The Next Generation of Human Spaceflight

GIThruster · Post by **GIThruster** » Thu Oct 07, 2010 7:34 pm

Here's some interesting stuff on radiation hardened high def video camaeras:

http://www.advancedimagingpro.com/artic ... h_0907.pdf

even more interesting is a way to remove the camera parts away from the camera so much less of it has to be hardened:

http://www.thermoscientific.com/wps/por ... archType=0

If you want to check on these sorts of systems, it's worth checking the Stryker, since it has about 9 periscopes I believe? and no windows.

GW Johnson · Post by **GW Johnson** » Sun Oct 10, 2010 12:02 am

With a capsule-type craft, windows are only a little problem, as they face into a separated wake zone, as long as your attitude control cannot fail. My guess is that crew escape vehicles will be capsule-type craft for a long time to come. Things like that need human control as (at least) a backup, which means they need windows. The quartz panel solution works well enough.

It's lifting reentry craft that pose the problem. The shuttle showed us that windscreen transparencies are possible, but also just how critical attitude control can be (far more stringent than the capsule case). This would apply to lifting-body vehicles as well as winged vehicles.

It might be possible to ease the design quandary somewhat by going to very low wing loadings / ballistic coefficients instead of the very high values used today. That would put more of the deceleration higher up in the thinner air, earlier in reentry. From what I have heard, this increases the total integrated heat to be dealt with, but reduces peak skin temperatures. Myself, I dunno. Yet.

A lifting craft that does not need piloted control as a backup on ascent, could use a detachable heat shield over its windscreen during reentry. This allows pilot visibility for landing. If you need a piloted backup mode on ascent, you can't do this.

About the only other option I have thought of is the "stowable heat shield". You fly up with visibility, you have visibility on orbit. You occlude for reentry, but then re-stow the windscreen heat shield for visibility during piloted landing. It's like landing gear doors. There are weight and reliability problems to solve, but I sense nothing insuperable here.

Plus, there is always artificial / remote vision, as we have been discussing recently. I think a stowable windscreen heat shield, and some sort of artificial vision, are the two best concepts. But, that's just a good guess on my part.

rjaypeters · Post by **rjaypeters** » Sun Oct 10, 2010 6:51 pm

GW Johnson wrote:...I think a stowable windscreen heat shield, and some sort of artificial vision, are the two best concepts. But, that's just a good guess on my part.

I agree. I think synthetic vision, if it meets all kinds of requirements we have already discussed, should be primary. For simplicity, cost and weight reasons I'd prefer an ejectable windscreen heat shield for emergencies. Probably the safest would be a rocket deployed heatshield to get it away from all the delicate bits downstream.

BTW this would also be a good use for solid-fueled rockets, but that's another thread.

93143 · Post by **93143** » Sun Oct 10, 2010 8:02 pm

rjaypeters wrote:Probably the safest would be a rocket deployed heatshield to get it away from all the delicate bits downstream.

...and the rockets are pointing where?

Betruger · Post by **Betruger** » Sun Oct 10, 2010 9:16 pm

Naive/stupid question - Would putting those rockets near the circumference and tilting their exhaust outward not be good enough?

93143 · Post by **93143** » Sun Oct 10, 2010 9:22 pm

I thought of that. Maybe. It might depend on the nature of the emergency...

I can't answer this one without extensive analysis. A LAS engineer might be able to...

rjaypeters · Post by **rjaypeters** » Sun Oct 10, 2010 10:16 pm

93143 wrote:I thought of that. Maybe. It might depend on the nature of the emergency...

Emergency: Synthetic vision and instruments fail before landing. Challenge to imagination: how synthetic vision and instruments fail without taking flight controls with them. Upshot: emergency vision may not be worth the trouble.

Also, on the most recent NASA capsule, simultaneously-firing rim-mounted motors for lifting the capsule away from the stack was rejected because of timing difficulties. We'd probably have the same problem. A single motor is best and we'd need to arrange the exhaust to miss the windscreen, but engine intakes, etc. not as sensitive and could stand short exposure.

Betruger · Post by **Betruger** » Sun Oct 10, 2010 10:25 pm

93143 wrote:I thought of that. Maybe. It might depend on the nature of the emergency...

I can't answer this one without extensive analysis. A LAS engineer might be able to...

Just curious as a layman to the field - what are the main factors?

GIThruster · Post by **GIThruster** » Sun Oct 10, 2010 11:59 pm

I'm not following. Under what conditions would you ever want to eject a heat shield?

Betruger · Post by **Betruger** » Mon Oct 11, 2010 12:59 am

A windscreen's shield.

DeltaV · Post by **DeltaV** » Mon Oct 11, 2010 4:47 am

As a backup to the electronic visual system, you could have periscopes using prisms and/or fiber optics, like subs do (or did), but no electronics involved in imaging. The purely-optical backup system could have apertures with heat shield covers that never get removed, unless the primary electronic system fails. Then, all-analog pyrotechnics with battery/manual-switch backup, or mechanical cables/springs, would blow/eject the covers. The pilot then uses viewers which automatically drop down, or can be manually pulled into position if the auto-deploy fails. Piece of cake.

GIThruster · Post by **GIThruster** » Mon Oct 11, 2010 5:43 am

I see, but you then have all the weight of the window. If you're going to do that, put in a diamond window. No need to cover it. Diamond is the most thermally conductive material there is, it's strong and it's good to extremely high temps. Just can cost a bundle but if you're building spacecraft, I'm sure you can afford a mil to build a large diamond chemical vapor deposition chamber.

Don't think diamond needs a heat shield. The windows in the Shuttle are in a uselessly high position because we couldn't make diamond windows 30 years ago. Now we can.

93143 · Post by **93143** » Mon Oct 11, 2010 5:58 am

http://www.azom.com/details.asp?ArticleID=262 wrote:Diamond has limitations. It is meta stable at room temperature and pressure, forming a black coat when heated to above 600°C in oxygen and reverting to graphite when heated in nitrogen at around 1500°C.

I wonder how it would handle reentry?

Betruger wrote:
93143 wrote:I thought of that. Maybe. It might depend on the nature of the emergency...

I can't answer this one without extensive analysis. A LAS engineer might be able to...
Just curious as a layman to the field - what are the main factors?

Well, I'm more of a CFD guy; I don't have all that much formal aerodynamics experience, but here goes:

I doubt the vehicle's attitude control would be a major factor in a dynamic sense; compared to a window shield propelled by solid rocket motors, the spaceplane can probably be considered to be nonaccelerating. I could be wrong, of course...

The attitude itself, in a quasi-static sense, might be another story. That shield is essentially a flat plate with a high angle of attack, which could be extremely unstable. Even at nominal flight conditions, I'm not sure it would be controllable. Add in an unexpected flight condition, and the situation could get worse. (I'm making stuff up here; as I said, an expert in the field would be useful.)

Then there's the issue of ignition timing brought up by rjaypeters...

You do not want solid rocket exhaust impinging on the windows. Just ask the GSE team that worked Pad 39B after Ares I-X...

DaxG · Post by **DaxG** » Mon Oct 11, 2010 10:47 am

Space flight seems to be exciting but I think this will require lots of time before the government can approve it. Have you heard about Boer’s plan on pace tourism? For some its crazy but I think its not. Only that, it is so risky to make some tour on space. Aside from that, it will need too much fund. Well, I don’t know what comes through his mind about this idea but on the other hand, it is people’s right to be aware of what is space and to know more about the outer space.

rjaypeters · Post by **rjaypeters** » Mon Oct 11, 2010 3:15 pm

Ejectable windscreen heatshield: Single rocket motor mounted at the upstream end of the heatshield but oriented so the exhaust points downstream until the exhaust meets two tubes which turn the exhaust across and upstream of the local air flow (not incidentally away from the windscreen). The heatshield is track mounted so it will slide downstream and away from the vehicle once released. Before the rocket fires, pins are removed to allow the heatshield to slide. Rocket pulls heatshield downstream along the track and then away from the vehicle.

Eject the heatshield only when some semblance of stable flight is achieved. Rigging minimal flight controls while the electrical systems are down is the next fun challenge.