Sending a rocket into space. - Page 1
Forum section: electronics / projects

author: made2hack
author_rank: Frequent Contributor
timestamp: February 15, 2016, 09:42:34 am
content: Hi all,Wanted to share this video from Copenhagen Suborbitals on the design of their onboard computer using an Atmel microcontroller and other design considerations.

author: HAL-42b
author_rank: Frequent Contributor
timestamp: February 15, 2016, 10:16:15 am
content: Sourcing components that won't outgas in space must be very difficult.

author: HAL-42b
author_rank: Frequent Contributor
timestamp: February 15, 2016, 12:23:56 pm
content: Quote from: blueskull on February 15, 2016, 10:27:46 amIt may change the value of the component or break some of them completely.

author: calexanian
author_rank: Super Contributor
timestamp: February 15, 2016, 03:46:06 pm
content: One solution is to pre outgas the parts and then encapsulate the circuits.

author: mackrc1
author_rank: Contributor
timestamp: February 15, 2016, 07:36:39 pm
content: something doesn't feel right about strapping an arduino to a rocket.

author: made2hack
author_rank: Frequent Contributor
timestamp: February 15, 2016, 07:52:43 pm
content: Quote from: mackrc1 on February 15, 2016, 07:36:39 pmwell, to be pedantic, they are not actually strapping the whole arduino. Just using the Atmel chip with their own custom Arduino layout / pcb.

author: cdev
author_rank: Super Contributor
timestamp: February 16, 2016, 06:37:17 am
content: Satellite interiors make extensive use of gold foil and I think one of the reasons is for shielding.

author: cdev
author_rank: Super Contributor
timestamp: February 16, 2016, 06:38:32 am
content: Cats in space

author: mackrc1
author_rank: Contributor
timestamp: February 16, 2016, 08:50:05 pm
content: I feel if you were going out your way to put a rocket into space and design your own flight computer you wouldn't then go and put the arduino boot loader on it.

author: HAL-42b
author_rank: Frequent Contributor
timestamp: February 16, 2016, 08:57:32 pm
content: Definitely not. I doubt the atmel chip is even involved in the realtime loop.

author: m98
author_rank: Frequent Contributor
timestamp: February 16, 2016, 11:08:33 pm
content: Quote from: HAL-42b on February 16, 2016, 08:57:32 pmWhy? I don't see any reason to doubt the reliability of any reasonable uC for such a simple application.

author: HAL-42b
author_rank: Frequent Contributor
timestamp: February 17, 2016, 01:30:42 am
content: Quote from: m98 on February 16, 2016, 11:08:33 pmEngine control + attitude control + sensors + telemetry all in realtime doesn't seem all that simple to me.

author: cdev
author_rank: Super Contributor
timestamp: February 17, 2016, 02:02:19 am
content: It would be interesting to compare the Apollo onboard computer to an Arduino.. seriously, how do they compare?maybe we're being elitist here when the facts - I wouldn't be surprised if the Apollo missions used basically something with the power of an Arduino. I'm pretty sure that was the best they had in 1969 that could fit on a rocket within the weight limitations.Also, remember HAL, in 1969, when the film 2001 was made, they visualized HAL as basically filling an entire room. (Still, I think they got a lot right in that film, they really did their research as to what the next few decades would bring well)

author: HAL-42b
author_rank: Frequent Contributor
timestamp: February 17, 2016, 02:54:21 am
content: Gyroscopes as big as basketballs and accelerometers consisting of a hunk of metal on a spring and a linear pot. And yet it was binary digital, it was not analog and it was not even binary coded decimal.I admit I have a soft spot for fully analog control loops.

author: jt
author_rank: Regular Contributor
timestamp: February 17, 2016, 03:55:49 am
content: Damn, a thread finally within my expertise - but I never know how much I can say because of the ITAR BS!

author: Fungus
author_rank: Super Contributor
timestamp: February 17, 2016, 09:57:18 am
content: Quote from: HAL-42b on February 17, 2016, 01:30:42 amThat's a software problem, not a hardware problem. If the chip can run the software then what's the problem if it's the same chip used in Arduinos or not?Those AVR chips can do alotif you program them right (some of the Arduino libraries are awfully inefficient...)

author: Rerouter
author_rank: Super Contributor
timestamp: February 17, 2016, 10:18:03 am
content: Engine control is On / off for most systems, variable thrust is rare to see apart from larger systems, equally when in free fall, the choice of propellant also gets interesting, as it may not be at the nozzle but rather a blob in the middle of the tank, possibly using the reaction wheels before any maneuvers to shift it to the nozzle,Attitude control is Up at an angle, with some fine control to get the inclination and pre-circularisation apoapse in the right place, quad copter controllers deal with harder tasks than that with an ATmega 328, heck at the velocities involved, it wouldnt be that hard to predict the orbit off gps points alone on the initial ascent,Now telemetry is what you do when all the other bits are idle, even in predicting its final orbit, it will have slabs of time free, as the calculations are well known,

author: made2hack
author_rank: Frequent Contributor
timestamp: March 01, 2016, 10:34:57 pm
content: Quote from: jt on February 17, 2016, 03:55:49 amPlease tell us as much as you can. We won't report you!

author: calexanian
author_rank: Super Contributor
timestamp: March 02, 2016, 03:30:55 am
content: I am surprised that more of the components did not unsolder themselves when directly exposed to that much heat and flame.

author: jt
author_rank: Regular Contributor
timestamp: March 02, 2016, 05:56:43 am
content: QuoteWell links shouldn't hurt. For further reading, other companies/activities using commercial-of-the-shelf components (including Atmel MCUs) for LEO space operations include:Spacecraft and spacecraft hardware vendors:Pumpkin:www.cubesatkit.comTyvak /Terran Orbital:www.terranorbital.com&www.tyvak.comBlue Canyon:www.bluecanyontech.com/portfolio-posts/cubesatsystems/Clyde Space:www.clyde-space.com/Berlin Space:www.berlin-space-tech.comSinclair:http://www.sinclairinterplanetary.com/A few companies with business plans based on this class of hardware:Visible earth observation:www.planet.com/Weather science:www.spire.com/Lightsail propulsion:http://sail.planetary.org/(not actually a business plan)Also more nano-launch vehicles banking on cheaper commercial electronics based avionics for more economical solutions:Garvey Spacecraft:www.garvspace.com/Generation Orbit:www.generationorbit.com/Related University programs:Uof Michigan:http://umcubed.org/Cal Poly SLO:http://polysat.calpoly.edu/Montana State:https://ssel.montana.edu/Related Archived papers & presentations:CubeSat Workshop:http://dww.cubesat.org/index.php/workshops/past-workshopsSmall Sat Conference:http://digitalcommons.usu.edu/smallsat/

author: calexanian
author_rank: Super Contributor
timestamp: March 02, 2016, 06:12:49 am
content: How about in helium balloon satellites at just the edge of space. Come up with a gas ballasting system to keep them at a stable height. Just a sleep deprived thought.

author: Rerouter
author_rank: Super Contributor
timestamp: March 02, 2016, 06:44:31 am
content: seems most balloons only get you to an altitude of about 40km max. at which point, the atmosphere is less than 3% of ground level,Ignoring drag, and assuming you magically have enough thrust to weight to accelerate with minimal gravity losses, your looking at about 7600m/s from a balloon, stealing the planets rotational speed, and a little bump from the wind going in the right direction,If you can pull that off, while making it light enough to float up that high on a balloon, then you can get to space, barely. compared to the norm of about 10,000m/s for a marginal ground landing (larger rockets have lower drag losses)

author: Howardlong
author_rank: Super Contributor
timestamp: March 02, 2016, 06:58:18 am
content: I am part of a team who've put up several satellites, what do you need to know?I'll warn you now though that you will find that if you ask three different rocket scientists the same question you'll get three or more different answers though.In short in LEO if you're prepared to accept the odd glitch using COTS parts can be a reasonable way ahead. Most outgasing will be caught in the thermal vacuum testing anyway, but also it's common to conformally coat boards anyway, which also maitains rigidity for launch (also tested in pre launch shake tests)."The odd glitch" in LEO is usually caught by watchdog timers and the effects usually fairly benign. We see resets once every few months. Our designs also use dual active devices, an MCU for the more computationally complex day to day stuff and a CPLD for a very basic mode where we can still command the spacecraft even if the MCU goes titsup. Using two completely different designs complementing each other also removes common mode failure.As well as one off events ("single event effects") over time there are cumulative effects ("toal ionising dose") which slowly degrades the insulating gate area of MOSFETs, and eventually will render a transistor inoperative. There are many classes of one-off SEEs though. The worst is a single event latchup leading to single event burnout which is catastrophic, where the totem pole transistor pair turn on together causing a short across the supply. This is often unrecoverable. You can mitigate it by introducing current limiting power down in you power supplies but this adds to complexity and it may be too late anyway as the amount of charge in you decoupling caps may have already sealed the fate.One of our team also sent up Strand-1 a few years ago, this was an off the shelf Android phone.So why use COTS parts rather than so-called "space rated" parts? There are several reasons. Cost is the obvious one. Off the shelf parts tend to be far better characterised than limited volume parts. In a lot of cases, it is a valid business decision to have a 90% success rate for 1/4 the cost of a 99% success rate. After all you could send up four times as many and have a better aggregated success rate that way.My area of specialisation is in the comms segment including telemetry, control and transponders, and the RF segments in general. Among other things currently I'm working on the embedded hardware and software for a digital transponder for use with a geostationary satellite scheduled for launch late this year.I'm not in the US so ITAR and EAR have little direct effect on me, but I have to be aware of them. ITAR and EAR keep many non-US citizens in jobs as a result!

author: Howardlong
author_rank: Super Contributor
timestamp: March 02, 2016, 07:08:39 am
content: Q. Why is LEO much more benign than HEO?A. The Van Allen belts (there are two) protect LEOs from most of the harmful ionising radiation.There are modelling programs like creme96 that will model radiation on a given orbit.

author: made2hack
author_rank: Frequent Contributor
timestamp: March 02, 2016, 10:18:39 am
content: Quote from: Howardlong on March 02, 2016, 06:58:18 amWell, I do have a question unrelated to sending something into space. I want to, in the future, time permitting, send up a weather baloon or other type of "craft" that can circumnavigate the earth and send out a Hello World message (or something to that effect) say every hour / minute / second or so.1- So, where do I begin? What I mean is, what would you concieve as a craft? Would a weather baloon work? Will it just simply climb until it pops? Or can I limit it say to 15km or so, just above commercial air ceiling?2 - How can I communicate with it? Either active or passive? Radio? GPS? Voodoo? Is it possible at that distance to have something affordable?3 - How do I know in what direction it will take? Does it just follow the wind? Are there air currents that will make sure the baloon goes around the world?I know my question is vague but perhaps you can point me in the direction of where to start my searches.

author: nctnico
author_rank: Super Contributor
timestamp: March 02, 2016, 10:22:27 am
content: Quote from: cdev on February 16, 2016, 06:37:17 amNo, those are thermal insulation blankets.

author: coppice
author_rank: Super Contributor
timestamp: March 02, 2016, 11:13:46 am
content: Quote from: nctnico on March 02, 2016, 10:22:27 amJust like a MacLaren F1 engine bay.

author: Howardlong
author_rank: Super Contributor
timestamp: March 02, 2016, 04:14:19 pm
content: Quote from: trs80 on March 02, 2016, 10:18:39 amLots of people do high altitude balloons (HAB), although it's not something I've been involved with directly. For launching it is typical to organise NOTAMs.The launches I'm aware of have used circa 433MHz for narrowband telemetry with GPS. Video is captured for later offline perusal rather than having a live feed as far as I know, the link budget will pretty much dictate that. Almost all consumer GPS is useless for space as they have in built limitations disabling them due to altitude, velocity, and/or acceleration.Typically HABs burst by design above a certain altitude so have limited range, but there have been much longer distances achieved.http://www.arhab.orghas a much better treatise than I could ever give. HABs are not my area of expertise I'm afraid.

author: made2hack
author_rank: Frequent Contributor
timestamp: March 02, 2016, 08:42:53 pm
content: Awesome, thanks for the link. I wasn't sure what to search for but this is exactly it.As for commercial GPS, I heard it had built in restrictions for speed / height so it can't be used in a missle system.

author: Howardlong
author_rank: Super Contributor
timestamp: March 02, 2016, 10:36:28 pm
content: Quote from: trs80 on March 02, 2016, 08:42:53 pmThat is true, I believe there are three limiting parameters, but not all need to be implemented to avoid export restrictions. Zarlink used to do an unrestricted chipset. You can buy them off the shelf from the likes of SSTL but it won't be cheap.A coupe of acquaintances of mine from Cambridge University spent two weeks living on coffee and pizza building their own functioning unrestricted GPS while students, I wanted them to market it, but they didn't seem to be interested at the time. They are the same guys who did thishttp://www.telegraph.co.uk/technology/3548363/Teddy-bears-in-space-first-pictures.html