Ok, I think lofting a rocket via balloon is a rather clunky way of doing things, since the wind will take it where it wills. Hard to log a waiver/flight plan/etc when you don't know where the thing will end up. But it's workable for X-prize attempts like the DaVinci and others (I'm talking just the concept, not the reality). Also JP Aerospace is looking at a similar, and better IMHO, way to do the same thing. Since "they" can do this legally without causing the FAA a coronary, I'm kinda curious as to what might need to be in place to make such a launch system legal within the bounds of amatuer rocketry. Please don't quote chapter and verse legalese, I never learned Greek. Plainspeak will do just fine since it's just a curiousity being answered.
plan/etc when you don't know where the thing will end up.
The same ones that got hired by the same ones we voted in. Scary, huh? Ok, the FAA likes balloon lofted rockets. But there's a tad more to it than just that, yes? JP Aerospace, for example, is talking about a P size motor going into their rocket and lighting it off at 100-140K up. Something says at that altitude even an "A" motor might be something the FAA would think bore watching a tad closer.
plan/etc when you don't know where the thing will end up.
As long as you light the rocket above 60,000 ft, you should be fine. Technically, 60,000ft is uncontrolled airspace, at least in FAA parlance, and in most locales. You would need a NOTAM to launch the balloon. All this is in the FAR 101's (same as rocketry). You may need a waiver to launch the balloon depending on where you launch from.
We've actually attempted a rockoon flight twice with small estes models, never expecting to get them back, and not having all that much success on either flight. One we lost sometime before ignition (the Jet Stream was wicked that day) the other was a successful launch, but rather low (the video was interesting to see the puff from ignition, then no more rocket...).
Generally, the FAA wants to know when you launch the balloon, when it breaks 60,000 ft (so they can stop caring) and sometimes when it goes below 60,000 ft on the way down. It all depends on how good a relationship you have with your ATC people, and what kind of mood they're in when you request the NOTAM. We've done 27 successful balloon flights, and only one of them required a waiver (a research project that required us to launch inside the city of Grand Forks).
The regs even allow for balloon flights without NOTAMS being filed. You just have to meet certain weight and density requirements.
Cost...For a large rocket, you would probably need a 3000 gm balloon (can lift about 25 lbs) and two tanks of Helium. Balloon cost: ~$350. Helium cost: ~$60/tank. (you could go hydrogen and half the gas cost) You may need a larger balloon for a "P" sized rocket, so the cost would go up. There are some groups making their own Zero-Pressure envelopes out of dry-cleaning bag like material.
Then you need tracking electronics on both the balloon payload and rocket, and ignition electronics on the balloon payload. Talk to your local HAM clubs about this. The ultimate foxhunt ;) Of course, recovery area is much larger than your typical rocket launch. When chasing balloons in North Dakota, we generally go at least 60 miles, and sometimes over 200 miles. It just depends on how long the balloon and its train stay in the Jet Stream, and how fast the Jet is that day. We've had payloads travelling over 120 mi/hr ground speed, needless to say, we couldn't keep up with that one, but we did recover it the same day we launched it.
We have some info on how to do a balloon launch (including some of the regulation info) on our North Dakota High Altitude Balloon Group site.
Jerry Irvine wrote in news: firstname.lastname@example.org:
Jerry, with respect, I really have to disagree with you. Clunky and difficult to do right, yes. Cheap? Reliable? Definitly no. I've got a
*lot* of experience in launching weather balloons and ballons carrying research equipment. To get a payload of more than a few ounces, you need a big balloon. You can go with the old latex "weather balloons" (or a "balloon train") but the condition of the surplus ones are "iffy" and new latex or poly balloons are very expensive. Next you need gas cylinders, regulators, hoses, and a way to carry them to the launch site. We had a van that was specificly designed to do this. Other research projects used either modified U-hauls (please don't tell them!), or trailers designed for the task. A big balloon takes a lot of gas so you'll need a lot of cylinders - you don't want to just throw them in the back of a pickup.
You know, we launched a lot of stuff right next to an airport and never filed a notam. Never had any complaints. One other thing to note - launching a big balloon is a bugger. We had a large tarp that had velcro along one edge. The tarp was folded over to form a long tube. The balloon was placed inside to inflate, then when everything was ready to go, someone would grab the strip pf velcro and take off running. This would "unzip" the velcro closure, allowing the tube to open up, freeing the balloon. I don't want to say this can't be done by amateurs. It certainly CAN. It will just take a lot of ingenuity, planning and money to get it done. Plus you have to be prepared to fail. But the success would be *really* cool!
I'm sure fin stabilization will work to a degree (although I don't have any hard figures for you). But fin stabilization won't be nearly as effective as closer to the ground. Consider that at 100,000 ft, ~90% of the atmosphere is below you. You can actually see this in some of the videos and stills our group took at this altitude. A thin band of lighter blue quickly fading to the black of space.
On that same line, with less atmosphere, there is less friction, so I would venture to guess that a rocket should go higher from the launching altitude than it would from the ground (again no hard numbers...)
But one other thing to consider, is that once you get above the Jet Stream, the atmosphere calms quite a bit. I've been on several chases where above ~75,000 ft, the balloon stops moving laterally (it would continue to rise). We have sat in our cars visually watching the balloon (which gets to about 60ft in diameter if using a totex 3000 gm) for 15-20 minutes while we watch the GPS location signal drift
Dan, does your group have a website? I'd love to see what types of projects you've worked on WRT scientific ballooning.
I would have to second the "iffy" nature of surplus balloons. Our group had picked up a few, and they were literally falling apart. I have no problems mentioning our favorite supplier: KayMont. We have tried both KayMont and KaySam, and have found that the KayMont balloons, while a little spendier, were much more durable. We tend to use the surplus ones as demo tools for any of the talks we give.
We've had our share of vehicle "mishaps". Thankfully, mine wasn't one of them. Although an engineering group we were working with tried to drive a State Fleet pickup through a wet field once...needless to say they weren't too successful.
Also, you don't necessairly NEED a regulator. We tend to use one (went from an old party balloon regulator which took 30 minutes to fill a 3000 gm to a professional HP regulator that can really let the gas through, inflation in about 10 minutes), but when I was at the Great Plains Super Launch 2003, there were several groups that didn't have either a regulator or a shut-off valve. We really didn't want to be near their filling pickup (yes they used a pickup to transport their four cylinders of helium).
How heavy was the stuff you were launching? Technically if over 12 lbs, you need a notam. You can string some lighter packages together, but at a certain point, the FAA regs do require a notam. We tend to always file one, even if our payload fits under the exempted category (we never know until we actually get out to the field). We have always had a good relationship with our ATC people, and wanted to keep it that way. Plus it gives something for the pilots to fly over and take an interest in (precisely what a notam is suppossed to prevent...)
Our group is completely amateurs, and was started by someone who wanted to give it a try, and totally funded out of pocket until recent years. Out of all of our flights so far, we have only lost one (knock on wood), our first. That one didn't even have a GPS APRS transmitter on, stricly DFing for tracking and recovery. We have become spoiled by GPS of late...Maybe we need to take the rockoon challenge more seriously, and actually do a HPR one someday...
I launched a high alt balloon a few months ago, and it was a 1500g Kaymont (with a 6lb payload), which was 64$, including shipping.
Well, perhaps I did it the novice way, but I had a standard K size tank and a single hose. You have to be careful about the valve, but I had the thing filled in about 5 minutes. The K-tank of helium was about 73$ total. Next time, I plan on using hydrogen which can run as low as 24$ a tank rental (and you get more lift).
Well, you're SUPPOSED to file a NOTAM, not that it really helps. I mean, it's big and slow and can be seen from over 1 mile away, so it's really not a problem for pilots unless they're in IFR conditions (and you're not supposed to launch a balloon in those conditions anyway). On a side note, if the balloon is over 6 lbs, exceeds a certain density/side area, or weighs more than 12lbs (with 2 attached payloads), you're "supposed" to have 2 independant cutdown mechanisms in case it flies into a unwanted airspace.
My total was just under 1000$. Then again, I was really pushing "cheap".
Wow, that's where I need to be launching my next one. Even at 90k ft, some of my pictures were slightly angled, indicating the payload was swinging to some extent. Then again, I'm in the southeast US where the weather might be more turbulent.
Eventually, but not until the rocket achieves a much higher speed than it would need at sea level. At 100kft, the air density is about 1% or
2% what it is at sea level.
Depends on the engine, but with a really light rocket at 100kft, a J or K engine, and a nearly vertical launch, you 'could' hit the official boundary of space (100km).
The real problem is launching it vertically. From the time you ignite the motor to the time you have sufficent fin stabilization, the rocket is free to tilt (as you don't have a launch rail...and if you did, it would need to be anchored to a heavier mass to make sure the launch rod didn't rotate with the rocket). Additionally, you may have some swaying present from the balloon, plus the very small chance the rocket will hit the balloon.
I've thought about spinning it up prior to ignition, but that opens up some new design problems. My jury's still out.
Some of ours are also slightly angled, but you should really see our video footage. The first video we took was initially watched on a big screen TV, and almost made people motion sick from all of the spinning and swaying. Our next video caught the violence of cut down (we were wondering why our components came back all bashed up, and finally found out why ;) A parachute doesn't work very well at ~100,000 ft (not enough air to inflate it)...
The best thing about North Dakota and Eastern Minnesota: The recovery. We have gravel roads every mile in a NS/EW pattern, so unless you land in a lake, the most you usually have to walk is about
1/4-1/2 mile, sometimes less with minimum maintenance roads between section lines.
Here's a nice horizontal image from ~80k ft:
All the photos from that flight (taken at 2 minute intervals):
And our mission report:
We didn't run GPS/APRS on that mission, so our altitude was estimated via photographic measurements at ~86,000 ft (we got some good downward shots of the 1 mi x 1 mi section lines, and used some software to figure out the height) and compared to the rise rate estimate. This was only our 4th flight (I wasn't really involved at that time) and it took place in July of 1999. It was also the first flight test of a horizontal camera by our group, so beginner's luck ;)
If you have some time, go ahead and read through some of our mission reports:
make for interesting reading if nothing else ;)
P.S. If you want more info about the UND group, you can contact me at: mgerszew at volcano dot space dot edu I can put you in contact with our group leader in Grand Forks (sadly, I'm not there anymore, but may be again in the future) and answer any other questions you have.