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Possible Craft

Posted by: Sev - Sun Oct 10, 2004 4:10 pm
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Possible Craft 
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Post    Posted on: Mon Nov 08, 2004 2:04 pm
Ekkehard Augustin wrote:
So it will be interesting to see wether Scaled will go to orbit by modifying their Wight Knight/SpaceShipOne-air-launch-design, by SSTO, by another quite new air-launch-design or by doing the paradigm shift they consider to be required for ground-launch.


Yes. As much respect as I have for Rutan -- it's this quote that has me lowering my expectations that he will be successful at creating an orbital craft. Dunno -- the man is a genius -- I'm just an amateur with a space hobby.


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Post    Posted on: Mon Nov 08, 2004 2:10 pm
Why not looking at it by Vector Calculations?

One vector to represent the gravitational pull down to the surface - the length of this vector is diminishing by the square of altitude.

A second vector to represent the velocity the vehicle is orbiting by - the length of this vector is direct proportional to the velocity.

This way everyone can test it on a piece of paper for example - the gravitational acceleration of 9.81 m/s^2 can be used as a base-value.

This doesn't claim to be sufficient in physical or technical sense but it can serve as afirst approximation.



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)


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Post    Posted on: Mon Nov 08, 2004 2:15 pm
Let me begin with a good natured jab to the ribs ...
JamesHughes wrote:
ps. SOrry in advance for any spelling issues.

Ok, I can move on from the spelling issues. However ...

Apostrophes. Your use of them is catastrophic. For example ...
JamesHughes wrote:
Armadillos craft comes to mind.

Should be "Armadillo's craft comes to mind."

And now to return on topic ... I find myself in agreement with mrmorris, it's hard to believe that Rutan actually "believes" what he said ... it sounds more like a guy trying to keep everyone on the same track as he is (i.e. if it aint air-launch, it aint Rutan). Having the advantage of being the only show in town makes it easier to make such statements. I would be interested to know what Carmack's interpretations of Rutan's comment are.

DKH

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Post    Posted on: Mon Nov 08, 2004 2:37 pm
The spacecrafts to be built for Branson are reported to need modifications compared to SpaceShipOne. It will be interesting first to wait for these vehicles - they will be heavier because of the five-passenger-capacity. They can serve as the next technological step to the orbit - redesigns, further developments, experiences....



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Post    Posted on: Mon Nov 08, 2004 2:46 pm
Ekkehard Augustin wrote:
One vector to represent the gravitational pull down to the surface - the length of this vector is diminishing by the square of altitude.


The variation in the value of g changes by approximately 0.003% per 100 m altitude -- at least in the ranges being used here. The actual calculation is based on the distance from the center of mass -- but as the diameter of Earth is 12,756 kilometers -- at sea level we're already ~6,378 km from the COM. An air launch height of 60,000 meters will only be 6,438 km from the COM -- or a change of less than 1%.

So let's say we have a 10,000 kg craft a sea level. For an air launch that occurs at ~60,000 feet (20,000 meters) -- the weight reduction due to altitude would then be:

10,000kg - 10,000kg * (20,000 m * (.00003/100m) )
10,000kg - 10,000kg * (200 * .00003)
10,000kg - 10,000kg * .006
9,940kg

Somehow I don't see 60kg from a 10,000 kg craft prviding much incentive for an air launch.

Ekkehard Augustin wrote:
This way everyone can test it on a piece of paper for example - the gravitational acceleration of 9.81 m/s^2 can be used as a base-value.


Everyone except you, apparently.

Ekkehard -- are you in a special sort of economics that has no connection to mathematics? Finding the above information about the effects of altitude on g was a simple matter of putting the terms 'gravity altitude calculation' into Google.


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Post    Posted on: Mon Nov 08, 2004 2:58 pm
There seems to be a misunderstanding:

I proposed Vector Calculations only as an instrument for theorectical insights when you explained the reason why higher orbits have a slower 'straight-line' velocity - a way to look what would happen given a certain gravitational pull at alternative velocities.

My proposal had nothing to do with calculations of possible crafts, Bransons vehicles or SSO.

Sorry for the misunderstanding, mrmorris - the reason seems to be that you finished your post before mine was ready.



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EDIT: I'm good in Mathematics - without that I never would have got my university diploma.


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Post    Posted on: Tue Nov 09, 2004 7:43 am
There is a special detail that can be added to my proposal:

There's no need to keep orthonormality (for example 1km/s per 1 cm of the velocity vector AND 1km/s^2 (or the resulting velocity as its integral) per cm of the gravitational vector) - the normality can be removed to reduce to orthogonality (where the velocity vector can be kept as it is under normality but the gravitational vector can be changed to 10m/s^2 (or resulting velocity) per cm, 2,5m/s^2 (...) per cm or something else depending on what is appropriate for diagramm and graphic purposes.

The only purpose of the proposal is intuition and assistance for imagination - nothing else.



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Post    Posted on: Wed Nov 10, 2004 1:56 pm
Thanks MrMorris for the insight on kinetic and potential energy. Of course (meaning I should have realised this), at a certain orbital height you have a specific potential energy due to height (mgh) and also a specific kinetic energy according to velocity (1/2mv^2), and those added together would have to be the same no matter what method you take to get there, so therefor you would still need to same amount of propellant.

Apologies for atrocious use of apostrophies. WIll I never learn....

James


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Post    Posted on: Tue Nov 23, 2004 2:41 pm
What about making a small crew carrying orbital vessel using the RCC material mounted on the space shuttle's leading wing edges as a heat shield? Such a shield is obviously reusable and would require very little development to allow it to be applied on other vehicles.

I also like the parafoil landing technique used on the X-38 and combining this with the above heatshield technology on a small lifting body design (no more than 6 or 7m in length) could result in a feasable crew transfer vehicle. I have no figures for what the weight is likely to be but I would have thought that it could be built to be under 8,000kgs.

Such a vehicle should be small enough to launch on a range of current day boosters but large enough to have a small rocket engine and fuel tanks incorporated into the design to give an additional kick into orbit, if one was needed.

What do you think, is such a vehicle able to be built using current technology in a relatively short timescale or would it be to heavy to get off the ground?

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Post    Posted on: Tue Nov 23, 2004 9:00 pm
A few words about Rutan and SS1 that as far asI can tell have been overlooked in this discussion. First, I haven't read every single posting in entirety so if I repeat an earlier comment my apologies.

During Discovery's documentary on Rutan and his Xprize bid Rutan specifically discussed a tier 2 and tier 3 program. Tier 2 being orbital and tier 3 being beyond orbit. He then flashed designs up on the screen. Tier 1 was shown as the familiar few of SS1 slung under white knight. Tier 2 was depicted as an SS1 looking craft placed vertically on top of a booster. Tier three was either not shown or I can't recall it. Also, Rutan has said publicly (check out the space review) that he has lunar aspirations. This is proven in his work to form T/space and their bid on NASA's lunar architecture contract. Finally Rutan talked at length after Xprize flight 2 about the technical achievements of SS1. Not only did it go higher than the Bell x1 dreamed of going its reentry was much more benign. I seem to remember his numbers being something like this. Bell X1 upon reentry experienced 16,000lb per square inch whereas SS1 with its caregfree reentry experienced only 60lbs per square inch. Now I am no rocket scientist, but if Rutan's SS1 had such a benign suborbital entry why could in not with modification make an orbital reentry?? The evidence seems to suggest that Burt is headed in this direction. I know that SS1 seems small and spindly and like it would rip apart in a second, but it has succesfully survived sitting on top of a pretty powerful motor and its composite epoxy structure is extremely strong as well as naturally heat resistant.

Basically my question is does anyone really know whether it (or its derivative) wouldn't survive an orbital reentry? Everyone seems to think so, but I'm not so sure heat resistant technologies have come a long way despite what Nasa is able to accomplish.

Anyway looking forward to thoughts on this.

~CCCP

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Post    Posted on: Wed Nov 24, 2004 6:50 am
CCCP wrote:

>>Basically my question is does anyone really know whether it (or its derivative) wouldn't survive an orbital reentry? Everyone seems to think so, but I'm not so sure heat resistant technologies have come a long way despite what Nasa is able to accomplish.

I don't know much about new heat shielding methods, but remember that the difference between orbital velocity and what SS1 did is about 15,000 mph. You know those pictures of Columbia breaking up? It's shiny like a shooting star isn't it? That's because when you reenter at 17,000 mph the kinetic energy of your craft hitting the atmosphere heats the air around it to about (I think, I'm a layman too though) 54,000 degrees Farenheit, turning it into a plasma! Thus, while SS1's feathered reentry is an extremely elegant solution to suborbital reentry, for orbit you would need something a little more hardcore.


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Post    Posted on: Wed Nov 24, 2004 8:54 am
CCCP wrote:
snip
Finally Rutan talked at length after Xprize flight 2 about the technical achievements of SS1. Not only did it go higher than the Bell x1 dreamed of going its reentry was much more benign. I seem to remember his numbers being something like this. Bell X1 upon reentry experienced 16,000lb per square inch whereas SS1 with its caregfree reentry experienced only 60lbs per square inch.

Bell X1? Try X-15. If you cant remember a detail like that how can we put any trust in the numbers you claim to remember. Supporting links please.

I dunno I always thought soviet intelligence was more on top of the game than this.

CCCP wrote:
Basically my question is does anyone really know whether it (or its derivative) wouldn't survive an orbital reentry? Everyone seems to think so, but I'm not so sure heat resistant technologies have come a long way despite what Nasa is able to accomplish.

Everybody!? I can't remember anyone saying that SS1 (aka SSO) would survive a de-orbit. As yet there is no derivative.

Of course your syntax might be screwed up, lord knows it happens a lot around here, perhaps you meant to suggest that maybe SS1 might in fact survive re-entry but also that you doubt it. So basically you are asking "does anyone think this extremely unlikely thing is in fact likely" ... which is like asking a one-legged man to join you in an arse-kicking contest.

DKH

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Post    Posted on: Wed Nov 24, 2004 11:08 am
There are experiences only by three flights - all to apogees between 100 and 112 km. From these experiences it is known at which reentry velocities SSO is safe and which temperatures and forces it can survive.

There will be experimentally won data indicating the highest temperatures, strongest forces and fastets velocities SSO can survive. When I looked for these data I couldn't find them - they may be business- and technical secrest of Scaled/Mojave.

If these data were available publically it would be possible to compare them with those from the three flights. This comparison could show what improvements are required.

Launching SSO into the orbit would require at least one additional stage - this means that in principle it could be decelerated too by an additional stage down to velocities it could survive according to experienced or experimental data. SSO's own engine perhaps can be improved too.

Secretly Scaled/Mojave may be going a way similar to this - but they never will tell before they have an orbital vehicle - that's their policy.

So there are good reasons not to mention WK/SSO but to ask what's required to make SSO reentry from orbit safe and secure. This could tell us wether such an idea is realistic etc.



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Post    Posted on: Wed Nov 24, 2004 11:37 am
Ekke wrote:
Launching SSO into the orbit would require at least one additional stage - this means that in principle it could be decelerated too by an additional stage down to velocities it could survive according to experienced or experimental data. SSO's own engine perhaps can be improved too.

Eh? I don't know what you are talking about ... SSO (or SS1) is a suborbital vehicle. Proposed orbital vehicles have other names. Proposed vehicles do include a to-orbit additional stage as mentioned previously. Nobody else has suggested a SSO-derived vehicle would use a deceleration stage to deorbit, in fact I haven't read a single serious discussion on the viability of using rockets to decelerate from orbital speed to a velocity in tune with an SSO-style descent. What I have read is that such an idea is not workable (have to bring to orbit, unused, too much mass of fuel).

Ekke wrote:
Secretly Scaled/Mojave may be going a way similar to this - but they never will tell before they have an orbital vehicle - that's their policy.

Nonsense, they blared forth about their little suborbital vehicle well before they even lit the fire to it's engine. Well before it was, in fact, suborbital. What you mean is that they wont compromise their credibility until their risk assessments tell them that it's safe to let the cat out of the bag.

Ekke wrote:
So there are good reasons not to mention WK/SSO but to ask what's required to make SSO reentry from orbit safe and secure. This could tell us wether such an idea is realistic etc.

The only way SSO could make a re-entry from orbit is if the space shuttle (if it ever flies again) puts it into the cargo hold first. The only way SSO is going to orbit anyway is as a museum piece when the orbital Smithsonian opens its doors in 2235.

DKH

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Post    Posted on: Wed Nov 24, 2004 12:05 pm
Yes - it is not workable for economical reasons. Seen from today at least.

But I didn't read any reasons why it should be impossible for technical reasons yet.

The only technical ways to get SSO into an orbit all may be very suboptimal. And SSO is suborbital if it is launched as it has been at 21st of June, 29th of September and 4th of October.

But as it is docked to Wight Knight to be launched it could be docked to an additional stage by the same mechanism and technique.

So I didn't want to suggest to do so but only that it could be done. I didn't want to suggest a deceleration stage but only that it could be done in principle.

So is suborbital only but it could be made orbital at suboptimal high costs - it would be uneconomical. It would be cruel seen from the point of an economist at least.

But it isn't impossible in principle. An orbital vehicle made by Scaled/Mojave/Rutan will look quite different to SSO I suppose - but the technologies developed for SSO up to a certain reasonable degree wil be used in that vehicle too I think. Rutan will try to prevent as much R&D costs as possible -he will not invent the wheel twice.

As long as a name for an orbital vehicle made by Scaled etc. is missed "SSO" or "modified SSO" or "orbital SSO" and the like can be used as substitutes. We only shouldn't have in mind then the image of SSO we are used to.



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)

EDIT: Rutan himself has caused ideas to make SSO orbital by showing pictures and models of a modified SSO connected to boosters etc. This has been discussed at the board - and commented too. One of the comments was "Rutan's dreams" - so there is no reason not to look for ways to get SSO to the orbit - it's just dreaming, theorizing, thinking academically.


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