Over the last few months we’ve been working on the board designs for our main flight controller, the mini hexcopter esc’s (electronic speed controllers), the vehicle sensor board, and a commercial esc board that shares all of the non-hexcopter-specific functions of our internal esc board but in a more standard rectangular form factor. A lot of time is spent on things like playing around with layout. Here, for your viewing pleasure, is a video of the kind of stuff involved. We thought this was fun just seeing the board tweaked around. Admittedly, this might be a hard-core geek thing, but it made us smile…
Its is sometimes popularly assumed that “we know Mars had an ocean” or “we know Mars had running rivers.” While these ideas have certainly been speculated about, it is far from true that we “know” these things. Several major problems lead to the science community’s uncertainty on how warm and wet early Mars likely was – and hence the uncertainty over whether oceans and true rivers ever existed on Mars. From a climate dynamics perspective, the biggest problem is it is very hard to figure out how Mars could have been warm enough. This is an ongoing problem, but a paper written by our colleague Michael Mischna at JPL and coauthored by researchers at Ashima Research (and using the planetWRF model) looks at how the combination of changes in the planetary tilt, volcanic emission of gases including sulphur dioxide, and differences in surface reflectivity might possibly have allowed liquid water to exist stably on the surface. The uncorrected proof was just put online. We will update this post with a link to the fully-published paper when it becomes available.
Our new paper, out in Icarus, looks at whether numerical models – and specifically our Venus model that is based on the GFDL FMS general circulation model (GCM) – are capable of simulation Venus’ atmospheric circulation. Venus is the most tricky terrestrial atmosphere to properly simulate, and it has variously been suggested that numerical conservation in the models might limit their use. By numerical conservation, we mean the ability of the mathematical representations of the circulation to maintain conserved properties like energy, or in this case, angular momentum (AM). Our Icarus paper looks at the total AM evolution, and how it depends on physical torques (i.e. real stuff) and spurious torques from numerical problems in the dynamics. The attached plot shows the spin-up (from rest) of the Venus atmosphere in the model. The red line shows the total atmospheric value, while the blue line shows the contribution from physics. The “bouncing” of the lines after spinup (about 100 Venus years) represent natural oscillations of AM between the atmosphere and the solid planet and are less than about 5%. That the blue and red lines track so closely shows that the model is gaining almost all of its AM from physically-valid torques – model noise is not dominant or even significant. These kinds of tests are crucial for moving forward to more complete models of Venus’ atmosphere.
We just had a paper describing our “K Distribution Method” (KDM) radiative transfer / heating model for Mars come out it JGR-Planets. The code is a flexible tool that allows arbitrary mixtures of gases and aerosols in the atmosphere to influence the transfer of visible (solar) and planetary thermal photons, and consequently how much the atmosphere heats and cools by these interactions. In other words, how much greenhouse effect is generated and how much the surface is shaded. The KDM is used within our planetWRF Mars global climate and weather model. KDM methods have been used in Earth models for a couple of decades and are now used in a few other planetary models. It greatly increases the flexibility of the model for examining ancient and potentially very different climates on Mars, as well as allowing more accurate investigation of multiple aerosols and gases in the current atmosphere.
One of the things we’re working on with our global Mars atmosphere model (MarsWRF) is predicting martian dust storms. Dust storms on Mars can range anywhere in size from small local events a few kilometers in scale to events that fill the entire global atmosphere. In modeling them, we’re hoping to understand how they develop. The processes we consider in the model are: 1) dust lifting, 2) dust transport and mixing by the winds, 3) dust settling to the surface under gravity, and 4) the heating of the atmosphere as dust absorbs sunlight and interacts with thermal infrared radiation from the planet and atmosphere.
We just published a paper in the journal Icarus (Sept-Oct 2012 edition) on the influence of resolution on global modeling of the Martian atmosphere. The study uses a general circulation model – or global climate model (GCM – take your pick on what the acronym stands for, the definition seems to have changed over time and no one can now agree! ) – this is the same kind of model used to look at things like the large scale atmospheric circulation and climate change on the Earth. In this study, we took a look at how the simulation of the Martian atmosphere changes as the grid spacing (effectively the resolution) changes from about 5 degrees (about 300 km) down to 0.5 degrees (about 30 km). There were a number of interesting findings, including significant changes in the middle and upper atmosphere circulation. In the figure below, surface wind patterns and wind stresses are shown for a 2 degree and a 0.5 degree case. Wind stress is the lateral force (per unit area) felt by the surface due to wind blowing across it. When this stress becomes high enough, sand can get kicked around on the surface and dust lifted. Being a desert planet, dust storms of all sizes play across the Martian surface. A major science question revolves around how these storms form and grow. The resolution test was designed to examine whether there were significant changes in total wind stress with resolution (no) and whether the patterns changed significantly (yes – peak stresses became much sharper and more focused on topography). The paper can be found here in our (Ashima Research’s) publications section.
Here’s a quick image of our miniQuad test article during a static test of the vehicle thrust. We don’t consider the miniQuad a real flight vehicle – it’s a testbed that uses our new modular and integrated ESC / battery / motor (“wing”) boards we showed a couple of months ago; and it drives them with the old centre board from the bigger quad that you can see flying in several of our prior posts. The rest of the structure on this “Franken-vehicle” is the harness needed to couple the old and the new for this temporary test system. The testbed is being used to conduct functional tests and thrust measurements using the new “wing” boards. The next step in the vehicle development will be the new centre boards.
Today we took delivery of our new 3D printer. Bigger print volume, two nozzles. Here come some ESC / battery holders and a hexcopter cover…
So far we had been using a nice little CMOS low-light camera on the quad. However, we also wanted to test and demonstrate the system with a popular off-the-shelf camera. The advantage in this case being that we ought to be able to obtain a live feed at moderate quality over a wifi link (as with the prior system) but also an HD video when we landed and popped out an SD card. Voilà: a quad flight demonstration with a GoPro Hero2. We’ve embedded snippets from our filming from the ground (including some shots of our live feed monitor) on the HD video we recovered from the GoPro after flight. Make sure to crank this sucker to 1080p on the youtube settings and run fullscreen else it won’t seem any different from the earlier videos! (on the flip side, the sound is from the on board, might want to crank that down – these motors really aren’t *that* loud… unless you’re like 10cm from them)
We are updating our Mars panorama WebGL tool to include the latest Mars Science Laboratory (MSL) “Curiosity” panoramas as they get created at JPL. The display system demonstrates some capabilities of WebGL – an API that allows browser-based systems, via HTML5, to directly exploit the power of your system’s graphics card.
Ashima Arts is developing a range of technologies to allow developers to use WebGL more effectively and efficiently. Check out our upcoming presentation at the 2012 OCaml Users and Developers Workshop (Sept. 14, 2012 in Copenhagen, Denmark). The usual caveat is in place that the display tool will not work for some combinations of browsers and graphics cards (and as usual, friends don’t ever let friends use Internet Explorer). In case this doesn’t work on your machine, here’s a youtube video showing the demo running on one of our Mac laptops.