Lifting Body?

How would you guys define a "Lifting Body" as it pertains to model rocketry. You know like the X-24 of HL-20.

-John

Hi John,

Have a look here .

JNUK, that is "Dead Sexy". If any members of my club do something like that I will pass out!

However, it does not actually give a definition of "Lifting Body" per se. I know it's one of those "Ya know it if ya see it," kind of things, but how would we define it for say a NAR competition?

-John

Well, as I understand the distinction, a lifting body is an aircraft that generates lift with it's entire fuselage, rather than just from wings. A lifting body may have short stubby wings or the entire fuselage may be the "wings" (not to be confused with flying wings).

The best example I can think of in model rocketry is the old Centuri X-24 Bug:

https://www.spacemodeling.org/JimZ/ka-12.htm

Squirrel Works sells a similar model (but it's not a clone):

https://www.squirrel-works.com/glider.html

I've flown the X-24 Bug - it actually glides rather well. A really fun model.

Dr. Zooch has a lifting body kit that rides piggy back on a booster stack...shuttle style. It's pretty cool.

https://www.rocketryforum.com/showthread.php?t=201&highlight=Zooch+lifting+body

No definition to offer, but here's a cool LB model I remember from
TRF 1.0

https://www.rocketryforumarchive.com/showthread.php?t=16608

Here ya go:

https://www.spacemodeling.org/JimZ/tir-24.htm

I think this is what you want.

Brianc -- COOOOOOOoooooOOOOooOoooolll! THAT looks like it could be fun. I have been trying to get some detail data on the old Lockheed Star Clipper, and this shares a family resemblance.

But mostly I have stuck with the Centuri X-24 and Quest HL-20.

Mach-7: I have read that TIR a couple of times. Good info, actually, and it DOES work just fine without fins. I just designed a little recovery pod for the motor to keep things a tiny bit more NAR friendly.

The stupid things actually do glide - a little, and are cool for glider guys with small fields.

I did some (just-for-fun) competition rules the other night after putting the kids to sleep.



View attachment Lifting Body 002.pdf

120 seconds? For a lifting body glide? Are you kidding? Some L/D considerations need to go into this work... that glide time is off by a power of 10. The best one of my lifting bodies ever presented about a 12 second glide.

These old NASA shapes were called "lifting bodies" only in comparison to capsules....which were themselves only marginally better than falling rocks. Capsules could be "steered" by trimming one side to ride low, giving an L/D on the order of 1:1 (literally); they could be "steered" by rotating the capsule to point the low side in a new direction.

Lifting bodies were a small improvement on this, in that some shapes had L/D ratios of up to 2:1 or 3:1, but they still fell pretty much straight down, for all practical purposes. These were not good aero shapes for cruising across the Atlantic. Some lifting bodies could be accelerated by diving them at the ground and then using pitch controls at the last second to flare for landing, but timing on this maneuver was rather critical, and airspeed was rapidly decaying after the flare (or even, during the flare) to where the pilot would only have seconds to match up a successful combination of flare, descent rate, speed, altitude, and alignment with the runway. In technical talk, landing a lifting body this way was "hairy."

There was a reason that the preferred approach was to use a parachute.

Yes... I know.

I've been studying lifting bodies since 1973. I developed my current shape when I was in high school in 1975 and flew the working version is 1977.

Several years ago, a friend of mine (one of my college roommates) who works at DFRC took one of my lifting bodies in and showed it to Dale Reed (the father of lifting bodies). Mr. Reed studied it closely and said that it was a terrific and unique (lifting body) shape and looked as if it would be "a great hypersonic shape." After Mr. Reed's death I was fortunate enough to receive some of his hand-written notes as well as the unfinished airframe of one of his R/C airplanes.

Anyone reading this thread who really wants to learn more about lifting bodies should get a copy of Dale Reed's book "Wingless Flight" (mine is autographed nuyk nuyk ) AND get a copy of "Flying Without Wings" by Milt Thompson (the test pilot who flew more lifting body flights than anyone else) and Curtis Peebles (Milt's ghost writer). These books will tell the readers more about lifting bodies than anyone here can. Another good source is the book "From Runway to Orbit" by Kenneth Iliff (who was early into the project with Reed) and Curtis Peebles.

BTW- just for referance, the subsonic L/Ds for the lifting bodies was never 2/1. In fact the M2-F1 was caculated as being 5/1 and the heavy weights were never lower than 4/1 with the unsat minimum being considered as 3/1 (ref. the above listed texts).

Dr.Zooch said:

BTW- just for referance, the subsonic L/Ds for the lifting bodies was never 2/1. In fact the M2-F1 was caculated as being 5/1 and the heavy weights were never lower than 4/1 with the unsat minimum being considered as 3/1 (ref. the above listed texts).

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While it is true that the experimental vehicles sometimes attained higher L/D ratios, most of the designs we studied for operational needs did not do as well. When you trade off planform area (including "wing" area?) to reduce weight, to improve launch margins and on-orbit mission performance, you don't always end up with the luxury of high L/D.

Those experimental lifting bodies weren't lugging around X-thousand pounds of cameras or electronics.

Yeah- agreed. I guess I wrote that post pretty late in my day, it came off like I was lecturing or something... did not mean that.

The only advice I meant to offer was to direct folks to go and read the books.

There is also the transition factors (hypersonic to super sonic to subsonic) that need to be applied. As I recall, the SV-5 shape had some amazing projected hypersonic L/D. I've never dug deep enough into the archives to find out what the actual flight subsonic L/D average was for each shape- but it would be fun to know. If you have a handle on that one powderburner feel free to share it. It'd be some fun lifting body trivia to dedicate a brain cell or two to.

Its fair to say that you and I both have a soft spot for lifting bodies. If you don't have one of my LB kits yet- PM me.

Dr.Zooch said:

As I recall, the SV-5 shape had some amazing projected hypersonic L/D.

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And right there you have the main reason for using a lifting body shape.

Anything like a wing meant extra structural weight that was a penalty on the way up and while on orbit (extra weight = extra propellant for the same delta-V). About the only time that the lifting-body-technology was useful was for unplanned re-entry points while on an orbit that did not line up with "home." The ability to maneuver cross-range (to some extent) added the necessary amount of control and safety to successfully return to base. Toss in some LV constraints on lifting capacity and you quickly have to get pretty ruthless with selecting vehicle features.

As I recall, the trade studies we did all indicated immediately that any structure that was purely "wing" should not be on the vehicle. We were left with getting whatever L/D we could by body shaping (which wasn't much). The trades between gliding all the way to touchdown (with high sink rates, heavy landing gear, beefup for airframe load introduction, etc) and popping a parachute at 5000 ft pointed pretty clearly to the parachute.

I've read a couple of those books you recommended, and they were very good. Now I'll have to hunt down copies of the rest...

powderburner said:

And right there you have the main reason for using a lifting body shape....

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Excellent summary! All of the posts in this thread have been very educational, but for someone like me who has no grasp of the math and who has minuscule (if that) knowledge of aerodynamics, you and the good Doctor are explaining it in a way that is quite accessible. (I can actually follow along!) Thanks!

I was originally a bit taken back by the para-wing concept that went with the X-38 (probably because it eliminates the meat-based control actuators similar to myself). But after I saw the test I said to myself that it was terrific concept for a lifeboat. It should NEVER have been canceled- it would have worked very well IMO.

To a lot of you who may be reading and are like MarkII (never been exposed to advanced aeronautics- *so engineers please allow some slack as I use some non-tech terms to explain*) I wanna talk a bit about those “steep” approaches that lifting bodies make. Recently, while working at my bench, I had some DVDs of early shuttle flights playing in the background. The meatpuppets in the TV media mentioned a zillion times how steep these approaches were and how the pilots would “…get only one chance…” to make the runway. They really drama’d that point up as much as they could, and do the same today to a certain extent. The fact is that, what the early lifting body pilots called, “dive bomber” approaches were (for the most part) developed with the M2-F1 as an energy management tool.

These sorts of approaches have some very real advantages over the ones that I might do in an airliner or corporate jet. First off, they allow a very low L/D shape (such as a lifting body or the shuttle) to use gravity to effectively store inertia in a sort of energy bank. This inertia can then be spent in the landing flair allowing a shape that has the aerodynamic characteristics of a pair of pliers to land on a runway. It eliminates the need for air-breathing engines and the fuel to run them. Additionally, the dive bomber approach does not lend itself to being influenced easily by local weather turbulence. Thus, the pilots are not wasting time, effort and energy correcting for turbulence on the approach. Another advantage is that these approaches are extremely accurate to fly. You look at the point on the runway where you want to go and you’re goin’ there- period.

So, the fact that you only get one try at the landing and there is no go-around does not matter, because you do not NEED a second chance. In these approaches, when you’re on energy and lookin’ at the end of the runway, that’s where you’re goin’. Now… that said, to someone outside of these things that may sound scary, but to a professional pilot, it is simply a matter of numbers, focus and doing everything they way you are supposed to- in other words the sort of stuff that people like me have been doing all of our adult lives when we go to work. Piece of cake… as a professional pilot, once you’re off the ground, everything is just numbers. You’re trained not to think of altitude as being a height, rather it is always a number that you manipulate. Same thing with airspeed and descent rate or ascent rate or heading and direction, attitude and bank- it is all a game of numbers. You need (this) to get you (that). You train with those numbers for that given situation to get that desired result, over and over and over and it always works. In the event that something goes wrong, you have a different set of numbers to switch to meet that situation. Sure it takes intense focus, but that is what ya’ do… focus. Granted, the people who flew the lifting bodies and those who fly the shuttle are VERY exceptional pilots- but the very basics are still the same.

That said… I’d give my eyeteeth to get my hands on that HL-20.

Dr.Zooch said:

That said… I’d give my eyeteeth to get my hands on that HL-20.

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It's not that difficult. For $8.39 plus shipping you can have your very own.

HL-20

Har har... verrrrry funny

I'm talkin' the NASA one, of course.

Foose- I'd better see you at Red Glare- you've been off the radar WAY too long.

Dr.Zooch said:

120 seconds? For a lifting body glide? Are you kidding? Some L/D considerations need to go into this work... that glide time is off by a power of 10. The best one of my lifting bodies ever presented about a 12 second glide.

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That is 120 seconds for MULTI-Round maximum (ten is "multi :confused2. I figured I would set the max outta sight, then tweek it back after some more "research".

Having tinkered with HL-20 (Quest) and X-24 (Centuri) I have found that they basically have a glide ratio of 1:1. A few have done better (finless variants), but not by a lot. I can't say as I have done much research into the trans-, super-, or hyper-sonic L/D of these types, since they are decidedly sub-sonic. I also prefer the conical shapes because they are very easy to build, are a tiny little bit closer to the ideal SSTO. Also I prefer Rocket Gliders to Boost Gliders, since a Boost Glider is really a chuck glider one throws with a rocket (with its own recovery device) rather than a rocket that glides back to Earth.

The contest idea is for clubs with small fields to do a Glider event. It has since been revised to be a multi-heat drag race event with the last glider to land moving on to the next heat (without the Multi-round max).

View attachment Lifting Body 003.pdf

I love it!

Ironnerd88 said:

JNUK, that is "Dead Sexy". If any members of my club do something like that I will pass out!

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I am currently working on a lifting body version of Ms. Frizzle's Magic School Bus. ;-)