Use of Balloon Assisted Launch System

Hi
I think this is the correct section of the forum, but feel free to move it
I have launched both small model rockets and high altitude weather balloons and I have researched combining the two It is definitely possible however there does not seem to be any consistent information regarding the effect that it will have on the rocket. Many sources state that the different is marginal, however even though they are talking about model rockets they seem to get caught up in reduction of orbit speed. obviously with a model rocket I would not be looking for reductions in the amount of orbit speed but reductions in amount of drag and therefore an increase in altitude. I found what I can only presume to be a reputable source on the subject - NASA's Proposal for a Balloon Assisted Launch System. It also was based on reaching LEO but it stated that: "A simple calculation using MATLAB that compared a launch from 120,000 ft with a ground launch suggested that a 25% decrease in required propellant mass was possible with a high-altitude launch system."

As this was for LEO orbit where the drag would of been reduced, but the delta v would of barely been reduced, meaning that for a straight up launch rathe than a launch aiming to orbit, surely there will be a larger decrease in the amount of propellant required. Would it be fair to assume that for a standard straight up launch, you would see a decrease of at least 35% in the propellant required as the atmosphere is 99% thinner? Therefore would the rocket theoretically have an altitude increase of roughly 35%? Obviously there would be no cost saving of this type of method and I would only be doing it for the challenge of it

To conclude, would a 35% altitude increase be a fair assumption?

Oh boy.......this is gonna be good....

ikr

This has been talked about many times on this forum and about 4 years ago on the Rocketry Planet Forum. Some people claimed they that had it all figured out and since then simply have faded away.

ali8bongo said:

Hi
I think this is the correct section of the forum, but feel free to move it
I have launched both small model rockets and high altitude weather balloons and I have researched combining the two It is definitely possible however there does not seem to be any consistent information regarding the effect that it will have on the rocket. Many sources state that the different is marginal, however even though they are talking about model rockets they seem to get caught up in reduction of orbit speed. obviously with a model rocket I would not be looking for reductions in the amount of orbit speed but reductions in amount of drag and therefore an increase in altitude. I found what I can only presume to be a reputable source on the subject - NASA's Proposal for a Balloon Assisted Launch System. It also was based on reaching LEO but it stated that: "A simple calculation using MATLAB that compared a launch from 120,000 ft with a ground launch suggested that a 25% decrease in required propellant mass was possible with a high-altitude launch system."

As this was for LEO orbit where the drag would of been reduced, but the delta v would of barely been reduced, meaning that for a straight up launch rathe than a launch aiming to orbit, surely there will be a larger decrease in the amount of propellant required. Would it be fair to assume that for a standard straight up launch, you would see a decrease of at least 35% in the propellant required as the atmosphere is 99% thinner? Therefore would the rocket theoretically have an altitude increase of roughly 35%? Obviously there would be no cost saving of this type of method and I would only be doing it for the challenge of it

To conclude, would a 35% altitude increase be a fair assumption?

Click to expand...

Way off, 120k launch altitude will increase altitude by a factor of nearly 10. A sea level G80 rocket goes, let's say, 3,000 feet. Altitude projections said that over 30,000 feet on the same G80 when launched at 120K feet.

So for a suborbital flight at around 120,000K altitude is estimated to increase by a factor of ten, do you have a link to the projections? Also does anybody know of any other projections that are realistic? The "how" is going to be all part of the fun

op:

@TopRamen: Do you mind if I join you? op:

I'm not sure whether you'll find the information you seek regarding the aerodynamic effect on the rocket, but folks have been dabbling with "Rockoon" flights for quite a long time. Search the Web with that term (if you haven't already), and you'll find several projects, including one by Bob Brown, a near-space/amateur radio balloon expert, and various other research and academic endeavors. Forgive me if you're already familiar with these.

Mark

OK, still new here kinda, but I never turned down free popcorn. Someone mind explaining WHY it is being busted out though? Don't need the ELI5 version, just a summary.

Tanarin said:

OK, still new here kinda, but I never turned down free popcorn. Someone mind explaining WHY it is being busted out though? Don't need the ELI5 version, just a summary.

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As wonderful as ingenuity is.... There have been numerous threads I've seen on here detailing why this is not possible, especially at a hobby level. I think some of them ended poorly...

Nate

ali8bongo said:

So for a suborbital flight at around 120,000K altitude is estimated to increase by a factor of ten, do you have a link to the projections? Also does anybody know of any other projections that are realistic? The "how" is going to be all part of the fun

Click to expand...

You can duplicate with any altitude prediction program. I used WRASP. It's close enough.

dave carver said:

You can duplicate with any altitude prediction program. I used WRASP. It's close enough.

Click to expand...

Open Rocket lets you set temperature and pressure. Altitude/pressure is not a linear relationship, but there are lots of tables o this interpipes deal.

op:

Getting up there doesn't take much delta v, at least when you compare it to getting into orbit. I like to tell people that getting to space is hard, but getting to orbit is ten times harder. (Okay, not true by delta v, but certainly complexity.) If your goal is to get something to float around in space for a couple minutes, you take out 120k ft of gravity and drag to overcome, which is certainly significant when space is only another 200k more from where you are (and bye-bye drag). If your goal is to get to orbit, it still takes away a fair amount of propellant, but now we're talking a fairly sizable and stable balloon.

nute said:

As wonderful as ingenuity is.... There have been numerous threads I've seen on here detailing why this is not possible, especially at a hobby level. I think some of them ended poorly...

Nate

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Oh, it's entirely possible. I calculated a $30,000 cost to use Dr. Rocket modular components and build a "simple" 2 stage N2000 to N2000 rocket to hit the first level of the CATS Prize then use the $50,000 from that to do a 2 stage with 2 strap on N2000. A great deal of the money was for 9 polyethylene bags and helium to fill, approx. 15 bottles for the first level and 20 for the second rocket. Launch legalities easy to bypass, we intended to use an abandoned offshore oil drilling platform in Mexican waters.

One thing I thought about was not using helium but filling the bags with hydrogen. Can you imagine the flare when the rocket would have blasted it's way through the bags, igniting the hydrogen on it's way past. Biggest single worry was filling the bags, any wind comes up and it's over, the polyethylene bags are made from the same plastic they make dry-cleaning bags from.

It all fell through when the 2 radio jocks who were to help raise the money were very suddenly out of work when their AORock station sold to Clear Communications and they went Top 40 Back in my "plan big" days

I have researched the term rockoons and read a lot of technical papers which highlight the main two problems as being rocket orientation and maintaining the rockets flight path as fins are essentially pointless and a launch tower would have to be 72 times bigger than on earth. I have found several reputable sources that also state that a nine or ten fold increase in apogee is realistic and I have found out about a project called the "far horizons project" which claims that they can hit an apogee of 120KM using a 1.7Kg rocket. I have contacted the project and they states that the 120KM is achievable using a rocket of that size. The rocket was two stage and uses a J228 111ns motor for the first stage and a h125 320ns motor for the second stage.

After learning about the obviously huge advantages I decided to research the best ways to overcome the two hurdles; there are obviously many proposed method with some being more realistic than others. To solve the orientation problem I am thinking of using a stabilised gimbal, obviously I will ground test this method to determine its feasibility. I am then planning on using a rotating plate to give the rocket the required spin in an attempt to ensure that it follows the intended trajectory.

I would be interested in reading the threads highlighting the problems if anybody has a link to them. Also am I missing any other major problems? I think this is the perfect project to combine my love for HAB ,amateur rocketry and difficult projects

Motor ignition is also much more challenging at that altitude. There's little air to conduct heat from the igniter to the propellant. And ensuring that batteries and electronics work is difficult.

-- Roger

When it comes to motor ignition there are a couple of ways to solve the problem, the simplest being containing the ignition powder in a contain which is pressurised to sea level which has a diaphragm which can break and subsequently light the fuel. I think that I will be able to handle the electronics side of things as it is not much more complicated than I have experienced with my previous balloon flights. I can't help but feel like I am missing some major problem which is why nobody really attempts it :/

Have you seen the Lohan project at Theregister.co.uk?

ali8bongo said:

When it comes to motor ignition there are a couple of ways to solve the problem, the simplest being containing the ignition powder in a contain which is pressurised to sea level which has a diaphragm which can break and subsequently light the fuel. I think that I will be able to handle the electronics side of things as it is not much more complicated than I have experienced with my previous balloon flights. I can't help but feel like I am missing some major problem which is why nobody really attempts it :/

Click to expand...

In a word: money. You'd better have a lot more than you think it's going to take. I think just getting a single stage motor to light at 100k feet would be an accomplishment. That would prove you can do it, making further, larger flights as you acquire ground support gear.

Another problem is red tape. You have 2 Gov agency's to make happy, FAA and the AST, the Administer for Space Transportation. FAA has a ceiling where the AST takes over. Both are fairly easy to navigate if you show you know what you're doing. It's 1 thing to balloon launch a data gathering package and a whole different thing to attempt to launch a rocket from a balloon. I'm not even sure to what level it's been done if at all.

This is what a 1 kg rocket launched in a zero drag environment could do for apogee if all went well.

This spans a propellant fraction from about 8% to 48% which shows an apogee improvement between 60% to 2665%. If you could launch a rocket from 30 km MSL altitude, you could in principle reach an apogee of 123 km MSL. The problem is that you would be able to get near that altitude gain without a large stable balloon borne launch platform and a vertical stabilization system in the rocket.

At 30 km altitude, there is little air, so aerodynamic stabilization by fins does not work well. If your rocket needs 50 km/hr to attain aerodynamic stability at sea level, you need to reach 500 km/hr at 30 km to achieve aerodynamic stability, and you can't have a launch rail long enough to attain that rail velocity. Your rails at a minimum must be stable and pointed vertical thru launch so it is going to have to weigh at least 10 kg and probably a lot more to be stable.

A 1 kg rocket with 48% propellant fraction has no room for electronics. You would have to increase the weight of the rocket if you want a transmitter and a vertical stabilization system. The weight multiplier must pass thru the entire system, so you are realistically looking a looking a 50+ kg balloon package.

A balloon payload of this weight will require British and most likely European ATC permits and air space waivers and clearances. These will be difficult if not impossible to secure as you would have to prohibit air traffic in a 100 km radius of the launch zone, and the cost of such an effort will be prohibitive.

Even if you could do everything to secure permission, you would most likely find it less expensive to build a much larger rocket and ground launch it.

If it were easy, and doable, it would have already been done by an amateur group, but it hasn't been. During the 60's the US government conducted several dozen rocketoon launches and determined it was easier and less expensive to ground launch and no further serious attempts have be mounted.

Bob

dave carver said:

In a word: money. You'd better have a lot more than you think it's going to take. I think just getting a single stage motor to light at 100k feet would be an accomplishment.

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Why not use a hypergolic ignitor?

What is a hypergolic ignitor?

Thanks for the detailed info Bob, what program did you use for those calculations as I don't know what the best software will be to run my calculations that will be able to handle high altitudes (I am on a mac).

ali8bongo said:

What is a hypergolic ignitor?

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There are chemical reactions known as hypergolic reactions, whereby simply combining two chemicals results in ignition. Because failure to ignite was not an option on the Apollo lunar lander, the lander's ascent engine used hypergolic fuel.

Why isn't it normally used then, is it more expensive/complicated than traditional methods?

ali8bongo said:

Why isn't it normally used then, is it more expensive/complicated than traditional methods?

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Expensive materials and handling precautions, toxic, corrosive, explosive, lots of good reasons for the amateur to look at some other method. The components include chemicals with catchy names like, White Fuming Nitric Acid, UDMH, Hydrazine, High Test Peroxide, T-Stoff, C-Stoff ( T and C used in Me-163 Comet rocket fighter) etc, all have one thing in common: at the very least all are dangerous.

rharshberger said:

Expensive materials and handling precautions, toxic, corrosive, explosive, lots of good reasons for the amateur to look at some other method. The components include chemicals with catchy names like, White Fuming Nitric Acid, UDMH, Hydrazine, High Test Peroxide, T-Stoff, C-Stoff ( T and C used in Me-163 Comet rocket fighter) etc, all have one thing in common: at the very least all are dangerous.

Click to expand...

I recall one or more Apollo crews having a few misgivings about living atop such a brew for the few days they were gamboling about on the Lunar surface.

While hypergolic fuels are certainly all of the above, I was suggesting a hypergolic ignitor, not a hypergolic motor. The small amounts necessary to perform an igniting function shouldn't be too big of a deal.

simonov said:

Why not use a hypergolic ignitor?

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Why not? Because he's using a solid rocket motor, not a liquid rocket motor.

Bob