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Comment by blackguardx | Hacker News Reader

Technically, the space shuttle and this space plane are lifting bodies, which I think is pretty cool and elegant.

Capsules are lifting bodies too. Apollo had a L/D of 0.368 and "steered" by rotating. Dragon uses the same technique (albeit with a slightly lower L/D), and Dragon 2 will have a tungsten ballast sled so it can change its angle of attack dynamically during re-entry.

Even simple cylinders can be lifting bodies. Shuttle and Falcon 9 both have a L/D of 1.[1] On Falcon 9 the first stage acts as a lifting body, using the grid fins to "trim" the big cylindrical body making it act like a wing.

In the SpaceX landing videos you can see the stage pitch up on reentry. This is no accident. Upward lift = more atmosphere traveled through = more drag = less landing fuel needed = more payload to orbit. A nice optimization by the SpaceX team!

>you don't actually need wings by the way, it's kind of a common misconception around, you just need some lift over drag number, or lift vector - and steer back to the launch pad --- Elon Musk[2]

[1] https://spaceflightnow.com/2017/04/04/musk-previews-busy-yea...

[2] http://shitelonsays.com/transcript/npc-luncheon-with-elon-mu...

... there's something particularly evocative about this image taken during early lifting body research: https://www.nasa.gov/centers/dryden/multimedia/imagegallery/...

Thank you! I've never seen that photo, but it is obviously the inspiration for the Dynasoar poster: https://en.wikipedia.org/wiki/Boeing_X-20_Dyna-Soar

There isn't really a sharp distinction, is there? The primary method of generating lift for both wings and lifting bodies is simply the fact that it's an inclined plane moving through a fluid with positive angle of attack.

They each have some length of wing, but get a lot of lift from the shape of the fuselage. These craft wouldn't exist without lifting body research.

This space plane and the shuttle shouldn't be derided for gliding into landing. Not using fuel while landing saves precious cargo capacity. If the main argument against them is that they can't land on the moon, I don't understand why a future craft couldn't both glide into an atmosphere and use thrusters in a vacuum in to land.

> Not using fuel while landing saves precious cargo capacity

Those wings are also a lot of mass, and hence take away from payload. In fact, propulsive landing always takes less mass than wings in the limit of large craft size. (You can see this by taking an equivalent limit, the limit of thin atmosphere; for sufficiently thin atmosphere, the amount of surface area you need to brake diverges but the amount of fuel to stop propulsively is fixed.) In this sense, propulsive landings naturally succeed wings as crafts get larger.

I won't argue with that, but that isn't true in the case of the X-37, which is why it glides into landing.

Elegance in engineering is fulfilling the requirements in the simplest, cheapest way possible.

Following this principle I sometimes think the new east span of the Bay Bridge is/was a $6 billion boondoggle. The historical (and I thought, beautiful) original span was not retrofitted because Caltrans said they could build a new span for less that would have a longer lifespan. The simple, cost effective viaduct design was rejected as not grand enough for a Bay Area bridge and a short decorative, self-anchored suspension bridge was added to the viaduct for an extra $5 billion. It would sure have been nice if that money had been spent on a couple of additional bridges across the bay. One from the 101/380 to the 880 near the Oakland airport would sure help the traffic problems some. With interest rates near zero, I'm sure the finances for a toll bridge would work out. Just need the political will.

Yea, I'll withdraw "inelegant" from my original comment, since I was mostly intending to dispute (concurring with colordrops) the suggestion by Animats that wings are more advanced than capsules. ("It's time to get past capsules".) I wouldn't say the shuttle was a pillar of elegance, but I'm happy to agree that wings can be elegant on the right spacecraft (although, as I alluded to, the intuition that they are less wasteful than consuming fuel can be a bit misleading).

Thanks for your comments.

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