Quote from: gosnold on 05/28/2017 11:55 amI don't understand the choice of hydrolox for this launcher. I expect it complicates fuelling operations and the structural design of the launcher, compared to hydrocarbons. Why did they choose hydrogen? To reuse existing engine parts?Because Boeing offered it.
I don't understand the choice of hydrolox for this launcher. I expect it complicates fuelling operations and the structural design of the launcher, compared to hydrocarbons. Why did they choose hydrogen? To reuse existing engine parts?
Quote from: envy887 on 05/31/2017 02:35 amBut why use 7 tonnes for engine mass when a single SSME is 3.3 tonnes?slightly different based on RS-25 version.
But why use 7 tonnes for engine mass when a single SSME is 3.3 tonnes?
My main question remains:Why did not REL apply for this grant?
I agree with the idea of competition and trying many different paths.
What I disagree with is the government picking the winners.
This program specified the requirements too narrowly, so it funneled money into one particular path to orbit, rather than letting competition determine the most promising paths to fund.
Quote from: francesco nicoli on 05/27/2017 01:12 pmMy main question remains:Why did not REL apply for this grant?Several reasons.Jess Sponable, the PM for the project stated he wanted any proposal to have an already developed engine, since it's such a key part of the project. SABRE is not there yet and Sponable was adamant they did not want to sponsor an engine development programme. That said Boeing's decision to switch engines and abandon Blue for a design of unknown specification ("like" an SSME covers a very broad range of options) is very suspicious. IIRC REL did not have a US office at the time the project started. To compete REL would have had to a)Form a relationship with a US airframe builder b)Persuade them they would have a SABRE ready in time for the budget available or c) Persuade them they could use the win to raise more capital to develop SABRE and d)Actually raise the additional capital and develop the engine. Which given the fickleness of UK financial markets and the grudging support of the UK government (years late) would have made this a very high risk project for them. It would have also deeply enmeshed them in the US ITAR regulations making virtually any application outside the US very difficult. Sadly this may yet happen.
I wonder what the implications of the engine choice will be on the SLS program. 2 AR-22s aren't going to last long before they need a new version. Assuming they keep flying the same airframe after those engines are dead, another RS-25 or derivative of it would be useful (there's not really any alternatives in development with the same sort of performance, and unlike expendable rockets its not really feasible to stretch the tanks on a spaceplane), or even if they do replace Phantom Express with a larger vehicle a modern RS-25 could be vaguely competitive. If Boeing can convince Aerojet to have new RS-25s in production by, say, 2024 instead of 2027 (being that its a commercial project and they don't have to play nice with Aerojet for political reasons like NASA does), that eliminates the big gap in engine availability for SLS. Combine with lower costs for the SLS engines from additional commercial demand (maybe they could even fly Boeing's engines that are near end-of-life?), and SLS might be just the slightest bit less absurd (at least able to fly more than once every 2 years, anyway). Boeings engine choice here could've been intended to aid their other major project. Alternatively, if SLS is ultimately canceled before its first 4 flights are done, Boeing could get a rather large number of RS-25Ds without needing to pay for new production
A reusable suborbital spaceplane the size of a business jet being developed by Boeing and the Defense Department’s research and development arm could be launching and landing at Cape Canaveral in 2020, officials said after the defense contractor won a competition last month to design and test the vehicle.
The spacecraft booster would return to land at one of two runways on Florida’s Space Coast: Kennedy Space Center’s Shuttle Landing Facility, a three-mile-long landing strip, or the Skid Strip at Cape Canaveral Air Force Station.
“We conducted trade studies with Blue Origin in the first phase of the program,” Sampson wrote in an email to Spaceflight Now. “Boeing selected the Aerojet Rocketdyne engine for this next phase as it offers a flight proven, reusable engine to meet the DARPA mission requirements.”
Aerojet Rocketdyne said it will provide two engines for the XS-1 program with “legacy shuttle flight experience to demonstrate reusability, a wide operating range and rapid turnarounds.”
The Phantom Express booster stage will have advanced, lightweight composite cryogenic tanks to hold the super-cold propellants feeding the AR-22 engine. Hybrid metallic-composite wings and control surfaces on the spaceplane will be fitted with “third-generation thermal protection” to withstand the rigors of hypersonic flight and re-entry temperatures of more than 2,000 degrees Fahrenheit (1,100 degrees Celsius), according to DARPA and Boeing.
I'm still curious how they plan to push the XS-1 to Mach 10 while still enabling a glide back to the launch site. That's either a mighty impressive glide ratio, or the requirements are already being lowered.
Quote from: Lars-J on 06/14/2017 12:33 amI'm still curious how they plan to push the XS-1 to Mach 10 while still enabling a glide back to the launch site. That's either a mighty impressive glide ratio, or the requirements are already being lowered.Who said it would do both in the same mission? Mach 10 seems to be just a one-off test objective, not part of the operational flight profile. Certainly don't need to go that fast on a booster for an orbital flight. They can land it downrange somewhere on that test flight, and RTLS on all the llwer velocity tests and on orbital missions
Quote from: brickmack on 06/14/2017 03:22 pmQuote from: Lars-J on 06/14/2017 12:33 amI'm still curious how they plan to push the XS-1 to Mach 10 while still enabling a glide back to the launch site. That's either a mighty impressive glide ratio, or the requirements are already being lowered.Who said it would do both in the same mission? Mach 10 seems to be just a one-off test objective, not part of the operational flight profile. Certainly don't need to go that fast on a booster for an orbital flight. They can land it downrange somewhere on that test flight, and RTLS on all the llwer velocity tests and on orbital missionsI'm still curious how they are going to land downrange. Neither Vandy nor the Cape have a suitable landing strip downrange, unless they do a dog-leg and fly it up the coast?
Even an nominal orbital launch is going to make glide-back RTLS very challenging. (Mach 5+?) Will this SSME derivative engine be able to restart? If not they are limited to... A) hot staging B) glide onlyEither option is very challenging.
...The X38 was slated to have a "flush mount" ADS with more pressure sensing pipes to cope with the surface geometry effects of being mounted in the nose. I think the X37b also uses such a system. In principal these systems can operate to much higher Mach numbers, giving a much better idea of aerodynamic forces on the vehicle. I'm not sure if the X37b has been remote piloted during its landings or if this ability to more accurately generate air data has made that unnecessary.