Quote from: Lobo on 04/13/2015 06:27 pm Unsure about the cause of the one that destroyed the pad (but I think that was the one where one engine shutdown right after liftoff, and so the computer shut the opposite engines down as they didnt' gimbal, and it lost thrust and fell back to the pad). From what I remember, but I don't have a source that one blew up before launch during fueling, killing many people who were near the pad. I may be confusing it with another accident.
Unsure about the cause of the one that destroyed the pad (but I think that was the one where one engine shutdown right after liftoff, and so the computer shut the opposite engines down as they didnt' gimbal, and it lost thrust and fell back to the pad).
Just before liftoff, the LOX turbopump in the #8 engine exploded (the pump was recovered from the debris and found to have signs of fire and melting), the shock wave severing surrounding propellant lines and starting a fire from leaking fuel. The fire damaged various components in the thrust section[41] leading to engine shutdown. The KORD computer intentionally shut off the opposing #7 and #19 engines after detecting abnormal pressure and turbopump speeds. Telemetry did not provide any explanation as to what shut off the other engines. Engine #18, which had caused the booster to lean over 45 degrees, continued operating until impact, something engineers were never able to satisfactorily explain. It could not be determined exactly why the #8 turbopump had exploded. Working theories were that either a piece of a pressure sensor had broken off and lodged in the pump, or that its impeller blades had rubbed against the metal casing, creating a friction spark that ignited the LOX.After the accident, Vladimir Barmin, who was in overall charge of the launch facilities at Baikonour, demanded that a feature be installed in the KORD computer to prevent the engines from being cut off until at least 50 seconds into launch to prevent the vehicle from coming down on or around the pad again. [42] [43] The destroyed complex was photographed by American satellites, disclosing that the Soviet Union was building a Moon rocket.[37] The rescue system saved the spacecraft again. After this flight, fuel filters were installed in later models.[37] It also took 18 months to rebuild the launch pad and delayed launches. This was one of the largest artificial non-nuclear explosions in human history and was visible that evening 22 miles (35 kilometres) away at Leninsk (See Tyuratam).[44]]
Quote from: Robotbeat on 04/13/2015 03:06 amIt's quite likely the Soviets simply couldn't afford a test stand to do these sorts of tests on (plus they were single-use, although they did do batch testing), but it meant the end of the program.As I understood, it wasn't so much that they -couldn't- have built a stand for the N-1 1st stage (or maybe it was), but that that wasn't really that big of a deal to the Soviets. Their methodology was to launch, and if it failed, analyzed the reason, fix it, and launch again. Wash, rinse, repeat until successful. I'd read somewhere that they'd planned 7 test launches to work out the issues. That was normal for Soviet development and any failures were kept secret per Soviet poltics. Only successes were let be known.Politics, rather than engineering then killed off N-1 after we beat them to the moon.Were the first D4 and AV boosters fully tested prior to their first flights?
It's quite likely the Soviets simply couldn't afford a test stand to do these sorts of tests on (plus they were single-use, although they did do batch testing), but it meant the end of the program.
Quote from: baldusi on 04/10/2015 06:58 pmQuote from: Lobo on 04/10/2015 05:40 pmQuote from: Semmel on 04/10/2015 04:48 pmIf you read musks quote carefully (the one stated 2 pages back) he neverer said that raptor changed in thrust, he simply stated where th. T/W optimum is. He just evaded to answer that question...Yea, but I think that's a bit of a reach. He was asked about an "official" power of Raptor at 1.5Mlbf, and responded that it looks like the optimum looks to be around 500klbs. Yes, it's possible he said that without meaning anything by it, but that would be fairly intentionally deceitful. Why? That doesn't realy seem like his style. Vague, yes. But deliberately deceitful?I don't think he brings it up if there wasn't a reason for it...IMHO. Please bear in mind that the cost of developing a rocket engine is roughly proportional to the thrust squared. Thus, a 500klbf Raptor could be as much as 10 times cheaper than a 1.6Mlbf one.And as the first iteration in the Raptor brand, would make sense for 2018. considering cash flow between then and now! Then further iterations would benefit from the added cash flow of the first Raptor and SpaceX projects over the following 15 years my half pound worth (inflation folks ) Gramps
Quote from: Lobo on 04/10/2015 05:40 pmQuote from: Semmel on 04/10/2015 04:48 pmIf you read musks quote carefully (the one stated 2 pages back) he neverer said that raptor changed in thrust, he simply stated where th. T/W optimum is. He just evaded to answer that question...Yea, but I think that's a bit of a reach. He was asked about an "official" power of Raptor at 1.5Mlbf, and responded that it looks like the optimum looks to be around 500klbs. Yes, it's possible he said that without meaning anything by it, but that would be fairly intentionally deceitful. Why? That doesn't realy seem like his style. Vague, yes. But deliberately deceitful?I don't think he brings it up if there wasn't a reason for it...IMHO. Please bear in mind that the cost of developing a rocket engine is roughly proportional to the thrust squared. Thus, a 500klbf Raptor could be as much as 10 times cheaper than a 1.6Mlbf one.
Quote from: Semmel on 04/10/2015 04:48 pmIf you read musks quote carefully (the one stated 2 pages back) he neverer said that raptor changed in thrust, he simply stated where th. T/W optimum is. He just evaded to answer that question...Yea, but I think that's a bit of a reach. He was asked about an "official" power of Raptor at 1.5Mlbf, and responded that it looks like the optimum looks to be around 500klbs. Yes, it's possible he said that without meaning anything by it, but that would be fairly intentionally deceitful. Why? That doesn't realy seem like his style. Vague, yes. But deliberately deceitful?I don't think he brings it up if there wasn't a reason for it...IMHO.
If you read musks quote carefully (the one stated 2 pages back) he neverer said that raptor changed in thrust, he simply stated where th. T/W optimum is. He just evaded to answer that question...
Emily Shanklin indicated in late 2013 that the Raptor would be the first of a "family of engines" designed for the exploration and colonization of Mars. Could you elaborate on her wording, i.e. was she simply referring to a vacuum version and standard version, or do you plan on building multiple methane-based engines with significantly different thrust and size specifications?[–]ElonMuskOfficialDefault plan is to have a sea level and vacuum version of Raptor, much like Merlin. Since the booster and spaceship will both have multiple engines, we don't have to have fundamentally different designs. This plan might change.
Thrust to weight is optimizing for a surprisingly low thrust level, even when accounting for the added mass of plumbing and structure for many engines. Looks like a little over 230 metric tons (~500 klbf) of thrust per engine, but we will have a lot of them
Delta IV booster was fully test fired before its first flight (may not have been the same booster but instead a qualification booster). I don't know about Atlas V, but it was an evolution of the Atlas III (same basic engines).And really, both vehicles had extensive development history before launch. A better analogy if you're talking a new rocket would be early rockets like Saturn V which were not mere evolutionary steps of previous rockets.
Quote from: CyclerPilot on 04/11/2015 02:20 pmQuote from: MikeAtkinson on 04/10/2015 08:22 pmQuote from: Lobo on 04/10/2015 05:29 pmReally? I thought Elon and SpaceX typically talked about a 30% penalty for reuse, not a 100% penalty?I think a 130mt fully reusable LV might be more like a 185mt expendable? And a 120mt fully reusable LV like a 170mt expendable. Which would be larger than Saturn INT-21, but not too much so.I'd guess the booster would need around 15-19 Raptors to do that, with maybe 3 vacuum Raptors on the upper stage/MCT?Or am I really off there?Elon has said:15% barge landing, upper stage expendable.30% RTLS, upper stage expendable.50% RTLS with upper stage reuse.That is for Merlin 1D, Raptor will probably do a bit better because of its higher Isp.If the MCT IS the upper stage, then there is no penalty for upper stage reuse (already need legs, TPS, landing thrusters to land on Mars, and Earth landing propellant comes from Mars). This should make it possible to launch the MCT full of cargo. Granted, most flights will be refueling flights, so there will be an upper stage reuse penalty for those.Yes, if you look up thread this is exactly what I was saying.
Quote from: MikeAtkinson on 04/10/2015 08:22 pmQuote from: Lobo on 04/10/2015 05:29 pmReally? I thought Elon and SpaceX typically talked about a 30% penalty for reuse, not a 100% penalty?I think a 130mt fully reusable LV might be more like a 185mt expendable? And a 120mt fully reusable LV like a 170mt expendable. Which would be larger than Saturn INT-21, but not too much so.I'd guess the booster would need around 15-19 Raptors to do that, with maybe 3 vacuum Raptors on the upper stage/MCT?Or am I really off there?Elon has said:15% barge landing, upper stage expendable.30% RTLS, upper stage expendable.50% RTLS with upper stage reuse.That is for Merlin 1D, Raptor will probably do a bit better because of its higher Isp.If the MCT IS the upper stage, then there is no penalty for upper stage reuse (already need legs, TPS, landing thrusters to land on Mars, and Earth landing propellant comes from Mars). This should make it possible to launch the MCT full of cargo. Granted, most flights will be refueling flights, so there will be an upper stage reuse penalty for those.
Quote from: Lobo on 04/10/2015 05:29 pmReally? I thought Elon and SpaceX typically talked about a 30% penalty for reuse, not a 100% penalty?I think a 130mt fully reusable LV might be more like a 185mt expendable? And a 120mt fully reusable LV like a 170mt expendable. Which would be larger than Saturn INT-21, but not too much so.I'd guess the booster would need around 15-19 Raptors to do that, with maybe 3 vacuum Raptors on the upper stage/MCT?Or am I really off there?Elon has said:15% barge landing, upper stage expendable.30% RTLS, upper stage expendable.50% RTLS with upper stage reuse.That is for Merlin 1D, Raptor will probably do a bit better because of its higher Isp.
Really? I thought Elon and SpaceX typically talked about a 30% penalty for reuse, not a 100% penalty?I think a 130mt fully reusable LV might be more like a 185mt expendable? And a 120mt fully reusable LV like a 170mt expendable. Which would be larger than Saturn INT-21, but not too much so.I'd guess the booster would need around 15-19 Raptors to do that, with maybe 3 vacuum Raptors on the upper stage/MCT?Or am I really off there?
In your recent MIT talk, you mentioned that you didn't think 2nd stage recovery was possible for the Falcon 9. This is due to low fuel efficiency of kerosene fuel, and the high velocities needed for many payloads (high orbits like Geostationary orbit). However, you also said that full reusability would be possible for the Mars Colonial Transporter launch vehicle.What have you learned from flights of Falcon 9 that taught youa) that reuse of its second stage won't be possible and b) what you'll need to do differently with MCT to reuse its second stage.[–]ElonMuskOfficial:Actually, we could make the 2nd stage of Falcon reusable and still have significant payload on Falcon Heavy, but I think our engineering resources are better spent moving on to the Mars system.MCT will have meaningfully higher specific impulse engines: 380 vs 345 vac Isp. For those unfamiliar, in the rocket world, that is a super gigantic difference for stages of roughly equivalent mass ratio (mass full to mass empty).
[–]ElonMuskOfficial:Actually, we could make the 2nd stage of Falcon reusable and still have significant payload on Falcon Heavy, but I think our engineering resources are better spent moving on to the Mars system.MCT will have meaningfully higher specific impulse engines: 380 vs 345 vac Isp. For those unfamiliar, in the rocket world, that is a super gigantic difference for stages of roughly equivalent mass ratio (mass full to mass empty).
[–]ElonMuskOfficialDefault plan is to have a sea level and vacuum version of Raptor, much like Merlin. Since the booster and spaceship will both have multiple engines, we don't have to have fundamentally different designs. This plan might change.
MCT is planned to be pretty darned light, if it would have a roughly equivalent mass ratio to a reusable F9US, which wouldn't have any systems or hardware associated with a crew as MCT will. Hard to say how light that is, but if it's roughly the size of the S-II stage, which was 45mt dry, then ~60mt isn't an unreasonable guestimate at the spacecraft's dry mass, which has been thrown around here some. (Although it's still only a guestimate).
Quote from: Lobo on 04/13/2015 08:48 pmMCT is planned to be pretty darned light, if it would have a roughly equivalent mass ratio to a reusable F9US, which wouldn't have any systems or hardware associated with a crew as MCT will. Hard to say how light that is, but if it's roughly the size of the S-II stage, which was 45mt dry, then ~60mt isn't an unreasonable guestimate at the spacecraft's dry mass, which has been thrown around here some. (Although it's still only a guestimate).If we are right about the MCT being the spacecraft which is its own upper stage then one way of thinking about it is as having components:1. Stage - tanks, main engine, TVC, landing legs, etc.2. Fairing - structure to contain the payload, payload adapter, heat shield.3. Long duration - solar panels, radiators, long range comms, cryocooler, etc. (possibly including SEL course correction).4. Payload - hab or cargo.I think it difficult to get all of the MCT components (not including payload - obviously) into 60 tonnes. I have yet to see a good bottom-up estimate of the MCT dry mass.
When considering my Saturn S-II stage analog. If it was in LEO, fully fueled, how much could it get through TMI?
...On a note. If Elon Musk want's 15 million lbs thrust to get 100 tons to Mars, I still wonder why 12 million can't get 80 tons and he can use Kennedy and not have to build another launch facility. ...
Quote from: spacenut on 06/22/2015 05:39 pm...On a note. If Elon Musk want's 15 million lbs thrust to get 100 tons to Mars, I still wonder why 12 million can't get 80 tons and he can use Kennedy and not have to build another launch facility. ...I can think of at least two advantages to building a new launch facility: (Potentially) more control and fewer conflicts with the range and it reduces the impact to the flow of the existing launch manifest.After all, they're hoping that the launch market expands and that they get a big chunk of the business.
Is there any advantage in throttling down at take-off in LV performance to 12 mlbf and at appropriate altitude throttle up to 15 mlbf?I was thinking of range limitations of 12 mlbf that has been talked about a lot.
Quote from: symbios on 06/22/2015 08:45 pmIs there any advantage in throttling down at take-off in LV performance to 12 mlbf and at appropriate altitude throttle up to 15 mlbf?I was thinking of range limitations of 12 mlbf that has been talked about a lot.I see this brought up a lot, and the problem is that right at launch is exactly when you need the most thrust. If you can get your rocket off the ground with a 1.2 T/W ratio using 12 mlbf of thrust you'll actually get better performance by leaving off the extra engines it would take to reach 15 mlbf.
Quote from: Owlon on 06/22/2015 09:11 pmQuote from: symbios on 06/22/2015 08:45 pmIs there any advantage in throttling down at take-off in LV performance to 12 mlbf and at appropriate altitude throttle up to 15 mlbf?I was thinking of range limitations of 12 mlbf that has been talked about a lot.I see this brought up a lot, and the problem is that right at launch is exactly when you need the most thrust. If you can get your rocket off the ground with a 1.2 T/W ratio using 12 mlbf of thrust you'll actually get better performance by leaving off the extra engines it would take to reach 15 mlbf.Can the rocket tolerate an engine failure at liftoff commit with a 1.2 T/W? The rocket is only safer with multiple engines if it can tolerate an engine failure. This is most important at liftoff with a rocket as large as being discuss here as if you lose the rocket at takeoff you will lose a lot of infrastructure.