Subject: Space-tech Digest #108 Contents: NASP/DCX risk (1 msg) Shuttle abort modes (4 msgs) DCX reentry heat protection (11 msgs) ------------------------------------------------------------ Date: Mon, 23 Mar 92 20:55 GMT From: CSG0669@vax2.queens-belfast.ac.uk (Dale Amon) To: space-tech@cs.cmu.edu Subject: Re: In opposition to airbreathing SSTO Sender: mnr@DAISY.LEARNING.CS.CMU.EDU When talking about technology risk, I really don't see how one can say the NASP is less risky than DCX. (or NDV than DC-1). DC does not push any envelopes, does not require any advances. It is pure engineering, all development, no research. NASP, on the other hand: 1) Requires designing the entire airframe as part of the engine inlet. 2) Requires SCRAM jets 3) Requires multiple engine regimes. 4) Requires active cooling by running capillary H2 lines all through the skin in areas prone to severe heating. 5) Requires materials technology at the edge. 6) Runs materials at very high temperatures. This tends to age the airframe at a high rate. NASP is science, all research and little development. There may be useful fallouts from it, but I don't think one of them is a near term civil spacecraft. There are other problems that are not addressed. 1) NASP gets you to orbit. DC gets you back to the moon, it gets you to near earth asteroids (given a scale up to carry the consumables which, if necessary is simple for this class of vehicle. Max specifically said that it scales nicely) 2) NASP technology will most likely get used for a space-fighter long before we see any civilian use. 3) Concorde is not even allowed to overfly most places, is limited to going supersonic over the ocean. This limits where NASP can fly, EVEN if FCC certified. DC goes straight up, making the problem much less severe. I've said it before and I'll say it again and again. You can't land NASP on the moon. Earth is the ONLY place that a NASP is of any use at all. - Dale ------------------------------ Date: Mon, 23 Mar 92 20:26 GMT From: CSG0669@vax2.queens-belfast.ac.uk (Dale Amon) To: space-tech@cs.cmu.edu Subject: RE: Space-tech Digest #105 > Just replacing the SRB's with something that could be shut down > would increase the odds on surviving a return to launch site (RTLS) > abort by quite a bit. This is a maneuver that's so risky NASA's never SRB's and RTLS are not related matters, except that RTLS cannot begin until the SRB SEP. SRB SEP time cannot be changed. Remember, there is no escape from the shuttle from SRB ignition until SRB SEP. You crosses your fingers and you prays... Dale ------------------------------ Date: Tue, 24 Mar 92 11:58:21 PST From: gwh@lurnix.COM (George W Herbert) To: space-tech@cs.cmu.edu Subject: Re: Space-tech Digest #105 Dale Amon writes: >> Just replacing the SRB's with something that could be shut down >> would increase the odds on surviving a return to launch site (RTLS) >> abort by quite a bit. This is a maneuver that's so risky NASA's never >SRB's and RTLS are not related matters, except that RTLS cannot begin >until the SRB SEP. SRB SEP time cannot be changed. Remember, there is no >escape from the shuttle from SRB ignition until SRB SEP. You crosses your >fingers and you prays... Saying that they are not related when the SRB's prevent that (the only) escape mode during the most dangerous part of the flight is sort of a funny distinction. I've heard tell of astronauts unauthorizedly planning for jettison-the-stack maneuvers. Apparently, over some of the envelope this can be done w/o destroying the shuttle. Higher ups apparently don't want to think about the idea, though. [Note that this story is unconfirmed and some details of it have been shown to be implausible before on the net, but the story may still have a base in truth. _I_ don't know for sure 8-) ] -george william herbert gwh@lurnix.com gwh@ocf.berkeley.edu ------------------------------ Date: Wed, 25 Mar 92 10:55:24 CST From: ssi!lfa@uunet.UU.NET (Louis F. Adornato) To: uunet!cs.cmu.edu!space-tech@uunet.UU.NET Subject: Shuttle abort modes George William Herbert (gwh@lurnix.com) writes: > I've heard tell of astronauts unauthorizedly planning for > jettison-the-stack maneuvers. Apparently, over some of the > envelope this can be done w/o destroying the shuttle. > Higher ups apparently don't want to think about the idea, though. > [Note that this story is unconfirmed and some details of it have > been shown to be implausible before on the net, but the story > may still have a base in truth. _I_ don't know for sure 8-) ] These sorts of stories apparently started with Lee Corey's "Shuttle Down", which described the use of an "unathorized" short field landing maneuver. It makes for a nice story, but it's nonsense. First, there's no way, especially post-Rodgers, that a flight crew could do "unauthorized" training - simulator time is just too scarce to screw around. Given the small army of people needed to operate the simulators, the inspector general would be on them like ugly on a frog. Besides, but it wouldn't do the crew that much good to have a procedure ready that mission operations wasn't familiar with. Second, there's no need - not only is NASA management the biggest bunch of professional paranoids on the planet (half of them spend thier time dreaming up worst case scenarios, the other half spend thier days trying to find workarounds), but the crew procedures office is controlled by the flight crew operations directorate. Contingency flight rules for ascent are mapped out to the milisecond, and, yes, there are several points in the plan where certain failure modes result in loss of vehicle. These holes are smaller than they where pre-Challenger, but they're still there. Anything that might save an orbiter and crew, especially something as cheap as a new crew procedure, is considered seriously. If you could present evidence that singing bluegrass on the flight deck would prevent problems, you can bet that someone would be flight certifying a banjo within an hour. A powered (SRB) sep maneuver _is_ theoretically possible; the primary software supports it and the hardware is in place. Certainly no one is eager to try it out in reality. Jettisoning the tank, however, would commit the crew to a TAL or a contingency abort - an RTLS can only be initiated while at least one main engine is firing. The maneuver requires that the Shuttle perform a "powered pitchover" (which looks a lot like the first half of an inverted loop), fly into it's own plume until it's heading back towards the cape, pitch up if necessary to gain glide altitude and speed, then shut down the engines, pitch down, jettison the tank. Lou Adornato | "When in trouble/ When in doubt Supercomputer Systems, Inc | Run in circles/ Scream and shout" Eau Claire, WI | The secretary (and the rest of the company) uunet!ssi!lfa or lfa@ssi.com | have disavowed any knowledge of my actions. ------------------------------ Date: Wed, 25 Mar 92 10:25:01 PST From: gwh@lurnix.COM (George W Herbert) To: gwh@lurnix.COM, lfa@ssi.com Subject: Re: Shuttle Abort Modes Cc: space-tech@cs.cmu.edu Actually, I heard this one a year before "Shuttle Down" serialized in Analog, and have continued to hear rumblings from inside. Again, I have no idea about the accuracy... I haven't had a chance to quiz any actual flight crew (pilot/commander) about it. The Payload Specialist I asked about it got a queasy look and said that it wasn't in the manuals, per se, and changed the subject. I suspect that the actual plan was that if they had a SRB or tank problem up to about 2/3 of the way to max Q they'd use the emergency tank release command and plan on ditching. Just let the whole ET/SRB stack fly out from under you... -george william herbert gwh@lurnix.com gwh@ocf.berkeley.edu ------------------------------ Date: Tue, 24 Mar 92 15:21:00 CST From: ssi!lfa@uunet.UU.NET (Louis F. Adornato) To: uunet!cs.cmu.edu!space-tech@uunet.UU.NET Subject: DCX reentry heat protection Does anyone care to go into more detail on the water-based heat protection system that someone (Henry?) mentioned in re: my query on DCX basics? Is this an active system (tanks, pumps, valves, outlet manifolds and orifices), or a passive system (water trapped or encapsulated in some vaccum-proof medium and surrendered under the heat of reentry)? In either case, this sounds like "new" technology to me - it's certainly something that hasn't flown before. Also, have they _really_ not made the decision yet? If first flight is in a year, I would think they'd already be cutting metal; it's pretty late to be making basic configuration decisions like this. In fact, this is going to have a big enough impact on operational costs that I don't see how anyone could make projections without knowing how this basic question was going to be resolved. Lou ------------------------------ Date: Wed, 25 Mar 92 08:13:48 CST From: ssi!lfa@uunet.UU.NET (Louis F. Adornato) To: uunet!cs.cmu.edu!space-tech@uunet.UU.NET Subject: Re: DCX reentry heat protection The following paragraph will be considered by some to be raising the signal to noise ratio on a list devoted to technology. I apologize in advance. Feel free to skip down to the "flame". I _really_ hope the DC-X and DC-Y are phenominal successes. I suspect that the fate of humanity may eventually hang in the balance. I _don't_ like the Shuttle, and I _don't_ like being a wet blanket. BUT... I was one of the people who thought that the Shuttle would get to a mission a month, would break the $1/kG barrier, and would finally open the door to space exploration. I went into college thinking that, by the time I got out, there would be a real space program again, and maybe eventually a shot at flight crew. Then reality set in. These days, every time I hear about how wonderful the next generation of vehicles is going to be, I think of the claim that IBM made when it introduced FORTRAN; "Programming is obsolete". These where the _same_ claims made by the Ada advocates. None of this should be interpreted as meaning that I think that the DC development and NASP research should be halted - I'm just trying to inject what I see as healthy skepticism into an otherwise euphoric discussion... From zoo.toronto.edu!henry (Henry Spencer) > >... In either case, this sounds like "new" technology to me - > >it's certainly something that hasn't flown before... > > Water cooling is not exactly new technology; given that heat dissipation > requirements are understood, I don't see anything in this that requires > radical innovation. It hasn't flown on spacecraft, but it's routine > down here on Earth. > Insulation isn't a new technology, either, and look how well it's worked on the Shuttle. It's the implementation that's the question. If this is going to be an active system, it introduces a fail operational element into the system design (i.e., it has to fail in such a way that it can still be operational, there can be no common mode failures on the redundancies, etc). Even if it's passive, it's definitely introducing a new implementation, and the claim of "no new technology" might as well have been made by Bush. > >Also, have they > >_really_ not made the decision yet? If first flight is in a year, I > >would think they'd already be cutting metal... > > DC-X, to fly next year, is the suborbital demonstrator. It doesn't need > heat protection. Several people have pointed that out, and thanks to all. But what about DC-Y? The thermal protection system is a key system component, which apparently hasn't progressed beyond the "then a miracle happens.." stage. I'm not saying that the design should be frozen (early design freezes have bought NASA a lot of headaches), but it should at least be "slushy" before anyone starts broadcasing projections on operating costs or turnaround times. Without at least a handle on the final system configuration, any such pronouncements are at least 80% wishful thinking. Keep in mind that even if every subsystem is simplified, bullet proofed, and line replaceable, there's still going to be tens of thousands of parts in the completed system. Of these, it'll only take a few clinkers to turn the whole system into another albatross. And now for something constructive, perhaps to be answered by someone who knows Hunter personally: Has anyone involved with this project made a thorough and methodical study of NASA's maintenance and logistics records for the Shuttle fleet? There's ten years of data there that _might_ be able to point up components, design elements, or manufacturing techniques that should be avoided (or adopted) in the next generation. I say "might" because to my knowledge, there is no consistant "long pole" in the Shuttle turnaround process. According to the evangelists of Statistical Product Control, this indicates a system that is "out of control", i.e. a process that isn't well enough understood or constrained to support systematic optimization. Nonetheless, I'd hate to see the Shuttle become the Viet Nam of space exploration - everyone too embarassed by the defeat to listen to the lessons learned by the soldiers. Lou Adornato | "If I'd known I was going to live this long, Supercomputer Systems, Inc | I'd have taken better care of myself" Eau Claire, WI | The secretary (and the rest of the company) uunet!ssi!lfa or lfa@ssi.com | have disavowed any knowledge of my actions. ------------------------------ From: henry@zoo.toronto.edu Date: Tue, 24 Mar 92 17:30:37 EST To: space-tech@cs.cmu.edu Subject: Re: DCX reentry heat protection >... In either case, this sounds like "new" technology to me - >it's certainly something that hasn't flown before... Water cooling is not exactly new technology; given that heat dissipation requirements are understood, I don't see anything in this that requires radical innovation. It hasn't flown on spacecraft, but it's routine down here on Earth. >Also, have they >_really_ not made the decision yet? If first flight is in a year, I >would think they'd already be cutting metal... DC-X, to fly next year, is the suborbital demonstrator. It doesn't need heat protection. Henry Spencer at U of Toronto Zoology henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: Tue, 24 Mar 92 20:28:46 EST From: John Roberts Disclaimer: Opinions expressed are those of the sender and do not reflect NIST policy or agreement. To: space-tech@cs.cmu.edu Subject: Re: DCX reentry heat protection >Date: Tue, 24 Mar 92 15:21:00 CST >From: "Louis F. Adornato" >To: uunet!cs.cmu.edu!space-tech@uunet.uu.net >Subject: DCX reentry heat protection >Does anyone care to go into more detail on the water-based heat >protection system that someone (Henry?) mentioned in re: my query on I'm not sure DCX is going to go high enough for heat protection to be a problem. John Roberts roberts@cmr.ncsl.nist.gov ------------------------------ Date: Tue, 24 Mar 92 17:55:52 -0800 From: George William Herbert To: space-tech@cs.cmu.edu Subject: Re: DCX Heat John Roberts says: >I'm not sure DCX is going to go high enough for heat protection to be a >problem. Two clarifications of this. One, DC-X won't be going anywhere near orbital velocity. It's just a structural, propulsion, and operations testbed for the concept (or was last I had a good look at it). Thus, it won't have to worry about reentry heating. The operational orbital vehicles to (hopefully) follow will have a significantly reduced thermal load due to very low mass/area loading or sectional density. As a result, they'll slow down very quickly at relatively high altitude, with significantly less thermal load on the vehicle. This is the same trick the second generation shuttleoid NASA keeps looking at (the flyback liquid booster, dual flying brick idea) was going to use to eliminate thermal tiles. -george william herbert gwh@lurnix.com gwh@ocf.berkeley.edu ------------------------------ Date: Wed, 25 Mar 92 03:15 GMT From: Karl Dishaw <0004244402@mcimail.com> To: space-tech Subject: DCX I've been trying to follow the Delta Clipper closely. Here's the best articles I've found so far. The second one has quite a few specs. SDI Organization Plans 1994 Test Flight Of SSTO Spacecraft JAMES R. ASKER 11/05/90 AW&ST, Vol. 133, No. 19, Pg. 26 Delta Clipper Partners Set Goal For Single-Stage-to-Orbit Vehicle EDWARD H. KOLCUM 02/03/92 AW&ST, Vol. 136, No. 5, Pg. 55 Karl ------------------------------ From: "Allen W. Sherzer" Subject: Re: DCX reentry heat protection To: space-tech@cs.cmu.edu Date: Wed, 25 Mar 92 8:41:57 EST > Does anyone care to go into more detail on the water-based heat > protection system that someone (Henry?) mentioned in re: my query on > DCX basics? All I know about it is from the assessment done by the Aerospace Corporation. The vehicle they looked at came in bottom first (like a typical capsule) and used water to cool the hear shield. It all looked pretty simple. However the assessment found that active cooling of the vehicle they assessed (which is not DC-Y) is at best a wash. The weight of the water and mechanism was just as much as a hevier heat shield. In addtiton, the pumps and pipes needed to make it work would make access to the engines far more complex which would add to downtime for maintenance. For this reason they concluded that the vehicle they assessed should not be active cooled. For DC-Y however which comes in head first active cooling may be a viable solution since it shouldn't affect maintenance. However, I think some of the NASP materials can take the thermal load so it may not be needed. Allen + They're just jealous because they don't have three + | wise men and a virgin in the whole organization | | --Vincent Cianci on the ACLU suit to remove a nativity scene | +----------------------410 DAYS TO FIRST FLIGHT OF DCX----------------------+ ------------------------------ Date: Wed, 25 Mar 92 16:17:48 -0600 From: ewright@bach.convex.com (Edward V. Wright) To: ssi!lfa@uunet.uu.net, cs.cmu.edu!space-tech@uunet.uu.net Subject: Re: DCX reentry heat protection >Several people have pointed that out, and thanks to all. But what >about DC-Y? The thermal protection system is a key system component, >which apparently hasn't progressed beyond the "then a miracle >happens.." stage. There are a number of options to choose from. Thermal protection was not considered a major issue for the Shuttle until after it was redesigned, doubling the size of the payload and the vehicle as a whole, to meet DoD requirements. Gary Hudson planned to use a water-cooled (transpirational) aluminum heat shield for the Phoenix. Max Hunter considered this along with several other options for SSX, which became Delta Clipper. The articles I saw when McDonnell Douglas was awarded the DC contract indicated that a final decision had not yet been made. However, the current issue of Final Frontier has an article on the Delta Clipper which indicates that McDonnell Douglas now intends to use carbon-carbon composite for thermal protection. The McDAC artist's conception that accompanies the article shows dark material, presumeably carbon-carbon, covering the vehicle from the nose about 2/3 of the way down to the base. ------------------------------ Date: Wed, 25 Mar 92 16:27:14 -0600 From: ewright@bach.convex.com (Edward V. Wright) To: aws@iti.org, space-tech@cs.cmu.edu Subject: Re: DCX reentry heat protection >All I know about it is from the assessment done by the Aerospace >Corporation. The vehicle they looked at came in bottom first (like >a typical capsule) and used water to cool the hear shield. It all looked >pretty simple. I believe this was an evaluation of Pacific American's Phoenix. Gary Hudson chose water-cooling for the Phoenix because it would permit the heat shield to be built out of the same materials as the rest of the vehicle. ------------------------------ Date: Thu, 26 Mar 92 08:14:30 EST From: John Roberts Disclaimer: Opinions expressed are those of the sender and do not reflect NIST policy or agreement. To: space-tech@cs.cmu.edu Subject: Re: DCX reentry heat protection >Date: Wed, 25 Mar 92 08:13:48 CST >From: "Louis F. Adornato" >Subject: Re: DCX reentry heat protection >The following paragraph will be considered by some to be raising the >signal to noise ratio on a list devoted to technology. I apologize in >advance. Feel free to skip down to the "flame". As you point out, it's a little out of place in space-tech, and needs to be discussed in sci.space. Are you sure you can't post there? I think your message on NASA press kits (that Henry reposted) also made it to sci.space direct, though you may have received an error message. >I _really_ hope the DC-X and DC-Y are phenominal successes. I suspect >that the fate of humanity may eventually hang in the balance. I >_don't_ like the Shuttle, and I _don't_ like being a wet blanket. >BUT... I was one of the people who thought that the Shuttle would get >to a mission a month, would break the $1/kG barrier, and would finally >open the door to space exploration. >These >days, every time I hear about how wonderful the next generation of >vehicles is going to be, I think of the claim that IBM made when it >introduced FORTRAN; "Programming is obsolete". These where the _same_ >claims made by the Ada advocates. None of this should be interpreted >as meaning that I think that the DC development and NASP research >should be halted - I'm just trying to inject what I see as healthy >skepticism into an otherwise euphoric discussion... A very good point, which I've mentioned once or twice. One of the greatest hardships faced by a new design is when it actually has to be designed and built - before that, it can be perfect. I consider DCX well worth building, to find out what those problems will be - maybe they can be fixed. I just hope they don't crash it on the very first flight - that tends to make Congress, investors, and the public overreact. For instance, I don't know whether the Titanic design was ever reused, though it was basically a good idea - it just had an idiot for a captain. And there doesn't seem to be much work going on these days on hybrid rockets, after Amroc's first launch burned up. I also consider the SSF problems to be encouraging - it means the designers are actually thinking about them. If fixes can be developed for the known problems, they might wind up with something that will actually work. >Several people have pointed that out, and thanks to all. But what >about DC-Y? The thermal protection system is a key system component, >which apparently hasn't progressed beyond the "then a miracle >happens.." stage. I'm not saying that the design should be frozen >(early design freezes have bought NASA a lot of headaches), but it >should at least be "slushy" before anyone starts broadcasing >projections on operating costs or turnaround times. That's the main problem - we get all these posts on sci.space describing how the DC-1 will cost $10,427,003 dollars per launch, have a payload of 20,328 pounds, and a 4.57-day turnaround time, usually expressed as though they were accomplished facts. >And now for something constructive, perhaps to be answered by someone >who knows Hunter personally: Has anyone involved with this project >made a thorough and methodical study of NASA's maintenance and >logistics records for the Shuttle fleet? There's ten years of data >there that _might_ be able to point up components, design elements, or >manufacturing techniques that should be avoided (or adopted) in the >next generation. There are certainly records on how many man-hours were spent servicing the various systems. There are also many records on how marginal those systems were in their performance on each flight. >Nonetheless, I'd hate to see the Shuttle become the Viet Nam of space >exploration - everyone too embarassed by the defeat to listen to the >lessons learned by the soldiers. There were certainly many things learned in Vietnam that were used in the next major conflict. Similarly, in an ALS proposal I heard a few years ago, many of the shortcomings of the Shuttle were discussed, along with possible ways to get around them. >Lou Adornato | "If I'd known I was going to live this long, >Supercomputer Systems, Inc | I'd have taken better care of myself" John Roberts roberts@cmr.ncsl.nist.gov ------------------------------ End of Space-tech Digest #108 *******************