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21
Military / Re: Defense against Hypersonic Glide Vehicles
« Last post by sublight is back on Today at 12:12:59 pm »
.....seem to have quite enough problems dealing with normal atmospheric distortion and turbulence.

Only if they are coming from the terrestrial side....  ;)
22
Space Projects / Re: Stratolaunch
« Last post by martinbayer on Today at 12:10:09 pm »
Quote
delta winged orbiters with cryogenic rocket propulsion

Delta wing = heavy

Cryogenic propulsion: ISP red herring, cryogens makes tanks giant PITA.

I'd recommend to read the two papers and evaluate the specific designs and how those aspects were addressed, rather than make sweeping generalizations. It should go without saying that things like required wing and tank masses for the chosen design approaches were included in the mass budgets that resulted in the PMFs provided above. I'd also like to point out that Boeing is currently *building* the Phantom Express/XSP (Experimental SpacePlane), a delta winged reusable booster with LOX/LH2 rocket propulsion, for DARPA. The planned flight test program calls for 10 launches in as many days to demonstrate the viability of fast turn-around operations with cryogenic propellants. Boeing's design was the winner of a competition among three contending teams, and I doubt DARPA would have chosen an inferior concept with overweight wings and "PITA" tanks.
23
Space Projects / Re: Stratolaunch
« Last post by Archibald on Today at 12:06:13 pm »
Quote
delta winged orbiters with cryogenic rocket propulsion

Delta wing = heavy

Cryogenic propulsion: ISP red herring, cryogens makes tanks giant PITA.

24
Military / Re: Defense against Hypersonic Glide Vehicles
« Last post by Trident on Today at 11:44:16 am »
Said structures are operating in a thermal environment which is already challenging to begin with though, so there might not be a lot of margin to bear additional heat load. The straw which breaks the camel's back...

I do agree about the optical challenges imposed by hypersonic flow past the target - lasers currently seem to have quite enough problems dealing with normal atmospheric distortion and turbulence.
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Space Projects / Re: Stratolaunch
« Last post by martinbayer on Today at 11:36:55 am »
Once again, it comes down to the specific numbers of an actual design, i.e. whether the difference between the required 90% PMF and the ET like 96% PMF allows to integrate all required additional systems, modifications and load conditions plus a meaningful orbital payload.  for two examples of concept studies for reusable delta winged orbiters with cryogenic rocket propulsion and subsonic air launch separation at Mach 0.8 and about 9 - 10 kilometers altitude. .

 Neither of them are going to approach even 90% PMF

Both designs had an orbiter air launch mass of 250 metric tons, which exactly (and perhaps not coincidentally) corresponds to the Stratolaunch 'Roc' payload lift capacity, and both studies arrived at a corresponding orbital payload capability of around 7 metric tons to LEO.

yes, coincidental

True - the design specific analyses yielded total PMFs (including residuals and RCS/OMS propellants) of 0.855 and 0.843, respectively, which, while notably below 0.9, for the chosen and/or optimized propulsion systems, launch conditions, ascent trajectories, and target orbits, were in both cases found to be sufficient to achieve the stated payload performance.

Since you confidently assert that the Roc payload mass determination was coincidental to the sizing assumptions of both studies, did you take part in the Stratolaunch requirements definition process?
26
Vice versa... The Aerovan concept was the inspirationsource for the M.61 & M.62 freighters
according to 'Miles Aircraft'
覧覧覧覧覧覧覧覧覧

Which contributed to the still-born Hurel-Dubois-Miles 106 Caravan concept.
After that concept was transferred to Short Brothers, it eventually reached production as the Shorts Skyvan, my favourite skydiving platform!
27
Hi all! First post on the Forum)

Some words about Grokhovsky G-38.

It seems to me, that well known plans, images and 3d model that were posted by Redstar72 and blackkite are fake based on pic from the TM (Техника Молодежи) magazine 08 sep 1938.http://zhurnalko.net/=nauka-i-tehnika/tehnika-molodezhi/1938-08-09

But in fact this pic described as

Quote
Двух балочныйサ самолет, который демонстрировался на Парижской выставке. Хвостовое оперение приближено к крылу. Этот самолет переходная ступень к бесхвостым ォлетающим крыльямサ
or in Eng:
Quote
Two tail plane demonstrated on Paris air show [in 1936]. Aircraft tail moved closely to wing. This plane is intermediate stage to tailless "flying wings".

So this pic is just an "author`s vision" of Fokker`s G-1 performed by A. Preobrazhensky or S. Lodygin for article.

What a Fate`s joke: real Ivensen-Grokhovsky project replaced by fake, based on picture for (again) Grokhovsky`s article.

But in article about P.A. Ivensen i found another image of G-38 
http://sm.evg-rumjantsev.ru/des2/ivensen.html

And later - side view of G-38 in book Aircraft industry of USSR 1917-1945 part I (Самолетостроение в СССР 1917-1941 том 1) ch.5 p.245.

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Is the canard pivoted around a vertical hinge axis?
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Naval Projects / Re: Small Surface Combatant Task Force concepts
« Last post by TomS on Today at 10:55:50 am »
That slide deck also says "mature designs" but not explicitly "parent hull/design," which is interesting given that Austal's LCS-based design has changed pretty dramatically, HII still hasn't shown their hand, and now LockMart is teasing/hinting at a more dramatic departure from their base LCS design for their FFG(X) offering.

Hmm.  I feel like the hull may well be related to LCS-1 -- it's still got the large and very squared off flight deck that extends all the way aft.  But the superstructure is really different, much more like a conventional destroyer with a midships break and a very prominent raked tripod mast.  It may well owe something to Gibbs & Cox and their older International Frigate (which was considered for the Australian Air Warfare Destroyer).
The shape and fullness of the bow also look markedly different than LCS-1, I'm trying not too read too much into the silhouette but I definitely wouldn't be shocked if they gave it a more conventional displacement hull to improve ride and efficiency.

Given that the max speed regime is so radically different (26-28kts vs 40 knots), a new hull would certainly make sense for FFG(X).  That semi-planning hull only makes any sense if you need to push 40 knots.  But at that point, how is it a proven design if they've swapped out the hull, the superstructure, and most of the combat system? 

Even the Austal FFG(X) design seems to be stretching the definitions on this. Switching to Diesel/CP props from GT/waterjets is pretty radical.  The trimaran hull at least is still usable at lower speed regimes.

PS: I don't think they've replaced the "parent hull" language.  The reference to "mature designs" in the slide deck is about the purpose of the FY18 awards: Mature,  Reduce, and Identify are all action verbs there.  (They use the same construct in the present tense on slide 7: Matures, Reduces, Identifies.)
30
Space Projects / Re: Stratolaunch
« Last post by Byeman on Today at 10:50:48 am »
Once again, it comes down to the specific numbers of an actual design, i.e. whether the difference between the required 90% PMF and the ET like 96% PMF allows to integrate all required additional systems, modifications and load conditions plus a meaningful orbital payload.  for two examples of concept studies for reusable delta winged orbiters with cryogenic rocket propulsion and subsonic air launch separation at Mach 0.8 and about 9 - 10 kilometers altitude. .

 Neither of them are going to approach even 90% PMF

Both designs had an orbiter air launch mass of 250 metric tons, which exactly (and perhaps not coincidentally) corresponds to the Stratolaunch 'Roc' payload lift capacity, and both studies arrived at a corresponding orbital payload capability of around 7 metric tons to LEO.

yes, coincidental
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