The MARSA54 Government Shutdown Sale!

[farsidius]

Thanks again for the sale! Got my order this morning in the mail!

 

[Steve Shannon]

Got my refund!

 

[warnerr]

I am so in! Love my 54- great vendor support- cant wait to add the 33 with accessories onboard a two stage!

 

[jderimig]

Discount today is $30 for altimeter OR 6$ for tilt module. Discount is phasing out day by day. Still a good deal. If you wanted a Marsa now is a good time to buy. Who knows when there will be another government shutdown? Might have to wait another 3 months!

 

[tsai]

Received and started to look at all the goodies. John, the 4 pin header at the top of the Gyro... Is that a pass-through for additional gadgets? Can I use the Marsanet gadget to enable the remote pyro gadgets with the Tilt module all on the same base by daisy chaining the 4-pin headers?

 

[NikeMikey]

Received and started to look at all the goodies. John, the 4 pin header at the top of the Gyro... Is that a pass-through for additional gadgets? Can I use the Marsanet gadget to enable the remote pyro gadgets with the Tilt module all on the same base by daisy chaining the 4-pin headers?

From another thread:
↑
"Will the Marsa Tilt gadget interfere with the ability to use the Marsa Net Gadget, or will you be able to connect both gadgets?"

There will be 2 versions, this one and a wireless Mnet version. So if you do not need the Mnet the wired config will be simpler.

MarsaSystems
jderimig, Nov 5, 2018

 

[jderimig]

Received and started to look at all the goodies. John, the 4 pin header at the top of the Gyro... Is that a pass-through for additional gadgets? Can I use the Marsanet gadget to enable the remote pyro gadgets with the Tilt module all on the same base by daisy chaining the 4-pin headers?

NikeMikey is correct. The 4-pin header on the Gyro is for programming the board in the event of a firmware upgrade.

 

[curtisheisey]

I'm ready for the tilt unit and remote pyro module!!! I am constructing an Upscale Deuce's Wild with two 54 mm motors and two 29mm airstart motors (the latter just for show ... won't do much to this heavy rocket). I 3d printed an enclosure for the rf pyro unit that also servers as motor mount for the 29 mm motors. The 54 motors are canted at 15 degrees, and the 29 motors are canted at 10 degrees. The 54 motors are secured in place by 1/4 aluminum bulkheads that I had water jet cut. I am to have this ready for the April/May MMMSC launches.

 

[jderimig]

Update on orders. Catching up with the orders. A second run of TiltModules were required and may need a third. Orders placed before Jan1 have been mostly shipped. Those who have ordered MrfPyros (Curt) will take a little longer but not much.

Orders placed after Jan 1 should be filled over the next week or so. I appreciate your patience and welcome to all new Marsa family members.

 

[Mendal]

I got mine! Very nicely packed in a box with anti static foam packing. Really looking forward to flying it this season! Thanks

 

[lspikol]

Is there documentation available for the 33 (pdf etc.) and the tilt module?

 

[jderimig]

Is there documentation available for the 33 (pdf etc.) and the tilt module?

User guides on the website.

 

[mikec]

User guides on the website.

I would personally prefer a single PDF file rather than multiple web pages.

Question: for the tilt gadget, does any exceedance of the tilt limit during ascent abort the stage ignition, or is this just checked instantaneously when the other conditions are met?

 

[BradMilkomeda]

I would personally prefer a single PDF file rather than multiple

+1
I like to keep a PDF of my altimeter’s manual on my phone so a can double check operations at a launch.

 

[tim cubbedge]

https://s3.us-east-2.amazonaws.com/marsasystems/MARSA54L+Flight+Computer+User+V1.0.pdf

 

[jderimig]

I would personally prefer a single PDF file rather than multiple web pages.

Question: for the tilt gadget, does any exceedance of the tilt limit during ascent abort the stage ignition, or is this just checked instantaneously when the other conditions are met?

Currently checked when event is due. Planned firmware release to add a rate inhibit to the decision. The tilt module sends rate but the altimeter doesn't process it in the current release

 

[Mendal]

I think one source of confusion might be that the manual for the 33 and the 54 are currently one in the same. John on the webpage I might suggest that you put a note stating that the manual is the same for both altimeters, you might also consider renaming the file so that it lists the 33 in the file name.

 

[mikec]

I think one source of confusion might be that the manual for the 33 and the 54 are currently one in the same.

There's no information about the 33's physical dimensions or how to connect the LCD to it in that manual, so one has no way to know what else might be different, if anything.

I think we can all agree that the documentation needs some work.

 

[jderimig]

I think one source of confusion might be that the manual for the 33 and the 54 are currently one in the same. John on the webpage I might suggest that you put a note stating that the manual is the same for both altimeters, you might also consider renaming the file so that it lists the 33 in the file name.

Will do

 

[jderimig]

I think we can all agree that the documentation needs some work.

Don't know about all but I agree.

 

[mikec]

Don't know about all but I agree.

Since you're the only one whose opinion matters, that's what counts. Thanks!

 

[mikec]

More documentation questions.

1) The timer-mtr setting says "The Timer-Mtr event will not fire if an in-flight anomaly is detected." What kinds of anomalies are detected?

2) The tilt gadget has a wider-range barometric sensor. How does this affect the apogee detection modes? Does "baro only" use this sensor, or does only "kalman" use it? What mode do you recommend for flights above 45K MSL with the tilt gadget present?

 

[curtisheisey]

Hi, what are the hole centers on the
a) MrfBridge and
b) Forthcoming RF Gyro

Is there some sort of a lockout that the rocket has to be ascending for an airstart event. The way I read the manual, you could have the following scenario: At burnout + T, tilt is > threshold which prevents firing. After apogee and parachute deployment, rocket gryo module is point up (depending where mounted), so burnout +T, tilt < threshold, and v < max, so all three conditions are met and you would have a (bad) firing, unless there is some sort of additional lockout condition, either implicit or explicitly programmed. This could be a miniumum velocity for firing, or better yet, rocket has to be ascending.

 

[jderimig]

More documentation questions.

1) The timer-mtr setting says "The Timer-Mtr event will not fire if an in-flight anomaly is detected." What kinds of anomalies are detected?

2) The tilt gadget has a wider-range barometric sensor. How does this affect the apogee detection modes? Does "baro only" use this sensor, or does only "kalman" use it? What mode do you recommend for flights above 45K MSL with the tilt gadget present?

Sorry for the late response, missed the post.
1a. Wild non-monotonic accelerometer readings.
1b. A disagreement between barometric apogee detection versus inertial apogee detect regardless of apogee mode selected. Example one sensor detects apogee before the Mtr-timer event is due.

2. The 100K baro sensor on the tilt is transmitted to the Marsa but not utilized in the current firmware release. A future (soon) altimeter update will use this data to extend the barometric range in both baro and Kalman modes.

 

[jderimig]

Hi, what are the hole centers on the

Is there some sort of a lockout that the rocket has to be ascending for an airstart event. The way I read the manual, you could have the following scenario: At burnout + T, tilt is > threshold which prevents firing. After apogee and parachute deployment, rocket gryo module is point up (depending where mounted), so burnout +T, tilt < threshold, and v < max, so all three conditions are met and you would have a (bad) firing, unless there is some sort of additional lockout condition, either implicit or explicitly programmed. This could be a miniumum velocity for firing, or better yet, rocket has to be ascending.

Good point. There is a lockout based on accelerometer determined speed (100 ft/s) but there a profiles when that could "lie". I see a possible updated firmware push in the near future....

 

[mikec]

I assumed that "AltitudeUp" meant the altitude lockout only applied on ascent. Are you saying there's no checking on this in the current version or just that there's no checking without an altitude lockout?

 

[jderimig]

Altitude up is the condition for starting the timer sequence. It is applied on ascent.

 

[jderimig]

Let me know what specific lockouts you may want to configure and I will put them in the next firmware build.

 

[curtisheisey]

My use case is to airstart a motor shortly after burnout while the rocket is ascending and not tilted. I could live with a any number of possible combinations of conditions. You could pick the one that best aligns with what others want, so you don't have to code them all. There are a lot of corner cases that weasel in in this flight computer business, which can induce very unintended consequences, so thank you for carefully considering all of this.

1)

event triggered if
time > t_burnout + t1 &
angle < maxTilt angle &
speed > speedmin & speed < speedmax

User sets t1 fractional seconds, maxTilt degrees, speedmin ft/s (to be > drogue descent ft/s), and speedmax ft/s. This handles the use case for an airstart after burnout, but rocket is not ballistic or on the drogue.

If you are truly using velocity for the conditional instead of speed, a positive sign would indicate ascent, and a negative sign would indicate descent, assuming ground as a reference. However, having people navigate plus and minus simultaneously with greater than and less than could easily result in errors.



or 2)
event triggered if
time > t_burnout + t1 &
angle < maxTilt angle &
speed < speedmax
& "rocket ascending" (which could be defined in any of a number of different ways)

or
event triggered if
time > t_burnout + t1 &
angle < maxTilt angle &
speed < speedmax &
time < t_burnout + t2

So the event happens within some user specified time window after burnout.

I have a big, heavy, slow rocket, so I can actually live without the "speed < speedmax" term.

Hope this is helpful, and thanks again for your responsiveness.

 

[mikec]

My use case is to airstart a motor shortly after burnout while the rocket is ascending and not tilted.

I would imagine that's close to being everyone's use case. Mine is the same except there is an altitude lockout: time > t_burnout + t1 & angle < maxTilt angle & altitude > min_altitude and rocket ascending. Unless speed is 6DOF-integrated by the tilt gadget to mean "vertical speed" then I've found that the accelerometer-derived speed can be misleading, since the speed could be close to what was expected even if the rocket was flying horizontally; at any rate, I don't plan to use the speed conditions at all myself.

I agree with Curtis that we really don't want a very late and unintended firing when the rocket is descending.