiffer) pins and a solenoid or servo locking mechanism to ensure a tight fit.


And how small would that connector be without the magsafe feature?  That is my point.
Not that hard. Just have a guide feature (like a funnel for in-air refueling), could be just a simple bevel (depending on how many degrees of freedom you have).

This is just engineering. It's not especially difficult compared to everything else. The real difficulty lies elsewhere (although you would want to spend some resources to ensure you have a well-engineered connector).
« Last Edit: 03/20/2015 11:47 PM by Robotbeat »
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline Robotbeat

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Re: Spaceport America set for SpaceX reusability testing
« Reply #62 on: 03/20/2015 11:51 PM »
But I don't think SpaceX is really talking about totally automated mating of stages and stuff. For simple things like plugging in some cables, no reason not to just have someone there to plug it in (although mechanical mating of the stages probably would benefit from a big jig to make it faster).

I think the auto-refueling idea was mentioned due to the off-handed remark that the first stage would refuel on the unmanned barge and fly back to land. It wasn't about auto-stacking of stages.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline SpunkyEnigma

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Re: Spaceport America set for SpaceX reusability testing
« Reply #63 on: 03/21/2015 01:55 AM »

1. No need for hundreds of pins.  That's got to be historical baggage.  Serialize the data.

2. There's no reason to have the second stage drive the first.  The first is already fully autonomous, has identical avionics, and knows all there is to know.  It can make the same decisions the second stage does, can drop it off within an envelope that the second stage can continue from.  Given that the first stage has to continue flight anyway, I don't see why it has to go through the shock of "switching commanders" on stage separation.  The first stage should be working like a carrier airplane.

This is another case of historical baggage.  An EELV is a single vehicle that's dropping parts until only the upper stage is left.  That's why it's built the way it is.   An F9R is a different type of beast.  A highly reusable first stage that continues flight and RTLS right away, and a an upper stage that even if it comes back, does so much later.  They have different operations cycles, and are their own self-contained entities.  Fewer failure modes this way, too - rockets have been lost because of failure of inter-stage connectors. (can't remember which right now)

<snipped>


Quit with the flippant responses.   It is not historical baggage.  You have nothing to base that assertion on.

1.   for the very many reasons I listed. 

2.  You have been proven wrong on this over and over. How many times do I have say it. Reality is that the second stage controls the first. The first stage is passive until after separation.  That is a fact.

<snipped>

1.  As far as I can tell you only need 2 connections.  One for FTS since you don't trust any other system, and one for data communication.  You'd probably want redundancy of 2 or 3 on this, so we're talking a max of 6 connections with 12 total conductors.  What are we missing?  Power is independent between stages....  I'm at a loss.

2.  Is there any reason why the 1st stage couldn't be in control?  I agree it's a current fact that 2nd stage does, but what is the logic behind it?

Offline Jim

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Re: Spaceport America set for SpaceX reusability testing
« Reply #64 on: 03/21/2015 01:57 AM »

And how small would that connector be without the magsafe feature?  That is my point.
Not that hard. Just have a guide feature (like a funnel for in-air refueling), could be just a simple bevel (depending on how many degrees of freedom you have).

[/quote]

Between the guide feature and the larger pins, how big is the connector now?

Offline Jim

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Re: Spaceport America set for SpaceX reusability testing
« Reply #65 on: 03/21/2015 02:15 AM »

1.  As far as I can tell you only need 2 connections.  One for FTS since you don't trust any other system, and one for data communication.  You'd probably want redundancy of 2 or 3 on this, so we're talking a max of 6 connections with 12 total conductors.  What are we missing?  Power is independent between stages....  I'm at a loss.


There is more, there are staging breakwires, FTS breakwires, telemetry from the first stage to the second, commanding from the second to the first,  some raw data, FTS is more than a few.

Offline deruch

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Re: Spaceport America set for SpaceX reusability testing
« Reply #66 on: 03/21/2015 02:16 AM »
Seems to me the question is, what launch performance can they demonstrate within the ceilings/range authorized from Spaceport America?

Plenty of ceiling, they're okayed up to 100km.  Based on that, I thought they should be able to test/demonstrate almost anything 1st stage related that they wanted.  But, IIRC, they are quite limited on range, something like only 10km (I think I remember reading this in one of the environmental assessments, but I can't find my copy;  will continue to search).  If that's the case, then they mayn't really be able to duplicate actual flight trajectories with much fidelity.  They'd be limited to almost straight up/down launches.  Or, assuming I'm remembering correctly, I'm misreading the limitations and it only means that they have to RTLS within that range?
Shouldn't reality posts be in "Advanced concepts"?  --Nomadd

Offline deruch

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Re: Spaceport America set for SpaceX reusability testing
« Reply #67 on: 03/21/2015 02:18 AM »

1.  As far as I can tell you only need 2 connections.  One for FTS since you don't trust any other system, and one for data communication.  You'd probably want redundancy of 2 or 3 on this, so we're talking a max of 6 connections with 12 total conductors.  What are we missing?  Power is independent between stages....  I'm at a loss.


There is more, there are staging breakwires, FTS breakwires, telemetry from the first stage to the second, commanding from the second to the first,  some raw data, FTS is more than a few.

Ok.  Breakwires aside, is there any reason that the rest couldn't be transmitted wirelessly?
Shouldn't reality posts be in "Advanced concepts"?  --Nomadd

Offline SpunkyEnigma

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Re: Spaceport America set for SpaceX reusability testing
« Reply #68 on: 03/21/2015 02:35 AM »

1.  As far as I can tell you only need 2 connections.  One for FTS since you don't trust any other system, and one for data communication.  You'd probably want redundancy of 2 or 3 on this, so we're talking a max of 6 connections with 12 total conductors.  What are we missing?  Power is independent between stages....  I'm at a loss.


There is more, there are staging breakwires, FTS breakwires, telemetry from the first stage to the second, commanding from the second to the first,  some raw data, FTS is more than a few.

Ok, telemetry and control can be done with just a pair of fiber optics.  Fiber optics could also act as breakwires as well.  Then there is all the wiring that FTS requires.  If SpaceX ever gets approval to not need an independent ordnance based FTS, we're down to just 3 pairs of fiberoptics that can dual duty all telemetry and control plus double use as redundant breakwires.  So other than FTS, I still only see a need for 6 conductors.

What do you mean by raw data, how is that different than telemetry?

Offline SpunkyEnigma

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Re: Spaceport America set for SpaceX reusability testing
« Reply #69 on: 03/21/2015 02:37 AM »

1.  As far as I can tell you only need 2 connections.  One for FTS since you don't trust any other system, and one for data communication.  You'd probably want redundancy of 2 or 3 on this, so we're talking a max of 6 connections with 12 total conductors.  What are we missing?  Power is independent between stages....  I'm at a loss.


There is more, there are staging breakwires, FTS breakwires, telemetry from the first stage to the second, commanding from the second to the first,  some raw data, FTS is more than a few.

Ok.  Breakwires aside, is there any reason that the rest couldn't be transmitted wirelessly?

I think worries of interference would be the greatest concern, followed by energy usage and weight of transmitters and receivers. 

Online meekGee

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Re: Spaceport America set for SpaceX reusability testing
« Reply #70 on: 03/21/2015 02:53 AM »

1. No need for hundreds of pins.  That's got to be historical baggage.  Serialize the data.

2. There's no reason to have the second stage drive the first.  The first is already fully autonomous, has identical avionics, and knows all there is to know.  It can make the same decisions the second stage does, can drop it off within an envelope that the second stage can continue from.  Given that the first stage has to continue flight anyway, I don't see why it has to go through the shock of "switching commanders" on stage separation.  The first stage should be working like a carrier airplane.

This is another case of historical baggage.  An EELV is a single vehicle that's dropping parts until only the upper stage is left.  That's why it's built the way it is.   An F9R is a different type of beast.  A highly reusable first stage that continues flight and RTLS right away, and a an upper stage that even if it comes back, does so much later.  They have different operations cycles, and are their own self-contained entities.  Fewer failure modes this way, too - rockets have been lost because of failure of inter-stage connectors. (can't remember which right now)

3. Look at spacecraft dockings.  Connections are made, after the two heavy bodies mate.  And those are free-flying vehicles.  You can do much better if the bodies are guided.  You can do precision guidance by the jig, or you can have pilot pins and such on the flight hardware.

4. The connectors can be rigidly connected to the master bodies and everything connect at once, or you can have them execute a secondary motion after the mechanical mate.  Either way, if you pre-plan for automation, it's alot easier than if you try to make automation work in a less structured environment.



Quit with the flippant responses.   It is not historical baggage.  You have nothing to base that assertion on.

1.   for the very many reasons I listed. 


You haven't listed any reason for 100s of pins. You've mentioned that the FTS system is wired separately, that's about it.  You're just repeating that "this is how it's done".


2.  You have been proven wrong on this over and over. How many times do I have say it. Reality is that the second stage controls the first. The first stage is passive until after separation.  That is a fact.


Exactly as many times as you have to explain how smaller cheaper satellites are impossible, how SpaceX is about to implode due to internal strife, how reuse is decades away, how the concept of SpaceX doing their own satellite constellation is FanBoi Fantasies, etc.    You call them facts, but in fact they are opinions.

---

I've worked on problems where electrical, pneumatic, and optical connections had to be made across robotic attachments.  I can show you products that do that.  And an industrial robotic environment where cars move on an assembly line at heartbeat of 20 or 40 seconds or so is a lot more demanding than a mating procedure between well-guided and fixtured stages where you have all the time in the world to attach, verify alignment, etc.

Two examples below.

You won't be using them as-is, but it illustrates the point.  Note that they do Pneumatic and even fluid transfer (not sure about hydraulic)

http://www.ati-ia.com/es-MX/company/NewsArticle.aspx?id=386562982
and

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Offline Nomadd

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Re: Spaceport America set for SpaceX reusability testing
« Reply #71 on: 03/21/2015 09:47 AM »
 The ludicrous number of pins could be so a ground crew could access each sensor and control device directly. That would really help in troubleshooting.

Offline jimvela

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Re: Spaceport America set for SpaceX reusability testing
« Reply #72 on: 03/21/2015 10:58 AM »
The ludicrous number of pins could be so a ground crew could access each sensor and control device directly. That would really help in troubleshooting.

That's not how it is done.
Sensors are connected to avionics. Avionics generate telemetry.

I build ground test electronics and launch support equipment.
The first falcon integration and test activities with my systems have already happened.
They're not horribly different from ULA or OATK vehicles in that respect.
Jim is right...


Offline LouScheffer

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Re: Spaceport America set for SpaceX reusability testing
« Reply #73 on: 03/21/2015 11:22 AM »

1.  As far as I can tell you only need 2 connections.  One for FTS since you don't trust any other system, and one for data communication.  You'd probably want redundancy of 2 or 3 on this, so we're talking a max of 6 connections with 12 total conductors.  What are we missing?  Power is independent between stages....  I'm at a loss.


There is more, there are staging breakwires, FTS breakwires, telemetry from the first stage to the second, commanding from the second to the first,  some raw data, FTS is more than a few.
This is a problem in more than just rockets, since connectors are physically large and often the weak link in reliability.  Many military and aerospace applications already addressed this directly by providing multiplexed busses with low pin count.  They are designed for extremely high noise immunity - differential signaling with large signals and no ground connections (transformers or optical coupling). They are also explicitly designed to serve as breakwires - they continuously send null data if they have nothing to say, for a real-time physical connectivity check.  Each physical bus requires 2 pins, so a triple-redundant system needs 6.   These are old and time-tested technologies, used in the F-15, F-16, and F-18, among others.

Examples are MIL-STD-1553 (Defined in http://standards.sae.org/as15531/ , behind a paywall, but see http://www.altadt.com/support/tutorials/mil-std-1553-tutorial-and-reference/ or https://en.wikipedia.org/wiki/MIL-STD-1553 ), the related MIL-STD-1773 (fiber optic), and ARINC 429 (http://www.davi.ws/avionics/TheAvionicsHandbook_Cap_2.pdf or https://en.wikipedia.org/wiki/ARINC_429)

For higher performance, there are military and aerospace implementations of more modern standards such as AS5643, with is a mil spec grade of IEEE-1394b, which is derived from FireWire (see http://standards.sae.org/as5643/ ).  This is used in the F-35, for example.

Offline Jim

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Re: Spaceport America set for SpaceX reusability testing
« Reply #74 on: 03/21/2015 11:35 AM »

How many times do I have say it. Reality is that the second stage controls the first. The first stage is passive until after separation.  That is a fact.


let's try a different way for those who can't understand.

Reality is not what other launch vehicles do.  Reality is how Spacex does it, just as I described.


Online Chris Bergin

Why am I reading pages of posts about pins?

Offline Nomadd

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Re: Spaceport America set for SpaceX reusability testing
« Reply #76 on: 03/21/2015 02:35 PM »
Why am I reading pages of posts about pins?
Because you know that people can only understand how something works by undersanding the most basic details. The great engineers aren't the ones who memorized the manual the best. They're the ones who understand the machine at the gut level because they know how it works down to the pins and switches.
 At least, that's my take after a barrel sized mug of beer in a Tunisian bar and grill.

Online Chris Bergin

Why am I reading pages of posts about pins?
Because you know that people can only understand how something works by undersanding the most basic details. The great engineers aren't the ones who memorized the manual the best. They're the ones who understand the machine at the gut level because they know how it works down to the pins and switches.
 At least, that's my take after a barrel sized mug of beer in a Tunisian bar and grill.

That's cool. But this thread is about the thread title and the article. Perhaps we could concentrate on that here and not get into a few people going on about pins! ;D


Offline llanitedave

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Re: Spaceport America set for SpaceX reusability testing
« Reply #78 on: 03/21/2015 03:21 PM »
I'm on pins and needles wondering how this will end!
"I've just abducted an alien -- now what?"

Online meekGee

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Re: Spaceport America set for SpaceX reusability testing
« Reply #79 on: 03/21/2015 03:43 PM »

How many times do I have say it. Reality is that the second stage controls the first. The first stage is passive until after separation.  That is a fact.


let's try a different way for those who can't understand.

Reality is not what other launch vehicles do.  Reality is how Spacex does it, just as I described.

The question was not how it's done but how it CAN be done to automate things.

SpaceX was looking for engineers to automate the process.  I'm telling you that A) it CAN be done, and B) HOW it can be done.

You keep telling me that in reality it's not done.  But we already know that.

You also keep telling me that it's impossible to be done, cannot be done, because it's not how it's done today.

That's where we differ.
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