Posts by lglethal

Re: China is not a democracy

On the other hand, China is not the one shouting from the roof tops that they're the protector if Freedom and Democracy(tm) either.

Neither is Sweden, but I know which one I'd prefer to live in...

<rant>(Why does everyone equate Democracy and America, it bloody well isnt and we all know it. Why not equate democracy with a real bloody one - Germany, Denmark, Sweden, Australia, for feks sake...) </end rant>

Think of it this way AC, in the build up to landing you can do a lot of things - course corrections, checking hardware, testing software, run simulations, perform tests on earth, etc. But once the lander hits that atmosphere there is literally NOTHING you can do for it. But wait that 7 minutes and hope all of that testing and simulation was right. If that's not Terrifying for the scientists involved I don't know what is. And it's not just the scientists and engineers involved in the landing, all of the instrument scientists and engineers, are waiting to see if their instruments will survive so that they can do the science they want.

Or why don't I put it this way, insight was first conceived about 10 years ago, it's been under design, construction and testing for 5 years. Its cost 800 million dollars, and there are people who have spent 5-10 years working on this and nothing else and whether or not you've just wasted 10 years of your life comes down to a spacecraft 50 million kms away performing flawlessly a series of actions involving heat shields, parachutes and retro rockets, all autonomously where the slightest fuck up week see all of that hard work down the tube and there is nothing you can do about it. You don't consider that Terrifying? Trust me, when it's your instrument - it fucking well is!!!

Re: Losing @ mark l 2

Actually, the best way to stop this sort of nonsense is to put the punishment on the lawyers. The threat of being disbarred, should stop most lawyers from pursuing ridiculous appeals.

Oh right, sorry, lawyers are immune from punishment, because they write the laws in the first place. Silly me forgot that.

Re: Information

Hi Andy,

The mole works like a jack hammer. Basically inside you have a spring loaded cam that gets loaded up and then releases with a sharp shock that drives the Mole down. The rebound is much slower and is damped by the soil friction along the sides of the Mole (the Mole is long and thin for that reason). This basically means that each stroke down embeds you that little bit further into the soil.

It also means that how fast it is, is highly dependant on what the soil is like. I was one of the designers of the Mole, and believe me we spent ages testing in lots of different soils. The Mole is also powerful enough to scrape along concrete blocks provided it doesn't hit dead on.

As for the cable, it's a special type of electrical flat cable, similar to Kapton tape. Very slippy and it has the added job of collapsing the tunnel afterwards - the cable carries a series of heat sensors which we need in contact with the soil, hence why we do that.

Whilst we did as much testing as possible over the last few years, in vacuum Chambers, in different soils, with rocks and the like buried in the soil, its still impossible to know for certain it will work as planned. Mainly because we have no idea what the Martian soil is actually like. To give an analogy, imagine your are asked to drill a hole in a wall, but your only info about the wall is a picture of the wall with a resolution of 1 pixel per 0.5m^2. What drill bit do you take? A masonry bit because most walls in houses are masonry? What if it happens to be steel or wood? What feeds and speeds do you run the drill at? That's basically what we're dealing with with insight

- attempting the difficult in the face of the unknown - fingers crossed!

Re: This seems like a good argument for ion drives

Ion drives unfortunately are pretty useless for the quick thrust you need for orientation and positioning purposes. Ion drives are fantastic for slow but steady acceleration - movement between planets (or Protoplanets in this case) is a perfect case and that's what was used on Dawn. But for orientation it's too little thrust to achieve in any sort of useful time frame the desired results.

To offer an example, your currently doing science pointing instruments at ceres. But you need to change orientation to point the antennas at earth to deliver that science data. With hydrazine thrusters that's work of maybe 15 minutes. Say the transmission takes another 15,and another 15 to get back into science orientation. You've lost at most 45 mins of science time. With ion thrusters you would need at least 2 hour to change orientation in one direction (probably more) and so for the same action you've lost 4 hours 15 mins science days. If you have to do this every day that's 3,5 hours of science time per day lost. The mission will need to be massively longer to account for all of that missing science data. And that means you need more fuel for the ion thrusters, etc, etc. And in the end it just works out way more difficult to do it with ion thrusters. Not to mention the orbital calculations to work out how long you need to apply the ion thrusters for to get into the correct orientation position when you're talking reaction time frames measured in hours. If you under or overshoot with hydrazine, it's a quick fix, just squirt some more with ion you've got another couple of hours to wait.

Hope that explains a bit why we still use chemical thrusters for orientation instead of ion thrusters. :)

Re: I can't get the sensor to fit

It's all well and good to say that but if you do any job a hundred times it stops being a special job, it just becomes step 7b of job 256. And you've got 4 more jobs to do before the end of the day or the boss is going to get pissy with you. And this bloody bracket, which you've complained about half a dozen times but no one listens, is not going in easily. So you just take your hammer and get it to fit easy as pie. And move on to step 7c.

This is how cock ups like this happen. Because people are more worried about the pressure they'll get from managers for missing a deadline. Their manager is a more immediate problem then some future potential problem for some astronauts they'll never meet.

To avoid this, you really need a culture in the workplace where problems and delays are dealt with properly and no blame is put on the worker when they occur. It sounds very much like Roscosmos does not currently have that culture...

Re: Hahaha...

I was visiting Pheonix for work about 10 years back, and my colleagues and i were told by the hotel not to walk in the neighbourhood after dark or in the early morning. The reason - there were apparently 2 serial killers active in the area (competing for a high score apparently). This was confirmed as not a joke by our host company.

Needless to say, we stuck to the bar for the evenings!