The FG successor to DARPA's Walrus

[spot]

Do people remember DARPA's Walrus? A defense project that was cancelled three years ago in the form of an airship the size of a football field which would take an entire equipped combat unit into theater. I think it was supposed to weigh in at 1,000 tons or something ridiculous. Full of helium for lift, but juggled so the beast wouldn't float off half-way through deploying its cargo.

Anyway, I woke up with numbers in my head this morning from dreaming up its successor. The FG Dirigible.

If you displace air with helium you get around 1kg lift for each cubic meter. That's because a cubic meter of air at sea level weighs about 1.3kg and a cubic meter of helium in the same place weighs about 0.2kg.

These things can't go high - every mile you go up, air in a given volume weighs about 0.87 times what it did a mile below. What they can do is travel over land as well as sea, they can get to anywhere on earth in less than 5 days at a steady 100 miles an hour and the bigger you make them, the more efficient they get. DARPA's problem with the Walrus is they didn't think big enough. We at FG know better than to make that mistake.

The FG Dirigible should have a ceiling of 2 miles and act as an aerial airbase for several squadrons of appropriate aircraft. I reckon we want three runways bedded into the heart of this thing with a runway length of 500 meters. If a naval aircraft carrier can get planes launched along a 200 meter ramp I reckon we can aim to be a lot more flexible. This means we can deploy several squadrons in places where currently we own no airfields. FG is weak on airfields so far.

That gives us the length. The dirigible needs to hold as large a volume as is consistent with good looks and aerodynamic feasibility. 500 meters long gives us, say, 300 meters wide and 250 meters high of which the upper 200 meters is lift-space for the helium and the bottom 50 meters is the 30 meter high hangar deck and five other 5 meter high levels, maybe four floors below the hangar to maximize bracing opportunities and one above for the same reason.

The runway lengths, the 30 meter landing deck height and the 100 mile an hour headwind means the FG Dirigible, unlike any naval aircraft carrier, can accept aircraft landings and take-offs up to the size of Boeing 747-400s coming in three abreast should the need arise, with 5 meter clearance below the wheels and another 5 meter clearance above the tails. It could easily accept Air Force One for refuelling, conferences and State visits. The half-kilometer runway length is adequate for either passenger plane model since they approach and depart at a speed relative to the airship of around 60 miles an hour, give or take a twitch, or even less if the dirigible can travel at more than cruising speed.

These dimensions give us the maximum gross loaded tonnage when deployed: 30,000 tons. 1kg lift per cubic meter, remember? 500 x 300 x 200 = 30 million cubic meters of lift space. Of which, to round things, we can have 15,000 tons dead-weight and 15,000 tons of cargo at sea level. That reduces to 5,000 tons of cargo at the 2 mile ceiling which is why we cap our height to that figure.

I think we should paint it light blue.

For structural calculations, given the plan cross-section we have 200kg hanging from every square meter of roof panel. I'm sure we can build geodesic bracing to prevent the internal runway and the five floors from flexing to excess. The runway itself can weigh 1,500 tons across 150,000 square meters or an average of 10kg per square meter for that entire level. The remaining floors can each weigh a fifth of that. That's 20% of the dead-weight, dividing walls and the outer skin can obviously form a major part of the bracing of the lower structure and add another 10%, the remaining 70% of the weight goes in bracing and infrastructure. Which leaves, I'll remind you, a 15,000 ton carrying capacity for the on-board squadrons, crew and whatever regiments are being transported to and from some as-yet unfought battleground which stands between FG and world domination.

I reckon you could land 100 main battle tanks and their accessories from one of these things. If we built ten FG Dirigibles we could turn mercenary.

When we put the proposal to the general public for funding, we have to emphasize the humanitarian possibilities of sending it to natural disaster areas. People like to hear that when you're describing warships.

[along-for-the-ride]

Nah...forget about the squadrons, regiments and calling it a "warship". Let's man it with a crew, medical staff, and a large team of trained volunteers. Inventory would be medicines, first aid equipment, food, toiletries, tents, clothes, etc. The destination would be anywhere that has just been visited by a natural disaster. The objective: To provide hope care,and comfort to the victims there.

[spot]

Any occasion when a device DARPA has a hand in happens to escape its natural battlefield environment and ends up instead as a boon to humanity is entirely incidental and probably puts its directors off their enchiladas.

FG, on the other hand, would be delighted to adopt your suggestion. You can be the first mate and take turns at the helm.

I really want it building just so I can see three formation-flying Jumbo jets touch down in it side by side. That reminds me, those half-kilometer runways have to have a high-grip surface.

[Scrat]

What about STEALTH???? You can't have something like that flying around with those other people seeing it. Tell you what, if FG is willing to toss in the plasma stealth option at a deep discount American taxpayers would be more than glad to pay for it. I personally would like it painted with a toothy shark grin also and a couple of eyes. Not light blue either, I think a dazzle camo scheme would be better.