There’s an old engineer’s joke when something gets dropped. They say “gravity check, still on.” Now I’m not going to distinguish between whether that’s an old joke or a joke for old engineers, but either way, aviation is all about mastering gravity.
Post WW2 the US Air Force was felt it had a good grip on mastering gravity, the key to their mastery however, was runway take-off, and the possibility that an enemy might destroy their runways was a major concern.
During the cold war, the US, for example, kept an defensive force of aircraft in the air continuously, by having the next one take off before the previous one had landed. This was a sledgehammer approach to minimizing the problem (and makes you wonder where the aircraft would have landed if the runways were destroyed).
Another approach was aircraft that didn’t use runways.
In 1947, Ryan Aeronautical produced the the Navy FR-1 Fireball, which had a thrust-to-weight ratio greater than 1. This bring up two things:
- Why anyone would want to name an experimental aircraft “Fireball” is beyond me, but it was the 50s and everyone thought we’d be flying around in space-cars by now, so I’ll give them some slack on their dubious name choices.
- A thrust-to-weight ratio probably sounds like the opening of a another “old” engineers joke, but it means the aircraft’s engine produced more force (thrust) than the aircraft weighed, hence it could accelerate vertically.
In 1953, Ryan were contract by the Air Force to create the X-13 Vertijet (shown below).
This was a small aircraft with a mere 21ft wingspan. Keeping the weight down reduced the power needs to lift and control the vehicle. The whole aircraft was hung by a hook onto the landing platform. The pilot entered the aircraft while the landing platform was horizontal and then the whole assembly rotated to the vertical. Jet engines (esp in the 50s) were remarkably slow to spool up and change thrust, so any engine hiccup was going to put paid to the pilot’s weekend plans. Notwithstanding, Pete Girard, and Lou Everett (both Ryan pilots) flew the aircraft from the vertical position. Pictures speak louder than words, so here’s a video of one of those events.
As graceful as this aircraft launch seems I bet the pilot was working hard to keep the aircraft stable. Certainly the Harrier has that reputation.
The Air Force lost interest Vertijet. Scaling it up to carry a useful weapons load would have been a challenge. The Air Force was still concerned about the runway issue, so they experimented with what was termed Zero Length Launch ideas (and, for inexplicable reasons, the Air Force came up with the acronym ZEL out of those three words). The ZEL idea was to rocket assist the take off of a fighter. JATO bottle rockets had been used to assist transport aircraft take-offs at the end of WW2, so it seemed a logical progression. The Zero in ZEL meant they were going to launch a normal fighter from … a trailer.
The first attempts were with a modified F-84. This seems like a strange choice since the slow accelerating F-84 liked the entire length of a runway (two if they were available) to take off. However, the addition of a tens of thousands of pounds of solid fuel thrust helped enormously.
The rocket assisted take off was a fairly reasonable idea. What was far less reasonable was the Air Force’s landing scheme. When the enemy denied them the use of their runways they’d use an inflatable rubber mat. Yep, you read that right, a giant inflatable rubber mat. It was 80ft wide and 800ft long with an arrester wire that the aircraft would snag in the same manner as landing on an aircraft carrier.
The first mat landing tore up the mat (surprise, surprise), wrote off the aircraft and put the pilot in hospital for months. The following, and last, landing was slightly more successful, but after two attempts the Air Force abandoned the mat. I suspect test pilots the world over breathed a sigh of relief.
Ignoring the mat, the ZEL take-offs had been a success and the Air Force moved on to using a more potent aircraft, the F-100.
The rocket motor was upped to 130,000 lb to cater for the increased weight of the F-100.
The launches were performed from a trailer and went well. In fact, Al Blackburn (the test pilot and writer of the book Aces Wild that I referred to in A Booming Controversy) reported the launch as “exhilarating” and better than anything at Disney. His second launch didn’t go so well as the rocket wouldn’t separate and he had to eject. Here’s a video of a launch from a hardened bunker.
Given the Cold War mentality, once the US was investigating an idea, the USSR had to investigate. In their case they were looking at the idea to be able to disperse their air assets and launch them as interceptors. One of the USSR’s pilots, Georgi Beregovoi, survived a number of launches in a modified MiG-19, and went on to to cosmonaut fame in 1965, but the Russians abandoned the idea in the same way as the US did. Distributing expensive aircraft (potentially nuclear armed) in fields all over the country was a recipe for disaster. For good reasons, Air Forces tend to pride themselves on being able to find all their aircraft, and especially their weapons.
Vertical take off is an idea that’s still with us. It’s been tried with all manner of aircraft to varying degrees of success, but the major obstacle is always there, gravity doesn’t quit.
And yes, I just checked.
Cheers
(Images courtesy of www.vectorsite.net and Wikipedia)
How many wrong ways to make a light bulb?
As always, Nigel, an interesting post, dotted with your own brand of wit.
Hi Sherry. Believe me, the are ways that seem even less sensible! What amazes me most if that got these ideas to work with comparatively small teams/effort.
Cheers!
“Gravity check”! Thanks for my morning laugh. But, gee, Nigel, why didn’t you tell the one about the weight to thrust ratio? 🙂
My favourite aeronautical joke is from the trenches of aircraft maintenance. The gag is for a seasoned maintenance engineer to ask a neophyte, “Hey, would you bring me a bucket of prop wash?”
VTOL aircraft worry me. Right about the time when they transfer from vertical to horizontal, it always seems to me that there must be a moment when there’s not enough vertical thrust to keep them aloft and not enough forward velocity to generate lift. It’s obviously not a problem, but it always gives me the willies anyway.
Hi Diane. Prop wash – very good. I saw a list of pilot squeaks sometime ago which had a whole litany of similar remarks. Have to see if I can find it.
When I did chemistry I can remember sending the new students down to the stores for a “long weight.” The stores-people we’re ever helpful in keeping that well worn joke going.
I sympathize with your VTOL worries. I think they do loose some altitude when converting. Me, I’d loose my lunch.
Cheers!
Hi Nigel. One of the interesting things is that most of these tests were done with aircraft that had been engineered and built for horizontal take off. It leads me to wonder about the shifting fuel weight and therefore shifting “center of gravity”. I wonder how many hours of slide ruling went on for all of there tests.
Based on my primitive and limited view of aviation It seems to me that even with an idealized zero lag time in the control systems the pilot would have been working with very little room for error.
In the age of computers the final obstacle to the Osprey program (assuming that money was no object) was getting the right software.
You’re right, the change in CofG is a factor at all times with rapidly maneuvering aircraft. The first tests done were with concrete filled dummy gliders, and they clearly showed the rocket position and attachment angle were highly important – the first couple of launches flipped over and ended up going backwards. Even in gently maneuvered civil aircraft burning the fuel in the right manner is a trick used to keep the CofG in the optimum position to give the aircraft the right angle of attack and minimize the fuel burn. Even fractions of a degree make a big difference over long distances.
The X-13 must have required an incredible touch. Jet engines are slow to wind up, the lag would have great and he had to do it all with his eyeballs and the seat of his pants. He had no Osprey computers to help him. It also didn’t cost 100M each!
Cheers
I LOVE these posts about the misadventures of aircraft. I’m easily impressed b/c my knowledge of aircraft doesn’t go far beyond knowing how to put my seat tray in a full and upright position.
Landing of a rubber mat was the killer. Really? Plop an umpty-ump (technical aeronautical jargon) pound aircraft of a hyped up version of a Yoga mat?
Do you have any LOO pix from these aircraft you can share with me? I’ll give you proper credit.
LOL, Gloria, if only you’d mentioned it earlier. I’ve just come back from vacation, I could have supplied pictures from loos around the world (or at least a bit of it). I’m highly impressed by your use of the word “loo,” I thought it was a British-ism.
I’m glad you like the misadventures of aircraft, I’m ok with the idea when its one I’m not in. My idea of an ideal flight is one characterized by words such as tedious, boring, and dull. And yes, whoever thought a rubber mat was going to lead to a comfortable landing was probably the same person who decided the size of a cattle class seat.
Cheers!