Clotho Meetings and Notes
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Meeting Schedule and Notes
Preliminary Meeting Nov. 12
Lynn, Diana, Tom, Rocco at Stanford.
First Meeting Nov. 20
Lynn, Diana, Tom, Rob, Jon at Stanford.
Outside Meeting Nov. 24
Lynn, Diana, Tony Strawa at Ames.
Second Meeting Dec. 10
Lynn, Diana, Tom, Rob at Stanford.
First real discussion of parameters and flight possibilities. See photo of board for an idea of what was discussed.
Outside Meeting Dec. 15
Lynn, Diana, Dan Cziczo at AGU.
Dan recommends whole air sampling as a first goal given the constraints.
Third Meeting Dec. 18
Fourth Meeting Jan. 12
Lynn, Rocco, Diana, Tom, Rob at Stanford.
We have flight windows at Black Rock (up to ~250,000 ft (~76 km)) for March, the weekend of July 22nd, and September the week of the 22nd. The first flight (March) won't have a functioning payload, but will have dummy weights to test the rocket, deployment, etc. We'll need a weight estimate.
For smaller flights, under 100,000 ft (~30 km) we can go on within 45 days' notice. This will probably be what we use to test the real equipment.
We'll be hitting the bulk of the atmosphere traveling at Mach 2-3. At 55,000 ft (~16 km) is the tropopause -- on a descent, between 75-55,000 ft (~23-16 km) the atmosphere thickens very rapidly and you'll get a shock wave forming in front of the parachute. We'll need expertise (NASA) on supersonic decelerators.
There are two challenges in building larger (>100,000 ft (~30 km)) rockets: (1) motor harmonics and potential detonation which become trickier as the amount and size of propellant increases, and (2) two-stage binding and separation, which becomes difficult with very high mass and thrust. We would like to tap the available expertise on (1), probably to do the analysis for us or show us a stock configuration.
The payload should be designed to be deployable on any of these rockets at any altitude.
The larger rockets have "active stabilization", or more like "guidance", which consists of four fins on a metal ring controlled by servos. Servos actually aren't bad for applications like that.
Sensor requirements for the environmental monitoring package affect the needed data connections and support from the main systems.
We should be all set to make tests of the science payload on a zeppelin flight -- they have an Experimenter's Pamphlet with the details. We've set a goal to be ready for this in a month.
Fifth Meeting Jan. 19
Lynn, Rocco, Diana, Tom, Rob, Jon, James, Dick at Stanford. This is the first meeting with a formal agenda.
We have multipath tracking (groups with laptops) solved, for the rocket at least.
James is new. Dick is standing in for Wedge. Wedge probably won't be involved until later in the process, as he's more of a hands-on-construction type of guy.
In the future, we'd like to move to less face-to-face and more dial-in meetings so people don't have to take off work. Meeting in later in the day would also help.
We have 4 weekends in a row for the initial flights. (I missed which weekends these were -- do they start on March 22nd?) These will have dummy weights instead of the real instrumentation, but will also include the payload deployment and recovery system.
For the real flights targeting algal blooms, we're looking at early next year.
In the interests of time, we may need to purchase prefab grains (already allotted for in the budget), perhaps nozzles also (glass-filled phenolic that's compressed, $200-300 apiece).
Some discussion of rocket motors. (For a semi-decent explanation of how the ratings work, see Wikipedia -- please update if you have a better source.) Currently we have a cluster of 3 P-motors on the bottom and one on the top, for the second stage. Using an S-motor seems to be of interest.
This is a new airframe, and higher than Mavericks has flown before. This leads to risks in the following areas:
- We have a large booster, which creates very large stresses. (Does the NASA sounding rocket team have any advice?)
- Dynamic/harmonic coupling and grain design, especially with an S-motor. To reduce risks, we'd like to buy a pre-made motor -- basically the same one that's on the Tomahawk cruise missile.
- Recovery system, especially for the payload. To reduce risks, we would like to use a recovery method that's already been tested.
Unfueled, our motor is approximately 350 lb (~160 kg), which coincidentally is exactly equal to three of Diana. But how many grad students of fuel does it require?
We are going to 125,000 feet initially. The three planned flights (for the four consecutive weekends planned above) are at 125k ft (38 km), 175k ft (53 km), and 225k ft (68 km). We can (and pRobably will) also fly the sustainer (second?) stage alone which is 60-70,000 feet (18-21 km). This is a good way to test the instrumentation and deployment/recovery after we've moved beyond the zeppelin stage.
Unanswered question: do we have rights to the video we take on-board?
Ballpark space estimate for the payload is 6 inches in diameter by 24 inches in height (15 cm by 61 cm).
At low altitudes, the air is dense, we're traveling slowly, and it's necessary to force (pull) air through a filter to get small-size particulate sampling, even from the relatively large environmental density we expect. However, at high altitudes, the air is rarefied, we're traveling very fast, and we need to sample far more air to expect to get anything at all back. So what about one payload that uses two different techniques? Instead of having, say, 10 evacuated cylinders, have 5 empty exhausts lined with filters (for high-altitude impaction) and 5 real cylinders (for low-altitude pulling) sharing a common nozzle. You could use a valve array like this one from Scanivalve to direct the nozzle flow into the different cylinders. This is a fantastic idea.
There is a request for more reference papers, especially ones on the biology, to go up on the wiki.
- Done.
Concern is expressed over the fact that the wiki is publicly accessible (and thus perhaps not the best place to be putting things like our meeting notes). James says the mailing list is also accessible through Google (if anyone can verify this, please put up a link). The plan is to create a branch of the wiki that is user-read-only -- perhaps we should get on this sooner rather than later.
- A section for addressing this has been set up at Rocketpedia:Main Page#Privacy.
There followed a discussion on fin design, stage joining/separation housing, where to store and attach the parachute on the airframe, and other such details.
Sixth Meeting Feb.2
Lynn, Rocco, Diana, Tom, Rob, Dick, Yi at Stanford, using this agenda.
We're coming down in the ballpark of 20-30 ft/s when we hit the ground. It's possible to choke (reef?) the parachute (alter its surface area) to control one's descent somewhat.
We've confirmed that the launch rail we were looking at will indeed support what we're doing.
We've found a contact at JPL who will help us look at the hypersonic recovery system used on Mars rover.
We got our money! Now the project needs to be granulated into manageable pieces. Let's look at resources, then break money down into bits to go to people to start spending. The LA project has additional money attached -- it's now separate from the main pot.
Short-Term:
- test airframe: April 2nd - April 12th (Black Rock)
- products & moments of inertia of airframe, etc. needs to be set
- July is where the instrumentation starts coming in
To test just the upper section, we can put an M or an O motor on the upper stage to fly. Right now we will lose track when we get above certain limits (commercial limits?). We can get around this with Novatel, but we'll need to transcode it to NMEA.
We're talking to other folks (not naming names yet) -- there will be press releases soon. Perhaps we can time these to Darwin's 201's birthday!
Tom Rouse is now onboard and is going to help unload some of Tom A.'s responsibility on airframe design, etc.
We need to get oxidizers and powdered metals (e.g. powdered aluminum) on order soon. There's some hoops to jump through with the ATF because people use powdered aluminum to make fireworks, so there's a limit on how much you can order at once.
Yi's update: we really like the new logo, but it needs a little bit more rocket.
If we go with current payload design, we have RC servos or maybe stepper motors; need to talk to Rob. Right now we have 2 high-power pwm/rc channels, 10 channels of 12-bit ADC -- so timing, altitude, etc. will be recorded to an SD card.
BKNO3 is the preferred high-altitude ignition substance; a piccolo (this is presumably not the right spelling, as I can't find any references for it) is the standard military way of doing high-altitude ignition.
Current outstanding issues:
- office space and meeting times
- decelerator design
- wiki and webmaster
At this point, most other people leave and the airframe team has an individual discussion...
Separation occurs at 6-8k feet. The sustainer will be supersonic at that point (we have a 4-second burn), so you want to fire up the sustainer almost immediately so you don't waste the energy punching back through Mach.
You want the stability margin down low so that you don't "weathercock" (twist like a weather vane) into the wind.
Specific impulse (ISP) = thrust per weight of propellant -- if you slow down the burn, you get adulterants in the fuel that kill your ISP.
Nozzles are usually graphite. We're looking at one that has an aluminum bell -- we might melt it (uh-oh).
Powdered aluminum in your fuel increases motor pressure (it gives you an enthalpy boost).
Tripoli doesn't allow steel as a part of the motor, but maybe we could use chro-moly steel for the fin can since it's easier to weld (and doesn't fragment)?
750 psi -> 245 is the isp we're getting, which is pretty darn good.
They have 30 thousandths of clearance on their slip fits (also looking at thermal expansion etc.)...
External temperature range is +120ºF F to -70ºF, you might get up to 170 or 180 degrees if you end up sitting in the sun on the pad for too long. We'll have to look into a thermo-electric cooler / heater around the spectrometer.
Ideally, we'd be able to separate after 20k feet, because after that the air is sufficiently rarified that you don't worry about weathercocking so much; but you don't want to coast too far after separation because you might not be vertical any more (1-2 sec is fine, but 3-4 is pushing it).
