..If you have a non-systematic code (such as your typical convolutional code) then none of your coded data is the same as your input data. Typically, one data bit gives you two coded bits, for a rate 1/2 code. You can use a simple non-FEC decoder to get the data at the receiver, but if you have a single bit error, the output is completely scrambled.
Usage of a block code like Reed-Solomon alone without inner convolutional code is actually kind of rare these days, isn't it ?
I think its a major design flaw to have a switch that turns off FEC that way...
Certainly, just important to note that the fault appears to be in the third party range safety system, according to RL description, not in their own links.
The roll might have been intentional. It is not unusual for smaller rockets to be spin stabilized.
https://twitter.com/RocketLab/status/894451092884410368
The roll was within limits - we're updating parameters and tightening our bounds ahead of flight two.
I don't buy that the roll was intentional. This is a liquid propellant launch vehicle with gimballing engines. It doesn't need spin stabilization. It will be interesting to see what the roll will be like on the next flight.
The roll might have been intentional. It is not unusual for smaller rockets to be spin stabilized.
https://twitter.com/RocketLab/status/894451092884410368
The roll was within limits - we're updating parameters and tightening our bounds ahead of flight two.
I don't buy that the roll was intentional. This is a liquid propellant launch vehicle with gimballing engines. It doesn't need spin stabilization. It will be interesting to see what the roll will be like on the next flight.
They didn't say that it was necessarily intentional, only that it was within limits and that they are attempting to either correct or reduce it. This most likely means the roll was not designed to happen, but wasn't significant enough to cause a failure
The roll might have been intentional. It is not unusual for smaller rockets to be spin stabilized.
https://twitter.com/RocketLab/status/894451092884410368
The roll was within limits - we're updating parameters and tightening our bounds ahead of flight two.
I don't buy that the roll was intentional. This is a liquid propellant launch vehicle with gimballing engines. It doesn't need spin stabilization. It will be interesting to see what the roll will be like on the next flight.
They didn't say that it was necessarily intentional, only that it was within limits and that they are attempting to either correct or reduce it. This most likely means the roll was not designed to happen, but wasn't significant enough to cause a failure
I agree with that. My post was responding to Lars_J's point.
EDIT Add: Other launch vehicles have had uncontrolled roll rates and been at least partially successful. The first F9 launch comes to mind.
Usage of a block code like Reed-Solomon alone without inner convolutional code is actually kind of rare these days, isn't it ?
There are other types of systematic codes, like turbo codes and low density parity check codes (LDPC). Your normal convolutional code can also be used in systematic form. The IRIG 106 telemetry standard specifies an LDPC code.
http://www.wsmr.army.mil/RCCsite/Documents/106-15_Telemetry_Standards/appendixr.pdf
I think its a major design flaw to have a switch that turns off FEC that way, as it is difficult to detect that the switch is in the wrong position. The switch should be UNC/FEC. If the switch is UNC, this is uncoded data without any parity or coding. If you're transmitting coded data, setting the switch to UNC would give garbage out, since the parity bits would be included with the received data. The same would happen if transmitting uncoded data and setting the switch to FEC. You would also get garbage out, allowing you to detect the incorrect switch position.
What a nasty mistake.
Everything looks OK as the system compensates at close range but falls apart as the test proceeds.
On the upside they are saying all the other telemetry looks OK and the fix is basically another item to the pre-launch check list (provided as always no one ticks it off until it's actually been checked of course, the bane of all very long check lists
)
While nothing is ever certain this suggests the big unknowns for the next launch will be stage separation and high altitude engine start, with perhaps more effort to stop it rolling, even slowly.
I think historically tank pressurization has been an issue with early launches of new LV's but Electron seems OK in that area.
Q417 looks to be quite an exciting time for the launch business.
Stage separation and US engines start were successful.
Stage separation and US engines start were successful.
I had not realized the first test had gotten that far before termination.
That does suggest they have a very strong chance of putting a payload in orbit. For a small company on its second launch this is excellent progress.
"...engines in Electron 1st stage performed above targets..."
Would this mean shorter burn time? (even ~7 seconds short)
I wonder if it was these guys RL threw under the bus?
Rocket Lab USA 2017 Contract Update
The Range Safety Telemetry System has been shipped to New Zealand with non-state funds.
Unfortunately, for Rocket Lab they did not have any launches in 2016 so it pushed all the launches to 2017. The 2017 contract is to do what we would have done in 2016, to support them with the RSTS. Eventually they will operate from Mahia by themselves.
KING said AAC has four people on site, getting antennas set up and ready to support the launch vehicle by March 4.
CAMPBELL confirmed Rocket Lab has selected Pacific Spaceport Complex – Alaska as their U.S. polar launch site. He is currently negotiating a contract for launches starting in 2018.
http://akaerospace.com/sites/default/files/minutes/2017%2002%2023%20Board%20of%20Directors%20Minutes.pdf
Usage of a block code like Reed-Solomon alone without inner convolutional code is actually kind of rare these days, isn't it ?
There are other types of systematic codes, like turbo codes and low density parity check codes (LDPC). Your normal convolutional code can also be used in systematic form. The IRIG 106 telemetry standard specifies an LDPC code.
I'm not at all familiar with IRIG or CCSDS, apart from browsing the specs and ref implementation a few times. But looks like switching FEC modes should change the sync markers and thus the receiver shouldn't lock at all ?
I'm not at all familiar with IRIG or CCSDS, apart from browsing the specs and ref implementation a few times. But looks like switching FEC modes should change the sync markers and thus the receiver shouldn't lock at all ?
That's right. However, it looks like they designed the software not to operate that way.
