To be clear, I said that X-37 does not scale _well_, especially in comparison to HL-20, not that X-37 does not scale, period. Specifically, I said that:

“It doesn’t scale well — the interior volume doesn’t go up fast enough to fit a sizable crew in before the vehicle exceeds launch constraints. HL-20 variant designs do better.”

To be more specific, X-37B launched on an Atlas V 501. That’s a 5-meter fairing variant of the Atlas V, the largest launch shroud around. Per this and other pix, the X-37B’s wings are already at the limits of that launch shroud:

http://en.wikipedia.org/wiki/File:Boeing_X-37B_inside_payload_fairing_before_launch.jpg

You’re not going to be able to launch a sizable crew on the X-37 without going to a much larger and unproven fairing (or bet on the come with a non-existent launch vehicle like Falcon Heavy).

And when folks talk about using an X-37-type vehicle in a manned role, it’s limited to crew down only, usually in an emergency role. Here’s one example, and it comes from an X-37 proponent:

http://www.spacenews.com/commentaries/100823-civilian-role-x37b.html

“No one has presented evidence that any lifting body can achieve an L/D at touchdown of greater than 4 or any runway landing, unpowered, at a realistic mass for a returning spacecraft.”

There’s a whole slew of tests that show otherwise, but even if this was true, there are ways around it. For example, very simple, small retrorockets could provide additional lift while the last couple hundred km/h are bled off during final approach and landing. That’s especially true in these days of precision vertical landers like Armadillo and Masten. It’s not a showstopper, unlike a requirement for a non-existent fairing, payload shroud, and/or bigger launcher.

I’m not knocking X-37. I hope we see (or at least milspace-types see) a lot more of it. But X-37 was never designed with crew in mind while HL-20 was. And, not surprisingly, the challenges to getting X-37 crewed are bigger than those on HL-20.

FWIW…

Anyway, I saw Vulture4’s comment and it was quick to answer, so what the heck. Had to do something while the papers were downloading.

Really I am not sure what point you’re trying to make. One day we’re looking at a 100 ton lifting body the day after it only is 9 ton. So what?

Why are you implying the SNC is taking landing matters lightly? Any evidence of that?

As I said earlier. Embarrassing. This is turning into a train wreck for your credibility. Sorry. You are putting forth all those allegations without one shred of evidence! Get a grip!

SNC, just like SpaceX and the others, is a private entity. They owe their technical design justifications to who ever is funding them. And if the SOW for NASA CCDev does not ask for landing characteristics then they don’t have to tell anyone outside their investors.

Do you really think these people below don’t know what they’re doing?

http://www.parabolicarc.com/2011/04/19/anatomy-ccdev-bid-dream-chaser/

Here:

http://www.nasaspaceflight.com/2011/08/nasa-ccdev-2-partners-reveals-progress-milestones/

“SNC are receiving unpublished amounts of money from their $80m award pot, following each successful completion of their 19 milestones, the latter of which is listed as the Free Flight Test, which will be a piloted Flight test from carrier aircraft to characterize handling qualities and approach and landing.”

X-38 was not designed to land on a runway. It was designed to land on near a flat area like a lakebed. It also was a very differnt kind of craft. It is smaller than the HL-20 designed to fit in the shuttlle’s payload bay.

HL-20 and Dreamcahser were both designed to land on a standard runway. They were not intended as emergancy escape craft but as crew transport. HL-20 could fit in the shuttle’s payload bay, but only with wings folded. It was designed to be launched by an expendable.

The lifitngbodies X-24, M2, and HL10 landed on a runway.

Seriously, both the NASA lifting bodies (none of which weighed even 3 metric tons at touchdown, while Dream Chaser is closer to 9MT) and the Shuttle land unpowered at around 200mph. It can be done, but there is very little margin. No one who has seen it done would say it should be tried with even less margin. Dream Chaser, if it lands on a runway, would be much heavier than any lifting body that has done so unpowered. That means it will have to be going much faster. Most of the Sierra Nevada documents are ambiguous on the point. Can you find _any_ document that says “The Dream Chaser will definitely not land with a parachute.”? While an Israeli F-15 did land after shearing off a wing when it collided with another aircraft during training, it was at nearly full power at touchdown.

I have noticed that the canted tail surfaces on the Dream Chaser seem a little flatter than those on the HL-20. Maybe they will flatten it out and add a small forward wing to get a little more lift. Everybody learns from experience. But one thing that experience teaches is that we should never make things harder than we have to. Aircraft always need as much lift as they can get, within the constraints of mass and drag. The tradeoff between wing-fuselage and lifting-body configuration should not be taken lightly, and should not be made based on intuition, appearance, tradition, or the challenge of doing something the hard way.

“A “lifting body” is an aerospace vehicle that does not have wings, generating lift from airfow around the fuselage alone.”

No it is not. A lifting body is a vehicle that derives most of its lift from the fuselage. And that’s it. Nothing more nothing less. If you take a Shuttle and look at its hypersonic lift, it is derived by its planform area. Wings have very little to do. Unlike most wings they have a flat bottom so to alleviate the heating. And that is it.

“No one has presented evidence that any lifting body can achieve an L/D at touchdown of greater than 4 or any runway landing, unpowered, at a realistic mass for a returning spacecraft.”

This is a very different statement. Most lifting body do indeed land at very high speed, just like Shuttle. And it is indeed very difficult if not impossible to land. However, I haven’t looked at the HL-20 aero and therefore will reserve my statement. Only that the vehicle has been analyzed for ever at NASA LaRC and at SNC. Why would NASA fund such a vehicle when they claim they can do even though they might not??? The vehicle mostly is a NASA developed vehicle nowadays. So unless and until I see the aero contradicting the fact it can land on a runway I will believe it can. Note that the vertical control surfaces are not really vertical so they might very well provide the necessary lift. It is nothing like a Shuttle in terms of mass and that might help too. As for X-37, I have no idea if it would scale up to a crew vehicle. I think yes since Boeing proposed it for OSP. BUT I don’t know if you can launch it as easily as the actual X-37. Yes it has wings, mostly what appears to be Shuttle like wings (save a lot of analysis on the various problem of shock-shock interaction and the likes).

The requirements on the bottom of the vehicles are driven by heating, not aerodynamics. We are not talking F-16 here, only a vehicle that can handle reentry and go somewhere to land.

Indeed a lifting body with parachutes, to me, makes a lot more sense. You can then have a lightweight vehicle that can sustain possibly high heating. Kliper has something to it. The BO biconic too. I wish I could tell you other story but I can’t.

“The final craft in the lifting body program, the Martin X-24B, was an Air Force design with small horizontal delta wings. ”

The sharp leading edge would be a killer on reentry.

Yes Shuttle has wings for some L/D, not all L/D. You could design a lifting body without wings with the same hypersonic L/D which is the one that counts for down/cross-range. The wings are only for runway landing and that is a fact. You could land a lifting body with parachutes/parafoil as demoed by the X-38.

X-38 was a very good idea. It got killed by nonsense. May not have been the best idea but heck it beat the heck of a lot of other concepts.

Shuttle is a lifting body at hypersonic speed where it counts. Tell you what. A capsule at an angle of attack is a lifting body just the same.

Hey Rick how’s this mountain retreat of yours going? Getting addicted to this I see…

Any how. vulture4 has been spouting nonsense for some time now. Too bad because I used to like his lines about Shuttle. But when he gets carried away into the Shuttle netherworld it becomes an embarrassment.

After all these years of investigations at NASA LaRC and SNC those people could not figure the Dreamchaser can, or not, land on a runway? Really? Not counting the BOR-4 predecessor.

Anyway I guess we’ll see if the thing can or not land on a runway… Soon hopefully.

If you would like an intelligent conversation, I would be happy to have one.

A “lifting body” is an aerospace vehicle that does not have wings, generating lift from airfow around the fuselage alone. I have been well acquainted with the concept since its genesis in the 60’s. I remember one of the first NASA presentations explaining the rational for this path. It was not supported by any meaningful trade study or aerodynamic analysis. In later years the HL-20, X-38 and similar concepts have been subjected to more careful aerodynamic analysis and some small changes made, but the basic constraint of not utilizing conventional planar airfoils has been retained.

Another poster had claimed the X-37 “does not scale” and that the HL-20 was a superior design. No one in this group has presented any evidence to support either of these points. No one has presented evidence that any lifting body can achieve an L/D at touchdown of greater than 4 or any runway landing, unpowered, at a realistic mass for a returning spacecraft.

The lifting body program began in the 60’s and was based on the premise that an entry vehicle could be constructed that could land on a runway without wings, The NASA lifting bodies all had rounded bottoms and relatively flat upper surfaces. I saw a NASA presentation that explained the theory behind this; a cone flying horizontally would have equal pressures on top and bottom. By removing the top half of the cone only the upward force on the bottom would remain. Of course this made no sense aerodynamically since the torques on the vehicle in the presentation were unbalanced, but that was long before CFD.

The final craft in the lifting body program, the Martin X-24B, was an Air Force design with small horizontal delta wings. The central fuselage completely inverted the NASA approach, with a completely flat bottom and a fuselage longitudinal cross-section not far from the classic “Clark Y” profile. The Shuttle has full conventional delta wings, both to allow for runway landing and to meet the DOD requirement for sufficient crossrange to land at the launch site after a single polar orbit.

According to NASA’s Commercial Crew website, Dream Chaser is supposed to land on a runway.
http://www.nasa.gov/offices/c3po/partners/sierranevada/index.html

Also, if it can’t land on a runway, why is it equipped with runway landing gear?
http://www.google.com/imgres?imgurl=http://msnbcmedia.msn.com/i/msnbc/Components/Photos/060622/060622_spaceship_hmed_11a.jpg&imgrefurl=http://cosmiclog.msnbc.msn.com/archive/2006/09/28/4985.aspx&h=301&w=468&sz=107&tbnid=nLVu3t2htYqbQM:&tbnh=90&tbnw=140&prev=/search%3Fq%3Ddream%2Bchaser%26tbm%3Disch%26tbo%3Du&zoom=1&q=dream+chaser&docid=Lv4wTefkbVWVAM&hl=en&sa=X&ei=VQVtTuz7KMmCtgejv_G-BQ&sqi=2&ved=0CDQQ9QEwAg&dur=169