Subject: Space-tech Digest #107 Contents: catapulting Pegasus (1 msg) Price of LOX (4 msgs) Re: In opposition to air-breathing SSTO (3 msgs) Re: Delta Clipper performance claims (3 msgs) DCX (6 msgs) short summary of Phoenix/DC-X history from Gary Hudson (1 msg) ------------------------------------------------------------ Date: Thu, 19 Mar 92 15:50 PST From: trost@reed.edu (Bill Trost) To: space-tech@cs.cmu.edu Subject: catapulting Pegasus (was: Ground launch systems (was Re: SDIO's SSTO (eieio) and NASP)) This thread just gave me a warped notion -- putting Pegasus on a steam-powered catapult on a tall mountain instead of dropping it from an airplane. Well, at least the debris field would be small.... :-) ------------------------------ From: henry@zoo.toronto.edu Date: Wed, 18 Mar 92 16:38:17 EST Subject: Re: Price of LOX To: space-tech@cs.cmu.edu >... LN2 has a lower boiling point than LOX, so it can be obtained >by simply letting the O2 boil out of liquid air. Hmmm ... Other way round: the LN2 boils off first. (Also, LN2 left exposed to air will turn into liquid air by condensing LOX, which is one reason not to leave it exposed to air.) I suspect the difference in prices is mostly wholesale vs. retail. You can bet that the launcher people get wholesale prices. Henry Spencer at U of Toronto Zoology henry@zoo.toronto.edu utzoo!henry ------------------------------ From: more%alcor.usc.edu@usc.edu (Max More) Subject: Re: Price of LN2 To: space-tech@cs.cmu.edu Date: Wed, 18 Mar 92 14:04:24 PST > One thing I vaguely remember: isn't that "$/ltr_LN2 ~ $/ltr_milk" figure > for *small lots* of LN2 in 50-ltr dewers? Maybe it's a *LOT* cheaper in > bulk ... ;-) > > Gordon D. Pusch > From my experience with cryonics suspension organizations, I can tell you that liquid nitrogen costs about $0.25 per liter in relatively small quantities (i.e., in the range of tens of liters per day). Max More ------------------------------ Date: Wed, 18 Mar 1992 18:17 EST From: "GORDON D. PUSCH" Subject: Re: Price of LOX --- Ooops!!! To: space-tech@cs.cmu.edu >From: henry@zoo.toronto.edu > > > ... LN2 has a lower boiling point than LOX, so it can be obtained > > by simply letting the O2 boil out of liquid air. Hmmm ... > > Other way round: the LN2 boils off first. (Also, LN2 left exposed > to air will turn into liquid air by condensing LOX, which is one reason > not to leave it exposed to air.) > Ooops!!! Sorry about that, Henry ... I got confused because I remembered that *ozone* froze above LN2 boiling temp.; remember about 2yrs ago when I suggested that slurried O3 in LN2 might make an, ummm, *interesting* oxidizer? ;-) Gordon D. Pusch ------------------------------ Date: Wed, 18 Mar 92 20:04:31 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: Hydrogen >I suspect the difference in prices is mostly wholesale vs. retail. >You can bet that the launcher people get wholesale prices. > > Henry Spencer at U of Toronto Zoology What does KSC do with the hydrogen it pumps out when a Shuttle launch is scrubbed? John Roberts roberts@cmr.ncsl.nist.gov ------------------------------ Date: Wed, 18 Mar 1992 16:59 EST From: "GORDON D. PUSCH" Subject: Re: In opposition to air-breathing SSTO To: space-tech@cs.cmu.edu > From: "Louis F. Adornato" > >> IMHO, the NASP/NDV uncertainties are likely to be *MUCH* larger than >> the DC-#'s; NASP is based on "numerical wind-tunnel" (i.e., computer) >> calculations, and, well ... GIGO. Hypersonic aero-thermo-chemo-dynamics >> in the NASP flight-regime is highly non-equilibrium, and rather poorly >> understood, because (as of 2 years ago) the relevent reaction-rates had >> *NOT YET BEEN MEASURED*. > > The accuracy of numerical aerodynamic simulation (NAS) has improved > greatly over the past few years. I understand that Ames ran a > comparison between the same body in thier supersonic wind tunnel, the > NAS system, and flight hardware, and discovered that the wind tunnel > was actually _less_ accurate than the NAS due to the effects of the > tunnel walls. They're now using the NAS to validate the wind tunnel > results. - Disclaimer: I have all of this second hand. > That may very well be true for a *SUPER*sonic wind-tunnel; but note that I was refering to the *HYPER*sonic regime. In hypersonic high-altitude regime where NASP/NDV will fly, there will be significant dissociation of air molecules (the *UNKNOWN* reaction-rates I refered to); furthermore, NASP/NDV will fly on the borderline between fluid and molecular flow, so that the usual approximations break down. Hence my comment about GIGO: I don't believe anyone's *hypersonic* flow-model is good enough to predict NASP/NDV performance. Note also that no one knows how to build a hypersonic windtunnel capable of simulating NASP/NDV flight-conditions; that's one of the reasons why the only way to test the NASP's SCRAMjets is to build a NASP ... > From: davidsen@crdos1.crd.ge.com > >> Furthermore (as Max Hunter points out) you're going to all this expense >> and effort to get ``free'' oxygen from the air --- when LOX retails for >> $0.05/lb! You're likely to spend far more on LH2 (at $1.50/lb) lugging >> the excess mass and drag of your jets than you'll ``save'' !!! > > Well, I don't think that's a fair statement. The oxygen is 'free' in > the sense that you don't have to lift it, not that you worry about the > dollar cost. > But Hunter *IS* talking about dollar cost!!! His claim is that even though the NASP will have a lower propellant *mass* than SSX, its propellant *cost* is *four times higher*! (Recall that his goal is to achieve an operating cost for SSX of about three time propellant cost.) But to address your point: you don't have to *lift* it, but you *DO* have to accelerate and compress it in your inlet [and turbocompressor]. The engines add drag; also, the inlets [and compresors] do work against an adverse pressure-gradient, so there are irreversible compression losses; both cost you fuel. You'll also have to *lift* an engine that masses 10--100 times as much, which costs you fuel *and* payload. So ``free'' oxygen actually has a real dollar cost. I see no logic in spending expensive LH2 to save cheap LOX ... Gordon D. Pusch ------------------------------ Date: Wed, 18 Mar 92 20:02:49 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: Airbreathing SSTO >From: "GORDON D. PUSCH" > >Note also that no one knows how to build a hypersonic windtunnel capable >of simulating NASP/NDV flight-conditions; that's one of the reasons why >the only way to test the NASP's SCRAMjets is to build a NASP ... Or to mount one on a rocket (or SR-71 for lower-speed tests). >> Well, I don't think that's a fair statement. The oxygen is 'free' in >> the sense that you don't have to lift it, not that you worry about the >> dollar cost. >> >But Hunter *IS* talking about dollar cost!!! His claim is that even though >the NASP will have a lower propellant *mass* than SSX, its propellant *cost* >is *four times higher*! (Recall that his goal is to achieve an operating >cost for SSX of about three time propellant cost.) For the time being, I'd be happy to get into a price range where cryogenic fuel *is* a significant part of the cost. Plenty of time to fine-tune it later... >But to address your point: >you don't have to *lift* it, but you *DO* have to accelerate and compress >it in your inlet [and turbocompressor]. To paraphrase Johnny Hart: SCRAMjets got turbocompressors??? John Roberts roberts@cmr.ncsl.nist.gov ------------------------------ Date: Wed, 18 Mar 1992 21:05 EST From: "GORDON D. PUSCH" Subject: Re: Air-breathing SSTO To: space-tech@cs.cmu.edu X-VMS-To: SPACE-TECH X-VMS-Cc: PUSCHG > From: John Roberts > >> Note also that no one knows how to build a hypersonic windtunnel capable >> of simulating NASP/NDV flight-conditions; that's one of the reasons why >> the only way to test the NASP's SCRAMjets is to build a NASP ... > > Or to mount one on a rocket (or SR-71 for lower-speed tests). > Rocket *maybe*, SR-71 *NO WAY*. The SR-71 can't reach the Mach 6--25 range relevent to the NASP's SCRAMjets operating conditions. BTW, last I heard, one of the open questions regarding the NASP was how to jump the gap between Mach 3 (where SR-71-type turboramjets wimp out), and Mach 6 (where the SCRAMjets cut in). Anybody know anything about this? Do the NASP people now think ordinary ramjets can jump the gap? >> But to address your point: >> you don't have to *lift* it, but you *DO* have to accelerate and compress >> it in your inlet [and turbocompressor]. > > To paraphrase Johnny Hart: SCRAMjets got turbocompressors??? > Note the square brackets, denoting an "optional" argument :-). I'm ragging on the *whole range* of air-breathing propulsion for SSTO, not just the NASP. Actually, I think that the *ONLY* range over which air-breathing and/or augmentation makes *any* sense is Mach 0--3+, where it's Isp is 1000--2000 secs. At Mach 3, the Isp of a jet is only about 2--3 times that of a rocket, and drops toward a rocket's asymptotically. The *HELLISH* aerothermal conditions it will have to endure above Mach 3 to get this small benifit just don't seem worth it to me. Gordon D. Pusch ------------------------------ Date: Thu, 19 Mar 92 10:56:38 CST From: ssi!lfa@uunet.UU.NET (Louis F. Adornato) To: uunet!cs.cmu.edu!space-tech@uunet.UU.NET Subject: Re: Delta Clipper performance claims > >...that's an awful lot of unknowns. My original > >objection stands. The first few hundred flights should have _no_ > >capability of fragging civilians. > > Certainly, but what has this to do with operational use? If DC is to > be certified to airliner standards, it will probably stack up that many > flights during development, testing, and certification. Only in the > missile business is something "fully operational" after four flights. Oy. My original comment was in response to the idea that, if the DC came in at slightly underpower for orbital flight, the first few flights could be _made_ orbital by building a rocket sled up the side of a mountain. I replied that there's no mountains in acceptable areas due to debris footprints intersecting populations. My objections where limited to a) using a launch site that would overfly civilians on the first few flights of the DC (george is assuming that after that the weight scrub will get the DC into orbital configuration), and b) siting any active launch system somewhere where it can't be tested without putting cities at risk, and c) siting said system so far north that you get a limited utility due to the large minimum inclination. You bring up another interesting point, though - how close is the shuttle to the number of flight hours generally needed to certify a commercial airplane? Lou Adornato | "Sure, the cow may have jumped over the Supercomputer Systems, Inc | moon, but she burned up on reentry" 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: Thu, 19 Mar 92 13:39:48 EST To: space-tech@cs.cmu.edu Subject: Re: Delta Clipper performance claims >You bring up another interesting point, though - how close is the shuttle >to the number of flight hours generally needed to certify a commercial >airplane? Flight hours are not, I think, very significant for this purpose. It's what you do with the flight hours. Almost all of the shuttle's flight hours are built up in free fall in a fairly benign environment; they are relevant to certifying things like life support but not to propulsion and flying qualities. The fact that it's only made 40-odd takeoffs and landings would, I'd think, be much more significant. Other strikes against it would be the lack of variation in takeoff/landing conditions, the fact that major abort modes have never been tested (airliners have to demonstrate severe worst-case aborted takeoffs, for example -- the brakes typically glow orange-hot at the end of that test), and the several near failures that have occurred. I also doubt that the FCC would certify any glider for airliner operations, especially one that is as difficult to fly as the shuttle orbiter. (To slow your descent you pull the nose up, right? Wrong! Pulling the nose up makes you drop *faster*!) Henry Spencer at U of Toronto Zoology henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: Thu, 19 Mar 92 13:03:11 -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: Delta Clipper performance claims >My original comment was in response to the idea that, if the DC came in >at slightly underpower for orbital flight, the first few flights could be >_made_ orbital by building a rocket sled up the side of a mountain. I didn't say the first flights, I said the first *vehicles.* Obviously, you could and should conduct a lot of suborbital flight tests before you try something like that. >You bring up another interesting point, though - how close is the shuttle >to the number of flight hours generally needed to certify a commercial >airplane? That depends on whether you're considering flight hours on the airframe or the propulsion system. A typical Shuttle flight lasts much longer than a typical airplance flight, but the powered phase is much shorter. Of course, launch and reentry are the most critical flight phases. ------------------------------ Date: Wed, 18 Mar 92 16:21 GMT From: CSG0669@vax2.queens-belfast.ac.uk To: space-tech@cs.cmu.edu Subject: DCX Sender: mnr@DAISY.LEARNING.CS.CMU.EDU Marc commented that Max did not have any direct connection with PALS. I don't know if it was formal, but the two had a long standing personal connection. Max once told me "Gary is the only person doing it right", ie meaning the Phoenix E. Max was for a time working with the people at Society Expeditions when they decided to part from PALS and considered doing it themselves. Yes, Gary & co were the prime movers on Phoenix E, but I've a strong feeling Max had a hand in it at an early date. You really have to understand how small our "fraternity" really is. We all know each other. And as to all the winged ideas: as I said in Space Digest. Max is NOT building an LEO shuttle. Wings are for shuttles. Wings are tied to planet Terra. You do not put wings on refuellable space ships. You do not use wings to land on the moon. I *DARE* anyone to bring the NASP in dead stick to Luna City :-) Dale Amon ------------------------------ Reply-To: davidsen@crdos1.crd.ge.com Date: Fri, 20 Mar 92 09:36:20 EST From: davidsen@crdos1.crd.ge.com To: space-tech@cs.cmu.edu Subject: Re: DCX Sender: mnr@DAISY.LEARNING.CS.CMU.EDU > And as to all the winged ideas: as I said in Space Digest. Max is NOT > building an LEO shuttle. Wings are for shuttles. Wings are tied to planet > Terra. You do not put wings on refuellable space ships. You do not use wings > to land on the moon. I *DARE* anyone to bring the NASP in dead stick to > Luna City :-) NASP is a special case: it has been flying in an atmosphere of political hot air for years, and is equiped for the aerodynamics of the environment. It uses steering committees for control... ------------------------------ Date: Thu, 19 Mar 92 15:38:07 CST From: ssi!lfa@uunet.UU.NET (Louis F. Adornato) To: uunet!cs.cmu.edu!space-tech@uunet.UU.NET Subject: Re: DCX > From Dale Amon: > > And as to all the winged ideas: as I said in Space Digest. Max is NOT > building an LEO shuttle. Wings are for shuttles. Wings are tied to planet > Terra. You do not put wings on refuellable space ships. You do not use wings > to land on the moon. I *DARE* anyone to bring the NASP in dead stick to > Luna City :-) Yeah, but I dare anyone to land a LEM in Leone. Building a cheap, reliable (as if they aren't the same thing in the long run...) LEO shuttle would certainly be a noble enough goal. Wouldn't something that's robust enough to make the trip from dirt to LEO be overbuilt for translunar or transmartian operations? It doesn't make a lot of sense to waste fuel on hauling reenty protection and a 2 or 3 g rated airframe from LEO to Luna. Why waste energy keeping your hydraulics from freezing up when you don't need them but an hour or so out of the whole trip? Anyway, this brings up some questions I've been dying to ask. I hate to display my ignorance, but I generally allow myself three stupid questions per day: 1) What sort of reentry attitude is planned for the DCX/Y? I don't see how it can be presenting the same surface that houses the engine bells (and then go back up without some MAJOR engine rework), so that must mean it's comming in presenting the same surface that it presented in ascent. But I don't see how you could sheild that much surface area. I guess it might have an asymetric design, and come in "horizontally", but that means some really weird control problems during ascent. 2) What type of heat protection is planned? I think we're all agreed that shuttle type tiles aren't ready for use on a vehicle with a planned turnaround time of a few weeks. On the other hand, an ablative large enough is going to cause some real operating costs and boost turnaround time. What's left? 3) How's this thing going to land? I got the impression from "Falling Angels" and from the article in "Discover" (ok, I thumbed through, I'm not proud of it, but I didn't look at the pictures. Much.) that it's going to come down BEF and engines hot, like a lunar lander. It seems to me that this is going to result in a *lot* of extra fuel being hauled up, with perfectly good air available to act as a braking agent. Modern square parachutes are highly controllable and yield amazingly low landing shock, probably lower than the ascent load. And they're a lot lighter than either wings or fuel. I can't see that chute repacking is going to boost the operational costs *that* much. Lou Adornato | "Sure, the cow may have jumped over the Supercomputer Systems, Inc | moon, but she burned up on reentry" 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: Fri, 20 Mar 92 17:46:16 -0600 From: ewright@bach.convex.com (Edward V. Wright) To: space-tech@cs.cmu.edu Subject: Re: DCX >Wouldn't something >that's robust enough to make the trip from dirt to LEO be overbuilt for >translunar or transmartian operations? It doesn't make a lot of sense >to waste fuel on hauling reenty protection and a 2 or 3 g rated >airframe from LEO to Luna. Not necessarily. If you wanted to keep a Delta Clipper in space all the time, basing it in orbit or on the Moon, you could strip off the thermal protection. But it's going to be awhile before Luna City has the sort of facilities a spaceship requires for periodic overhaul. Until then it's a handy thing for your LEM to be able to return to Earth anyhow. >1) What sort of reentry attitude is planned for the DCX/Y? Nose-first, high-angle-of-attack reentry, like an ICBM warhead. Base- first, like the Apollo CM was considered also. I believe this was chosen to give better cross-range. >I don't see >how it can be presenting the same surface that houses the engine bells >(and then go back up without some MAJOR engine rework) That would work also, but if you use bell nozzles (instead of an aerospike/ plug nozzle) you would need to cool the nozzles by dumping some LH2. But as I said, Delta Clipper isn't doing it that way. >2) What type of heat protection is planned? There are several options, including transpirational (water) cooling. I haven't heard which one the DC project picked -- if they've even decided yet. Thermal protection is much less of a problem than it was with the Shuttle because the vehicle's a lot lighter. >3) How's this thing going to land? It seems >to me that this is going to result in a *lot* of extra fuel Not really. Since the propellent tanks are almost empty at touchdown, the vehicle is pretty light. Atmospheric drag actually does most of the breaking, slowing the vehicle to a terminal velocity of ~200 mph. The vehicle only needs to light up a few of its engines for several seconds to make the final approach. I doubt a parachute would be any lighter. ------------------------------ Date: Fri, 20 Mar 92 17:50:46 -0600 From: pgf@nasa14.usl.edu (Phil G. Fraering) To: space-tech@cs.cmu.edu, ssi!lfa@uunet.uu.net Subject: Re: DCX Well, DC-X is supposed to come in sorta sideways, nose up, which I think answers most of your question... Phil ------------------------------ From: henry@zoo.toronto.edu Date: Sat, 21 Mar 92 19:43:56 EST To: space-tech@cs.cmu.edu Subject: Re: DCX >... Wouldn't something >that's robust enough to make the trip from dirt to LEO be overbuilt for >translunar or transmartian operations? It doesn't make a lot of sense >to waste fuel on hauling reenty protection and a 2 or 3 g rated >airframe from LEO to Luna... It definitely does not make a lot of sense, *if* you ignore development costs. Fact is, if you've already got something that *can* make the trip, it can make a lot of sense to use it, even if you could develop something better after several years' work and several billion dollars. I don't think anyone is going to badly compromise DC-1 as a LEO shuttle just for the sake of lunar capability. However, if it turns out, as forecast, that DC-1 has quite a bit of margin under its belt as a LEO craft, then the incremental cost of adding lunar capability is probably quite minor, given on-orbit refuelling (which is not entirely trivial for cryogenic fluids). >1) What sort of reentry attitude is planned for the DCX/Y? Forward, nose-high; it's a hypersonic lifting body. >I don't see >how it can be presenting the same surface that houses the engine bells >(and then go back up without some MAJOR engine rework)... This isn't done, but is actually no big trick. If you blow a little bit of gas out through the engine at low velocity, it keeps the shock wave and the accompanying high temperatures at bay. Some aerospike concepts cool the rest of the base with a small flow of liquid hydrogen and then exhaust it through the chambers. There have also been designs for things like high-orbit OTVs that actually ran the engine at low thrust during base-forward aerobraking. Henry Spencer at U of Toronto Zoology henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: Thu, 19 Mar 92 17:49 PST From: jean@katie.dgi.com (Jean Kim) To: space-tech@cs.cmu.edu Subject: short summary of Phoenix/DC-X from Gary Hudson Since a lot of you were speculating about Phoenix/DC-X, I asked Gary if he would be interested in explaining a few things. He said he is extremely busy at the moment but will give more detailed summary as soon as things quiet down. Mr. Amon, you are absolutely right about the "fraternity" bit. small world, this circle of people. :) Here is his short response. More to come later .... -jeanie *===================================* * jean@dgi.com * * My supervisor thinks I'm working! * *===================================* -------------------Begin Forwarded Message----------------------- My short reponse is that the Phoenix E.(and all previous and post Phoenix vehicles) was designed by me and Tom Broaz, alone. I convinced Max Hunter to join me in promoting the Phoenix to investors and (in 1985) to Society Expeditions, and he actually had a business card which named him as Senior VP of PacAm. Max was involved with PacAm from about 1983 to 1988. During this time, he was also employed by Lockheed. In 1987, with my approval, he conducted a study of the Phoenix (slightly redesigned, using RL10 engines) called X-OP (for X-operational). Lockheed almost bought off on the concept, but then Max retired in 1988 and he renamed the concept SSX (for SpaceShip eXperimental). At a Citizen's Council on National Space Policy meeting chaired by Jerry Pournelle in December of '88, Max and I sold the attendees on the basic idea, and it was presented to the Vice-President by Max, Jerry, and Gen. Dan Graham of High Frontier Inc. in February '89. An Aerospace Corporation study in July of that year confirmed that the design would work. Contracts were then issued to four companies (MDAC, General Dynamics, Boeing, and Rockwell) in August of 1990, leading to the award of Phase II ($52 million) to MDAC last yeat to build a DC-X demonstrator. Unfortunately, while I had consulted to Boeing and GD, I was not invited to work on the MDAC project. There, the matter stands for me. Gary C. Hudson ------------------------------ End of Space-tech Digest #107 *******************