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Kermann Nolandung

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Everything posted by Kermann Nolandung

  1. Ariane 5 used common bulkhead on its main stage. Ariane 5 and 6 are heavy-lift launchers, heavy because they were designed to be able to launch two payloads in GTO. But the today's market is looking for more versatile missions, Ariane 5 is usually too heavy for a single payload. Therefore in a redesign, the payload mass criteria can be loosened in an optimisation study. A64 lifts more mass than A5 but less than the abandonned A5 ME with the Vinci engine Separate tanks are easier, cheaper than a single tank with a common bulkhead, at the expense of higher dry mass. We can notice that the boosters are now attached to the intertank structure ; the LOX tank is no longer pulled but pushed by the boosters. For the second stage, I guess they repeat the same industrial process (it is the same contractor) ; that leaves room for optimisation in the event of futur need.
  2. On his comment about the steep ascent that reaches 470 km, this is not the usual profile at 200-250 km, but we can notice the flight is not at its usual inclinaison. For this part of flight I guess the launcher must keep communication with the ground. The video shows the coverage of the tracking stations. After Kourou, the next one is Santa Maria of the Azores 4500 km away. Coincidentally, the flight peaked at 470 km at mid distance and 470 km is the height above surface for a distance to horizon at 2500 km (a little more than half distance). This is most likely the constraint imposing the 470 km peak.
  3. Nautical mile and kilometre are both defined by the one minute of arc. One is defined in a sexagesimal system where a circle subdivided in 360° (degree), itself in 60’ (arcminute), itself in 60”(arcsecond). The other one is defined in a decimal system where a circle is subdivided into 400ᵍ (grad or gon), itself in 100 centigrad (centesimal minute of arc). 1 kilometre is the distance defined by one centesimal minute of arc of the Earth’s circumference (40 000 km). 1 nautical mile is the distance defined by one minute of arc of the Earth’s circumference (21 600 NM). milli- prefix is a subdivision in a decimal system. In a way 1 meter is 1 millikilometre To be consistent, a statute mile subdivision should be chosen among the furlong, chain, rod, yard, foot, etc.
  4. ESA is the intergovernmental space agency that coordinates the european space programmes. Eventually the budget, programmes and member participations are voted by the member states. In ESA there are mandatory programmes where each member state contributes an amount proportional to their gross national product and optional programmes. The launchers are optional programmes, the members are free to participate or not. It should be noted that ESA is not a sub-organization of the European Union but a different one. Alongside ESA, some members have their own national space agency (CNES, DLR, ASI…). Arianespace is the company in charge of providing launch service from Kourou spaceport. Its offer includes launch with Ariane, Vega and formerly Soyuz from Kourou. ArianeGroup is a joint venture of aerospace companies (with activities mainly in France and Germany) that was recently formed to develop and build Ariane 6 launcher. The share of the work of the prime and sub-contractors is then divided between the members in proportion to their participation. Vega is a launcher developed and manufactured by Italian agency and companies. The manufacturer is Avio. Last year, Italy and Avio negotiated that future Vega launches would no longer have to be marketed through Arianespace. That means it becomes a new competitor. With Ariane 6, unlike the previous generations, ESA has entrusted ArianeGroup, a private company, with the development of the rocket. This company is supposed to develop the launcher within a fixed budget and assume the risks. We can see where they are today. The company is calling for a budget increase and members complain about the extra costs. ArianeGroup seems easily to blame, but I guess nobody (ESA, members, ArianeGroup, contractors) is clean. One issue is that it has to follow the principle of geographical return. For example, ArianeGroup’s CEO has revealed that while he engaged cost reduction in his company, he faced dramatic increase in costs from subcontractors (some of whom, understandly, come from countries that complain about the cost of the programme). Who to blame ? If I were one of the CEO of one of the subcontractors, it would be my duty to make the most of it from a kind of a monopol situation. I don’t know the contractual details, but I can imagine a lot of reasons for the delays, extra costs and tense discussions.
  5. I'd really like to see a DLC that gives a realistic flavour to KSP2 and would include: - An intermediate scale solar system (x3?) at least for Kerbin and Mun. Reaching orbit on Kerbin should be far more demanding than a suborbital jump. - Patch-conic physics is all very well. But introducing a fictitious J2 effect (a fake Kerbin’s oblateness) on the low orbit would allow an orbit precession that would make a sun-synchronous orbit possible. - An automation and control language (like Vizzy or kOS?) that allows us to control our launcher or spacecraft in a reproducible way. - If not purposely designed, motors should have limited thrust modulation and re-ignition capabilities. I recognise that an engine that could not be modulated would not be playable by human control, so we could imagine that a non-variable thrust engine would only be allowed to modulate down to extinction. With theses limitations, monergol will be of great interest. - Liquid engines would be differentiated between MetalOx and HydroLOx to allow us to choose between a high-density liquid fuel and a low-density liquid fuel. - For re-entry capsules, we would add a selector that would shift the centre of mass, this misalignment being intended to introduce a natural angle of attack and lift.
  6. Well, I was wrong. Ariane 5 User's manuel gives 4540 kg for the dry mass. The illustration on this website gives aditional details. It includes 900 kg for the Inter Stage Skirt, but the VEB is excluded. The VEB changed between A5 G and A5 ECA. Something from 1450 kg to 950 kg when the aluminium structure has been replaced by composite structure. Acme Engineering (acme-engineering.nl)
  7. I won't help you much but I read your interrogation regarding ESC-A upper stage. I think someone has mixed up kg and lbs values of the empty mass (2100 kg / 4600 lbs) and spead the error on internet (at least on the English, French and German Wikipedia pages). I guess we should consider for ESC-A Empty mass 2100 kg (instead of 4600 kg) Fuel 14400 kg Gross mass 16500 kg (instead of 19 t) As stated here : Ariane 5-2 ESC A (astronautix.com)
  8. I'd like that too. If I am not mistaken, I understand that a scale of around x3 is more consistent with the characteristics of the parts. I would even be willing to buy a DLC aimed at experienced players and that would include one or several intermediate scales, among other things. Once the core engine has been fine-tuned, I don’t think it will require much development effort.
  9. If I am not wrong on Ariane 5, the boosters apply the thrust to the upper part of the core stage. I guess, it permits a lighter structure and would explain the large payload fraction. If you remove the booster, I think you have to use about the same mass ratio as Delta IV.
  10. There in 2019, there is some mix between euros and dollars : Space launchers: restoring Europe's space ambition - Senate (www-senat-fr.translate.goog) On the one hand, the price per kilo put into orbit has fallen since 2014 . Although no official communication on marketing prices has been made by Arianespace, the press has reported the following orders of magnitude: 130 million dollars for Ariane 64 and 80 million dollars for Ariane 62 versus, as we have seen , a Falcon 9 priced at less than $50 million in the commercial market 67( * ) . Worse, this price difference would be justified by a difference in production cost: according to the same source, the cost targets were 90.6 million euros for an Ariane 64 and 73.6 million euros for an Ariane 62 68( * ) against, as already mentioned, a cost of 44 million dollars for a consumable Falcon 9 launch .
  11. I guess adapting an expensive engine that was not designed to be reused and is moreover HydroLOx is just a dead-end. About the cost of SRBs, in a parliamentary report I found references that say prices 130 M€ for Ariane 64 and 80 M€ for Ariane 62 but it target costs 91 M€ for Ariane 64 and 74 M€ for Ariane 62. It don't know if there are up to date, but it reduces the cost of two boosters to 17 M€. I'm not very surprised, as optimizing booster production compare to A5 was a key argument to justify the Ariane 6 architecture.
  12. I always heard that hydrolox engines introduce much complexity hardly compensated by the fuel efficiency. And to get a reusable stage, I guess the engine has to be able to modulate its thruttle. On the Falcon rockets, the design was simplfied to get only 2 stages and a single engine type, that leads some ways to optimize the production. Actually the current Ariane 6 is not the most cost effective configuration that was studied. It is was a compromise between the different countries. Full solid fuel boosters on its lower stages appeared to be cheaper, Ariane 6 life will be quite short, currently there is a developpement for a MethaLOx variable thrust engine (Prometheus) that is reusable, with a goal to be one-tenth the cost of the Vulcain.
  13. Ariane cannot compete with SpaceX, they do not operate in the same markets. The launches subject to competition represent only a fraction of the total. SpaceX benefits from the U.S. market for institutional launches and launches of its own constellation. This situation cannot be compared to European institutional launches (which are not required to be launched by a European rocket). The economic equation of a reusable rocket puts Ariane at a disadvantage compared to SpaceX. The question that arises is how to build a rocket that minimizes the cost of sovereign access to space. The commercial price is only defined to diluate that cost on commercial launches.
  14. KSP2 version : It seems that some aerodynamic parts are misclassified in the VAB. I would expect parts with a control surface to be filed in the control surface folder while those without a control surface would be filed in the stabiliser folder. Currently the VAB shows this: Stabilizer folder LAF-125 (XS): Control surface available : no LPS-250 (SM): Control surface available : yes MPS-500 (MD): Control surface available : yes HPS-1000 (LG): Control surface available : yes Control Surface folder LPCS-250 (SM): Control surface available : no MPCS-500 (MD): Control surface available : no HPCS-1000 (LG): Control surface available : no
  15. Anyway, only two Ariane 5 remain. She is no more built. ESA took a gamble that Ariane 6 will take over on time et decided to stop Ariane 5 production. In case of delay, Arianespace would have partially relied on Soyuz launched at Kourou and Vega but we know story and no proven rocket is available today.
  16. With patched conic, the motion is described in a locally inertial reference frame, this is quite practical. If we go with n-body physics, in addition to the other gravitational forces, we must take into account the forces of inertia if we are not in the kerbol frame and we can continue as well with J2, solar pressure and even satellite emissivity. I can see some interest for few specific missions. In this case, why not install on these specific probes or vessels a massless engine that simulates all the orbital disturbances encountered while still remaining within a keplerian motion.
  17. We do not need n-body physics. The patched conic approximation is not without interest considering that it is/was actually used for mission planning. At least it makes the navigation calculations accessible to the player and the orbital parameters remain fixed in the absence of thrust. I don't see the point of putting in an overly complicated model that requires extra computational resources, and then having to push a button on a mod that calculates the optimal trajectory automatically. You can play with matlab, gmat or whatever for that. What I would like to see is a fictitious oblatness with a J2 effect on the orbit drift that only works when the physic is on rail. This would allow a Kerbol-synchronous orbit.
  18. The pound has a definition in imperial units, but it also existed in various other measurement systems. It may be recalled that the ounce used today for trading precious metals inherited one of them (1 troy ounce ≈ 1.097 ounces). Although I live in an all metric country, I remember going to the market with my grandmother and asking the butcher for a pound or half pound of meat, here a pound meant 500g. so 1 pound = 500g is my preference I wonder if this informal usage is widespread in Europe. I found out that this is the definition given in the customary measurements system in France. https://en.wikipedia.org/wiki/Mesures_usuelles
  19. Ariane I to IV are quite similar. On Ariane V, only the HM7 engine (60 kN LH2/LOX) of the upper stage of the ECA variant is common. The evolution from I to IV was rather KSPish, and it would be interesting to detail it. To summarise the Ariane programme, the rocket was initially designed to send about 1.5 T (payload+AKM) into the GTO. During the previous programme, Europa, there were some developments (Europa III) to increase its payload. The first stage (called Drakkar), powered by 4 Viking engines (each 700-800 kN, powered by N2O4/UDMH) was to replace the Blue Streak stage and a new large second stage powered by an LH2/LOX engine was to replace the two upper stages. The Viking engine is the descendant of the Vexin engines used on the first stage of the Diamant rocket and the second stage of the Europa I rocket. The Europa programme failed and was reborn through the Ariane programme. Ariane I is a three-stage rocket. The first stage, Drakkar, is retained. To reduce development risks, the new LH2/LOX engine is retained only for the third stage because it requires a smaller engine (HM7 60 kN). And the second stage consists of a single vacuum variant of the Viking engine. Later, to increase the payload of the rocket, the third stage was lengthened. To compensate for the lower initial T/W ratio of the first stage, in addition to the gradual increase in power of both engines (hydrazine is now added to UDMH to better stabilise the combustion), strap-on boosters were added. This is Ariane III. Ariane II is only an Ariane III without boosters intended for a lighter payload and was to be launched with partially empty tanks even at full load if I am not mistaken. Ariane IV is an Ariane III with an extended first stage and larger boosters (combination of solid and liquid fuel). The combinations are 40, 42P, 44P, 42L, 44LP, 44L (0: no boosters, P for powder, L for liquid). The liquid fuel booster uses the same Viking engine as the first stage. The Ariane 44L variant is powered by 4+4+1 Viking engines and 1 HM7B engine and can send 4.9 t in GTO compared to 1.8 t with Ariane 1. Ariane V is a different architecture with a main LH2/LOX engine (1300 kN Vulcain)and two large solid boosters. In the later evolution, ECA, the HM7B engine is used in the upper stage. Ariane VI is similar to Ariane V with the Vulcain as the main engine. The solid boosters are common with the first stage of the Vega C rocket. But the upper stage is composed of a new, larger LH2/LOX engine (Vinci 180 kN) that can be restarted. This engine was initially intended to equip the upper stage of Ariane V for its mid-life evolution.
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