Position Statement for the Ultralight Airship

The previous position statement no longer reflected the "consensus" of the group. It was planned as a 2 person aircraft. This no longer the majority position, as has been shown in surveys. So this an attempt at codifying a new document of agreement.

We agree that the prototype airship built by the SmallBlimps forum should:

• qualify as an ultralight aircraft under FAR part 103 regulations.
• demonstrate the ability to take-off and land without the assistance of ground crew.
• cost less than $20,000 (production model should cost less than $10,000)
• be trailer-able from a storage location to a flight location by common vehicles.
• be deployable from and retrievable into the trailer by one person in less than 1 hour.
• be able to take off and land from open fields, clearing a 50 ft obstacle, in less than 500 ft.

Please post "signed" below if you agree with this statement.
You post "unsigned" at any time to remove your approval of this document.
Please also post any suggested modifications. 

Jake Hill,
Signed

I still believe there needs to be an LTA option. There is a great simplification in an LTA, control and stability wise. LTA is a natural stepping stone to an HLA solution. AN LTA has a lot of forces and moments to be resolved. An HTA adds to this so now you have to design an airship and an airplane all in one.

So let's design one flight mode now and build toward the other as a method of project simplification.

I don't agree. I believe being heavy can simplify airship flight. If it loses power it can glide down. It would function just like and airplane with increased roll and pitch stability.

Take an ultralight trike and replace the wing with an envelope. It would fly more like a trike than an LTA craft.

I agree with the April 2010 SmallBlimps Position Statement. It is a good summary.

Signed,
Allen Meece

I'll try to make my UL design capable of both LTA and HTA flight modes. It might be easy.

I'll just try making an HTA that has extra room in the envelope for the addition of more lift bags for drifting the skies in LTA mode with the engines off for some peace and quiet. mmmm, that's the best type of flying.

Vent some of the cheep! H2 lift gas to go HTA to land without ground crew assistance.

sure, a hybrid HTA/LTA will need a frame and envelope bigger than the smaller, faster HTA-only ship but maybe it will still  fit in the UL weight budget. We'll see. and I ain't afraid of slow.

I do know the extra flight duration that an LTA offers will be a wonderful feature.

I can go along with this statement with some modest reservations. Once the pilot is aboard and the ship is set to the desired weight (all airships fly a little heavy, with disposable ballast) he should be able to launch and land unassisted. Exiting the craft is another story.
Since this craft is going to be a hobby type thing, like hang gliding or ultralight flying, friends and supporting people are going to be around. It's just natural to share this kind of thing, and family is going to want to be around in case the intrepid flyer does need some kind of help.
Back to exiting. It's standard procedure for someone to toss ballast onboard an airship so the pilot can exit without the ship leaping for the sky. When the pilot boards, the ballast is removed, and the ship is trimmed for flight. This is going to require help, not so easy for the pilot to do this.
For water landings, water can be pumped and dumped to accomplish this, but we're not there yet.

Signed, Mike Kirschbaum

What if the pilot were tethered to the airship? Then he could walk around and anchor the tether while the airship floats above him. Then the airship would not have to be heavy when empty. 

The position statement does not say how the airship needs to operate without a ground crew, just that it should be able to.

What if you fly down to an empty field to go to the bathroom? Will you be able to stay on the ground?

If you are tethered to the airship then you could pee while if floats above you. Then you pull it down to ground level and climb back in before take-off.

This would work if the airship's buoyancy supports its own weight plus a fraction of the pilot's weight. 

Why just not stay afloat, maybe above some woods....

Poor campers......

They are covered if they are in their poop-up campers.... oooohhhhhhh

I did a cursory spreadsheet for a bare bones airship in a different discussion. ( ultralite design pitch) I'm still concerned that the 254 limit may be too stringent for a first ship.

I haven't seen numbers from anybody else that show plausibility.

I felt the UL Marvin airframe could be simplified a bit so I'm re-designing the UL to have even fewer spars. Now making another "stick and string" model of the airframe. Should be able to do a decent weight budget in a week or so.~~~~ I'm trying hard to design an interior cabin for better windage but it'll need valuable space inside the envelope, requiring a bigger envelope.~~~~~ With a one hp gen and two ten-pound motors, the propulsion system is only about 50 pounds. My Omega Spar frame weight is about 20 pounds. That leaves roughly 180 pounds for shrink wrap envelope and PE lift bags.~~~~~~~~ 254 pound UL looks doable from here. NAV

One of the other calculations is a load budget. What loads are applies to the craft where? This gets into a study on "Strengths of Materials". For the non-structures person- there are two approaches.

1. Look up the various structural situations in Roark's Handbook.

2. Get a Finite Element Analysis program and model and mesh it.

O.K. maybe three,

3. Get an aero-structures type from Lockheed-Martin or Boeing on the team and tell them you'll give them free rides if they do some free work for you.

During one of my tours with Lockheed-Martin, I took their internal aero-structures course. It's not for the faint hearted.

I have some numbers here which show the feasibility of the UL concept. 

So your craft is going to be a blimp with a under hanging gondola?

Yes, as a hang glider or UL trike slings the pilot under the wing. 

Good Statement.

The next step is the calculation of the center of buoyancy. This tells you where to put the center of gravity.

Let me do a digression. Let's say I have a ship. It is a ultralite. It weighs 254 lbs and I weigh 200 lbs.

The center of buoyancy(CB) is 10 feet from the nose. The center of gravity(CG) is 12 feet from the nose because I thought this arrangement of parts and stuff looked cool.This also involves weight distributions due to the shape of the ship! The ship now has a nose up moment of 908 ft-lbs. IF I'm HLA, my controls will have to generate a correcting 908 ft-lb. moment to get me level. You see because of gravity, the CG will drop to line up with the CB.

This is why you calculate the CB and then arrange parts and pilot location to put the CG below the CB. Otherwise gravity will become your worst enemy.

In our next episode, we'll examine why the Center of Pressure can kick out butts even after we have a perfectly balanced ship.

Until then, sweet math dreams...

I want to add that, the prototype will probably cost more than 10,000 dollars even if a production model costs less. I am going to edit the position statement to reflect this.