Quote from: Star One on 10/31/2017 11:55 amSpeculative. This isn’t the most complex of programs and is entirely doable within the timeframe given by a company like Boeing and their experience in these areas.Sure they do, so had Lockheed with the X33 and then we had Constellation and all the other "wonderful" projects of the past 30 years. All had cost and time overruns.The problem is that the timeframe falls right into the ballpark time where a new administration would cancel it. Has happened before. Personally, I am also underwhelmed by the concept, considering what SpaceX and Blue are doing right now. If this was an SSTO, it would be interesting but as it is, I am not at all excited.
Speculative. This isn’t the most complex of programs and is entirely doable within the timeframe given by a company like Boeing and their experience in these areas.
I think Darpa wants to use mach10 capability for highspeed testing of other vehicles eg scamjet missiles.Sent from my SM-T810 using Tapatalk
One of the drawbacks of the SpaceX and Blue concepts is the low staging velocity dictating a large and expensive upper stage.
If the system was optimized for such a small payload, I am pretty sure the staging velocity could be higher (and the upper stage smaller). IIRC, a F9 first stage by itself is almost SSTO capable. So they should be able to do a Mach 10 MECO quite easily with such a small load on top and still have enough fuel for RTLS. I would assume that they could even remove a few Merlins from the first stage, but I may be wrong with that.
Quote from: Elmar Moelzer on 11/01/2017 02:55 pmIf the system was optimized for such a small payload, I am pretty sure the staging velocity could be higher (and the upper stage smaller). IIRC, a F9 first stage by itself is almost SSTO capable. So they should be able to do a Mach 10 MECO quite easily with such a small load on top and still have enough fuel for RTLS. I would assume that they could even remove a few Merlins from the first stage, but I may be wrong with that.Quite possibly.The problem is not the going up. It's the coming down, as SX realized some years ago. You're looking at something like 10x the KE and PE per Kg of mass from LEO that you are from their staging velocities and altitudes. That's what's killed talk of a reusable F9 US.
Quote from: john smith 19 on 11/02/2017 10:01 amQuote from: Elmar Moelzer on 11/01/2017 02:55 pmIf the system was optimized for such a small payload, I am pretty sure the staging velocity could be higher (and the upper stage smaller). IIRC, a F9 first stage by itself is almost SSTO capable. So they should be able to do a Mach 10 MECO quite easily with such a small load on top and still have enough fuel for RTLS. I would assume that they could even remove a few Merlins from the first stage, but I may be wrong with that.Quite possibly.The problem is not the going up. It's the coming down, as SX realized some years ago. You're looking at something like 10x the KE and PE per Kg of mass from LEO that you are from their staging velocities and altitudes. That's what's killed talk of a reusable F9 US. Was not saying that they should/ could do SSTO with the first stage, but they could certainly do Mach 10 for staging maybe still do an RTLS with such a small payload and second stage on top of it.
I don't think it could. If you stage at 3,000 m/s, you need over 3,000 m/s just to null downrange velocity of the booster (while carrying entry and landing fuel). I get the F9 booster as having 3,300 m/s available at that point, which is not enough considering entry and landing need over 1,000 m/s. It's almost easier to just send the booster on into orbit than to RTLS from Mach 10.XS-1 gets around this by using the atmosphere to slow down, turn around, and glide back empty. This should work if it flies a depressed trajectory, just exiting the atmosphere long enough for the upper stage to get to orbit. With a fairly thrusty upper stage (e.g. 35 klbf Broadsword), this takes ~130 seconds, during which time the booster will coast ~390 km downrange. This can be less if the upper stage eats some of the gravity losses.
Quote from: Elmar Moelzer on 11/02/2017 05:39 pmWas not saying that they should/ could do SSTO with the first stage, but they could certainly do Mach 10 for staging maybe still do an RTLS with such a small payload and second stage on top of it.I don't think it could. If you stage at 3,000 m/s, you need over 3,000 m/s just to null downrange velocity of the booster (while carrying entry and landing fuel). I get the F9 booster as having 3,300 m/s available at that point, which is not enough considering entry and landing need over 1,000 m/s. It's almost easier to just send the booster on into orbit than to RTLS from Mach 10.
Was not saying that they should/ could do SSTO with the first stage, but they could certainly do Mach 10 for staging maybe still do an RTLS with such a small payload and second stage on top of it.
Quote from: envy887 on 11/02/2017 06:50 pmQuote from: Elmar Moelzer on 11/02/2017 05:39 pmWas not saying that they should/ could do SSTO with the first stage, but they could certainly do Mach 10 for staging maybe still do an RTLS with such a small payload and second stage on top of it.I don't think it could. If you stage at 3,000 m/s, you need over 3,000 m/s just to null downrange velocity of the booster (while carrying entry and landing fuel). I get the F9 booster as having 3,300 m/s available at that point, which is not enough considering entry and landing need over 1,000 m/s. It's almost easier to just send the booster on into orbit than to RTLS from Mach 10.The Falcon 9 1.1 first stage by itself has a DeltaV of at least 8300 m/s according to my calculations.Of course, then you need to add the weight of an upper stage plus its fuel. Let's assume some 20 tons of mass for that (dry weight of a conservative 3,000 kg plus the payload of 1,000 kg and the rest is fuel).With that I still get a Delta V of at least 7500 m/s and that is assuming it carries the fueled second stage all the way back too. So it would still have 1500 m/s for the rest. Things may be looking even better with the latest versions of Falcon 9 and even more with block 5.I might be wrong somewhere, but from this back of the envelope calculation, it still sounds plausible to me.
Quote from: Elmar Moelzer on 11/03/2017 02:36 amQuote from: envy887 on 11/02/2017 06:50 pmQuote from: Elmar Moelzer on 11/02/2017 05:39 pmWas not saying that they should/ could do SSTO with the first stage, but they could certainly do Mach 10 for staging maybe still do an RTLS with such a small payload and second stage on top of it.I don't think it could. If you stage at 3,000 m/s, you need over 3,000 m/s just to null downrange velocity of the booster (while carrying entry and landing fuel). I get the F9 booster as having 3,300 m/s available at that point, which is not enough considering entry and landing need over 1,000 m/s. It's almost easier to just send the booster on into orbit than to RTLS from Mach 10.The Falcon 9 1.1 first stage by itself has a DeltaV of at least 8300 m/s according to my calculations.Of course, then you need to add the weight of an upper stage plus its fuel. Let's assume some 20 tons of mass for that (dry weight of a conservative 3,000 kg plus the payload of 1,000 kg and the rest is fuel).With that I still get a Delta V of at least 7500 m/s and that is assuming it carries the fueled second stage all the way back too. So it would still have 1500 m/s for the rest. Things may be looking even better with the latest versions of Falcon 9 and even more with block 5.I might be wrong somewhere, but from this back of the envelope calculation, it still sounds plausible to me.You appear to be missing gravity and drag losses on the first stage, which take all of that 1500 m/s and maybe a little more.XS-1 is supposed to put 1,300 kg to SSO, so lets try to match that with F9 staging at 3,000 m/s. Orbital velocity is about 7750 m/s, and it gains nothing from rotation of the Earth, so the upper stage needs 4750 m/s. With a dry stage mass fraction of 10%, the upper stage, payload, and propellant are about 9 tonnes (varies slightly depending on the fuel choice, but not enough to matter here). The F9 v1.2 booster is 27 tonnes dry and holds 436 tonnes of kerolox, and with the 9 t upper stage total GLOM is 471 tonnes and mass at MECO (~4600 m/s with drag and grav losses) is 101 tonnes. Mass after separation is 92 tonnes, and after boostback (3350 m/s) is 34 tonnes. The 7 tonnes of remaining fuel are enough for about 1/2 of the entry burn, so this won't work, although we're pretty close.
XS-1 (now renamed XS-P for Experimental Spaceplane Program) program of the Defense Advanced Research Projects Agency (DARPA).
Quote from: russianhalo117 on 12/13/2017 04:32 amXS-1 (now renamed XS-P for Experimental Spaceplane Program) program of the Defense Advanced Research Projects Agency (DARPA).This seems to be the first time it's called XS-P rather than XS-1, which was the formal name of the vehicle that broke the sound barrier.http://spacenews.com/darpa-aims-to-disrupt-national-security-space-business/DARPA are saying this really is happening and hardware is going to actually get built. They are also saying if it does Boeing will decide if they want to develop it as a service that they can then sell back to the DoD and (presumably) other customers. This is very loosely the model of the X33 programme, which ended so badly. Time will tell if any lessons were learned or if (yet again) the USG has been played like "A banjo at an Ozark hoedown."
Is there any reason you are making this comparison at this early stage? It makes it look like you have a desire to put a negative spin on things. You yourself admit that the similarities are weak at best.
My read is that the program is being redirected unsubtlely. It provides a means for a response to certain threats, at a different scale than intended, and compromises on the economics of operation to get there.
You might be able to apply Shuttle related content to do this. But all the baggage comes along as well. Unlike Masten's approach, which I much preferred/recommended.
Boeing has immense reputation/skills/capability. The trouble they face is in choosing "what not to do", and "why not to do it".
Boeing were partnering with Blue NOT Masten who competiting for same contract. With Blue they had option of proven BE3 or maybe BE4. Why they choose RS25 over 5x BE3 we may never know, but RS25 has proved its self as reuseable engine on shuttle.
There is nothing wrong with VTOHL. Its a very low risk approach for Boeing who are experts at HL. May not scale but that doesn't matter for this LV.