Author Topic: SNC building test schedule for Dream Chaser – Dryden Drop Tests upcoming  (Read 84049 times)

Offline ChefPat

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Where is Stratolaunch on the modifications to their carrier aircraft? It would certainly be large enough to handle a Dreamchaser.
A long way from even being constructed.
Are they? They've had the 2 jets for more than ten months now. How long does it take to modify them?
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Offline Rocket Science

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Where is Stratolaunch on the modifications to their carrier aircraft? It would certainly be large enough to handle a Dreamchaser.
A long way from even being constructed.
Are they? They've had the 2 jets for more than ten months now. How long does it take to modify them?
It’s a whole new aircraft Pat. Only the engines and subsystems are from the donor aircraft.
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Offline RanulfC

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Based on what I'm hearing, it looks like there will be no drop test until late 2013- 2014. It takes time to adapt out a system and look at all possibilities. 
Sounds about right, maybe a little later depending...

I get the feeling some folks are not really "thinking" this all the way through :)

Attaching a jettisonable parachute to DC's tail, and dropping from high altitude by helicopter doesn't sound like the sort of thing that would take till late 2013, or does it?

I didn't actually "comment" on the original suggestion of this and I probably should have :)

You're not going to "need" to attach a "jettisonable" parachute to the DC-ETV, there is already one in place: the "drag" stabilization parachute :) They'd just have to move it from the current mounting (above the tether attach point) to a vehicle mounting point.

You're also not going to get QUITE that radical during the drop, (no "nose-at-the-ground" attitude) but you WILL eat up a lot of altitude generating enough "lift" overall to hit the "landing speed" targeted (191-knots/354kph/220mph) let alone higher. (Landing speed is noted here:
http://www.nasaspaceflight.com/2012/06/snc-dream-chasers-enterprise-test-approach/ )



The "issue" here is "dropping from high altitude" with a helicopter. Especially with the DC lifting body.

We've got several "facts" to work with already:
The stats for the Skycrane can be found here:
http://www.ericksonaircrane.com/

Note: Maxium "hook" weight is the important figure here. The S-64E can lift up to 9,072kg (20,000lbs) while the S-64F can lift up to 11,340kg (25,000lbs) with a "maxium" cruise speed of 115-knots (212kph/132mph) for the former and 104-knots (192kph/119mph) with the latter.

This is important for several reasons but the "biggie" is that these figures (for the Skycrane(s)) is for rather LOW altitude, well below 20,000ft. (As a comparison you can see the Shuttle A-and-L tests here, ya "wikipedia" I know but the general data is accurate, http://en.wikipedia.org/wiki/Approach_and_Landing_Tests :) )
The "highest" altitude recorded for the "type" for the S-64 is held by an earlier version for the US Army the "CH-54" which reached a maxium altitude of 36,000ft but this was with NO load, limited fuel/crew, no forward speed, etc so that it COULD reach that high. "Typical" maximum operational altitude is listed as a bit over 18,000ft but again that's NOT going to be with a full load, nor at "high" speed.

Helicopters like all "active" lift vehicles have a limit of what they can lift that goes DOWN with altitude, as does speed. (You have to trade "lift" power for speed power) So in general we're looking at a "probable" release at or around 10,000ft at most.

"Assuming" the DC-ETV mass' somewhat close to the "operational" launch mass of around 11,340kg the Helo flying it must be the F model which means a lower intial speed to start off with. If it's below 9,000kg they could use the E model but then the "flying" characteristics will be a lot different than the "actual" DC orbiter vehicle.

It could very easily be MORE than a year or two to get all the data needed to even see if they actually CAN use a helo to do "free-flight" drop tests for the DC-ETV. In general the DC-ETV has to "fall" fast enough, from high enough to generate a viable speed of almost 200-knots, (370kph/230mph) from a possible "maximum" drop speed of between 104 to 115-knots,(192kph/119mph to 212kph/132mph) and that's non-trivial.

As an example I'd point to the fact that NASA did this testing type mission when evaluating the low-speed handling characteristics of the "staight-wing" versus the "delta-wing" versions of the Shuttle. Most of them still ended up "pranging" the nose of the model pretty good because they simply couldn't generate enough lift from a zero-speed drop IIRC.
And that's a WINGED vehicle and not a lifting body :)


There are definately some low altitude / low speed tests they can do with the helicopter, including the first free-flight and landing tests.
Well "sort-of" at any rate...

The big factor is how far does it have to "fall" to get the needed speed to fly. With a landing speed of around 370kph/230mph and the vehicle length and width (span) which is listed as 8.84m (L) by 7.16m (W) and the mass of the vehicle which we probably should "assume" is near-flight weight of 11,430kg...

I think so. But if that's the case, what test(s) will a helicopter be insufficient for?
My take would be pretty much everything BUT a very limited "landing" speed test series and THAT only if all the numbers add up so that it can reach "minimum" speed within the altitude envelope available.

They really need a "carrier" aircraft for flight testing both to give it the intial minimum speed and a better altitude to work from. Which brings me to the idea of "hanging" the DC-ETV from a "normal" airliner mounting station. My take is its do-able as long as the station can be configured (a mounting pylon/bracket) and is able to handle the load. Which points to a particular issue; mass. Most of the engine weights I'm seeing do not exceed 4,000kg to 5000kg which is far below even the "low" estimated mass of the DC-ETV of 9,000kg. And that doesn't take into effect the mass of the "pylon" and mounting system. It's possible they could make a mount that would "span" say an inboard engine mount and the ferry engine mount but even then the total "weight" capacity of the mounts probably won't be enough to carry the load.

Now if the overall mass of the DC-ETV IS lower than anything listed they could very well use such an arrangment to test fly the vehicle HOWEVER the "tests" will be very far off the mark for any comparision to the "real-thing" because of the lift/drag/mass-ratio of the test vehicle.
(A low mass test vehicle will glide and generally fly much better than something that is close to the actual planned vehicle mass which would throw off any results)

Guess we'll have to wait and see.

Randy
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Offline Rocket Science

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10,000 will give us about 30 seconds flying time till touchdown... Wooo! 8)
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Online john smith 19

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The "issue" here is "dropping from high altitude" with a helicopter. Especially with the DC lifting body.

We've got several "facts" to work with already:
The stats for the Skycrane can be found here:
http://www.ericksonaircrane.com/

Note: Maxium "hook" weight is the important figure here. The S-64E can lift up to 9,072kg (20,000lbs) while the S-64F can lift up to 11,340kg (25,000lbs) with a "maxium" cruise speed of 115-knots (212kph/132mph) for the former and 104-knots (192kph/119mph) with the latter.

This is important for several reasons but the "biggie" is that these figures (for the Skycrane(s)) is for rather LOW altitude, well below 20,000ft. (As a comparison you can see the Shuttle A-and-L tests here, ya "wikipedia" I know but the general data is accurate, http://en.wikipedia.org/wiki/Approach_and_Landing_Tests :) )
The "highest" altitude recorded for the "type" for the S-64 is held by an earlier version for the US Army the "CH-54" which reached a maxium altitude of 36,000ft but this was with NO load, limited fuel/crew, no forward speed, etc so that it COULD reach that high. "Typical" maximum operational altitude is listed as a bit over 18,000ft but again that's NOT going to be with a full load, nor at "high" speed.

Helicopters like all "active" lift vehicles have a limit of what they can lift that goes DOWN with altitude, as does speed. (You have to trade "lift" power for speed power) So in general we're looking at a "probable" release at or around 10,000ft at most.

"Assuming" the DC-ETV mass' somewhat close to the "operational" launch mass of around 11,340kg the Helo flying it must be the F model which means a lower intial speed to start off with. If it's below 9,000kg they could use the E model but then the "flying" characteristics will be a lot different than the "actual" DC orbiter vehicle.
That looks like the big problem with drops from helicopters (even big ones). It looks like the only way to make this work is to use the hybrid rocket
Quote
It could very easily be MORE than a year or two to get all the data needed to even see if they actually CAN use a helo to do "free-flight" drop tests for the DC-ETV. In general the DC-ETV has to "fall" fast enough, from high enough to generate a viable speed of almost 200-knots, (370kph/230mph) from a possible "maximum" drop speed of between 104 to 115-knots,(192kph/119mph to 212kph/132mph) and that's non-trivial.

As an example I'd point to the fact that NASA did this testing type mission when evaluating the low-speed handling characteristics of the "staight-wing" versus the "delta-wing" versions of the Shuttle. Most of them still ended up "pranging" the nose of the model pretty good because they simply couldn't generate enough lift from a zero-speed drop IIRC.
And that's a WINGED vehicle and not a lifting body :)

My take would be pretty much everything BUT a very limited "landing" speed test series and THAT only if all the numbers add up so that it can reach "minimum" speed within the altitude envelope available.
[/quote]
So better than nothing but unlikely to deliver the full envelope needed?

Quote
They really need a "carrier" aircraft for flight testing both to give it the intial minimum speed and a better altitude to work from. Which brings me to the idea of "hanging" the DC-ETV from a "normal" airliner mounting station. My take is its do-able as long as the station can be configured (a mounting pylon/bracket) and is able to handle the load. Which points to a particular issue; mass. Most of the engine weights I'm seeing do not exceed 4,000kg to 5000kg which is far below even the "low" estimated mass of the DC-ETV of 9,000kg. And that doesn't take into effect the mass of the "pylon" and mounting system. It's possible they could make a mount that would "span" say an inboard engine mount and the ferry engine mount but even then the total "weight" capacity of the mounts probably won't be enough to carry the load.
And that's before you take into account the mounting hardware. An 11 000Kg vehicle would suggest an engine in the 55 000 to 110 000 Kg thrust range. Does anyone have such an engine? Wikipedia says the GE90 is the biggest in the world at 16644lb, but that's nowhere near big enough.
Quote
Now if the overall mass of the DC-ETV IS lower than anything listed they could very well use such an arrangment to test fly the vehicle HOWEVER the "tests" will be very far off the mark for any comparision to the "real-thing" because of the lift/drag/mass-ratio of the test vehicle.
(A low mass test vehicle will glide and generally fly much better than something that is close to the actual planned vehicle mass which would throw off any results)
It does not seem there is an engine big enough (that can be wing carried) that this can replace.
<sigh> It's such a nice idea, and it opens up the range of aircraft that could be used if you have a small enough vehicle to accommodate and it can operate entirely autonomously (no special wiring, no special plumbing).
Too bad. Firing the hybrid looks like the simplest option to get decent altitude and speed.
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Offline GClark

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On the subject of dropping lifting bodies from helicopters...

It's not like we have no experience doing this.  Anyone remember Project Parawing?  Hyper-X?  X-40A?  All dropped from helicopters at rather modest altitudes - all landed without incident (In the case of the X-40A multiple times).  We (the metaphysical we) know how to do this.

IMNSHO, much ado about nothing.

Offline Rocket Science

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On the subject of dropping lifting bodies from helicopters...

It's not like we have no experience doing this.  Anyone remember Project Parawing?  Hyper-X?  X-40A?  All dropped from helicopters at rather modest altitudes - all landed without incident (In the case of the X-40A multiple times).  We (the metaphysical we) know how to do this.

IMNSHO, much ado about nothing.

It’s not that it’s a problem... It only useful for a small part of the flight test envelope... For a manned high key approaching the HAC you would really need to be in stable flight at a higher altitude and velocity.
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Offline adrianwyard

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In a DC thread some time ago people expressed doubt that one nozzle design could be chosen that would work in vacuum and the atmosphere. I'm not sure if this is in fact that big a problem (shuttle SRM nozzle operated from 0-146K ft without trouble) but if it is, then the hybrids couldn't be used for drop tests

Offline Rocket Science

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In a DC thread some time ago people expressed doubt that one nozzle design could be chosen that would work in vacuum and the atmosphere. I'm not sure if this is in fact that big a problem (shuttle SRM nozzle operated from 0-146K ft without trouble) but if it is, then the hybrids couldn't be used for drop tests

I don’t buy that... SS1 Flew just fine and SS2 will use a similar motor to DC...
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Offline adrianwyard

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I don't buy it either. While SS1 started the burn at 50K ft, if the ground tests used the flight nozzle then it clearly runs fine at all altitudes. Perhaps hybrid motor nozzles are less sensitive to expansion ratio issues than others, or the performance losses are simply accepted.

If the RCS can also operate at all altitudes, then technically DC doesn't  need any carrier aircraft at all for low altitude tests: back it up to the end of a long runway, fire the hybrids, then at ~200mph fire the down RCS jets to pick the nose up, fly for a few seconds, cut the hybrids and land. Note: this is not a a serious suggestion, but it certainly would be fun to see tried!

« Last Edit: 12/30/2012 06:33 am by adrianwyard »

Offline kkattula

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...
If the RCS can also operate at all altitudes, then technically DC doesn't  need any carrier aircraft at all for low altitude test: back it up to the end of a long runway, fire the hybrids, then at ~200mph fire the down RCS jets to pick the nose up, fly for a few seconds, cut the hybrids and land. Note: this is not a a serious suggestion, but it certainly would be fun to see tried!


I don't know if the undercarriage can take a fully loaded DC. I really doubt the nose skid is practical for a take-off roll. :)

And RCS is not needed.  DC has aero controls.

But why horizontal take-off at all?  DC's abort mode is VTHL. And IIRC the motors provide up to 1300 m/s delta v. Why not just launch vertically to a reasonably high altitude and pitch over to gain some horizontal velocity before burn out?

« Last Edit: 12/30/2012 06:38 am by kkattula »

Offline adrianwyard

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Well yes, if we're just joking around (I started it) then it's only slightly more crazy to start with a vertical launch abort-style test.

Heading back to reality:

It sounds like the best guess is a helicopter will be used for low speed low altitude tests. For higher speed tests, we may have wait quite a while until SNC is ready to install/fire the hybrids or design/qualify mounts for an as yet unknown carrier aircraft.

I wonder which of these two is more likely to happen first.
« Last Edit: 12/30/2012 06:57 am by adrianwyard »

Offline thomasafb

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I seem to remember that in the late 1990s, the DLR made a drop test with a scale model of the Orbiter from an high altitude balloon (in Sweden?). Must have been a test to validate such a capability for Hermes or some other still-born European project. IIRC, the orbiter was remote controlled (and hit a building).

Not sure what came out of the test, but without the availability of a carrier aircraft, dropping DC from a balllon (at least for unmanned drop tests) might be an option.
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Online john smith 19

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It sounds like the best guess is a helicopter will be used for low speed low altitude tests. For higher speed tests, we may have wait quite a while until SNC is ready to install/fire the hybrids or design/qualify mounts for an as yet unknown carrier aircraft.

Well the hybrids are a fairly well characterized system and SNC have a relationship with the suppliers.

The high altitude balloon drop is starting to look almost sensible.  :)
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Offline adrianwyard

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It sounds like the best guess is a helicopter will be used for low speed low altitude tests. For higher speed tests, we may have wait quite a while until SNC is ready to install/fire the hybrids or design/qualify mounts for an as yet unknown carrier aircraft.

Well the hybrids are a fairly well characterized system and SNC have a relationship with the suppliers.

The high altitude balloon drop is starting to look almost sensible.  :)

Aren't SNC themselves the developers of the hybrids? It sounds cavalier to suggest hybrids be fired early on in the test program (see SS2's large number of unpowered flights) but if the DC motor is as ready for flight testing as the airframe and avionics, then I guess it wouldn't be insane.

Offline Rocket Science

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It sounds like the best guess is a helicopter will be used for low speed low altitude tests. For higher speed tests, we may have wait quite a while until SNC is ready to install/fire the hybrids or design/qualify mounts for an as yet unknown carrier aircraft.

Well the hybrids are a fairly well characterized system and SNC have a relationship with the suppliers.

The high altitude balloon drop is starting to look almost sensible.  :)

Aren't SNC themselves the developers of the hybrids? It sounds cavalier to suggest hybrids be fired early on in the test program (see SS2's large number of unpowered flights) but if the DC motor is as ready for flight testing as the airframe and avionics, then I guess it wouldn't be insane.
There is that old expression “that necessity is the mother of invention”. Since SNC has had the rug pulled out from under them by SCALED/VG they have to alter their test program. Sometimes “a giant leap” is required is required to overcome what might seem like a setback which propels you ahead (pun intended) recall Apollo 8 around the Moon. This is what is great about the private sector is that they can be agile in their approach rather than just generating a lot of studies and PowerPoints... I look at this as an opportunity to shine...
« Last Edit: 12/30/2012 12:50 pm by Rocket Science »
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Offline Jim

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I'm not sure if this is in fact that big a problem (shuttle SRM nozzle operated from 0-146K ft without trouble) 

146k does not qualify as vacuum. 

Offline Jim

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I don’t buy that... SS1 Flew just fine and SS2 will use a similar motor to DC...

Not relevant or applicable.

Offline Jim

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If the RCS can also operate at all altitudes,


No such thing.

Offline Rocket Science

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I don’t buy that... SS1 Flew just fine and SS2 will use a similar motor to DC...

Not relevant or applicable.
Jim, a question... Cannot SNC fit whatever sized nozzle to which ever part of the flight envelope they wish to test? It is a bolt-on operation...
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