But "my" point still stands that by the criteria Chris used, SpaceX was an "unproven" company despite all their "incremental" testing until they actually flew a successful, full-up flight :)
Denigrating the hard work by done by people trying for the same goal but by different means.
i don't understand the animosity toward REL.
what have they done to offend so?
to me REL brings to mind two things - the sentiment behind the quote “We choose to go to the moon in this decade and do the other things, not because they are easy, but because they are hard." and Concorde.
REL are working really hard on a disruptive idea that they had; one that they think can achieve the same as elon musk's goal of cheap rapid access to space for the benefit of mankind. good for them. that should inspire, not generate a load of naysaying. what's wrong with you people?
when the space shuttle idea was proffered, did people say 'what's wrong with normal rockets?, we know how to do normal rockets' were there naysayers arguing for incremental steps? i don't know. the result was awesome.
' what's wrong with normal aeroplanes?' and then out rolls concorde. if there were people at the time who tried to undermine the spirit of the project, i bet they were as awestruck as the rest of us when the result took off in front of them.the world has been mesmerised by spacex landing rockets and capsules; by them constructing a BFR, and then out rolls Skylon sounding like the end of the world. how is this bad? if it is difficult, if it takes a long time, are they reasons for REL to give up? of course not. the world needs passionate and competent innovators of their ilk. they should be encouraged. i wonder if this thread is getting REL down. i hope not.
Yes, I agree, SpaceX was at one time an unproven company. If we were back at the time before SpaceX had built and tested its first engine and SpaceX were making projections about how many cycles their reusable first-stage airframe could handle, I would say they didn't have enough information to be making projections like that and that such projections shouldn't be considered reliable. In fact, back then SpaceX thought that they would be reusing their first stages by putting parachutes on them, covering them with cork, and fishing them out of the sea. They even made their first engines salt-water-tolerant because of that plan. And that's exactly my point -- a company that has yet to build its first engine has a lot of unknowns in front of it.
SpaceX took a much more incremental approach, and that allowed them to learn lessons and modify their approach. Their approach was also much less of a leap beyond the existing state of the art at the time. That allowed them to deal with all those unknowns. What worries me about REL is that they seem to think they know most of the unknowns already, when I don't think they -- or anyone else -- possibly could.
Quote from: ChrisWilson68 on 02/20/2015 06:36 pmYes, I agree, SpaceX was at one time an unproven company. If we were back at the time before SpaceX had built and tested its first engine and SpaceX were making projections about how many cycles their reusable first-stage airframe could handle, I would say they didn't have enough information to be making projections like that and that such projections shouldn't be considered reliable. In fact, back then SpaceX thought that they would be reusing their first stages by putting parachutes on them, covering them with cork, and fishing them out of the sea. They even made their first engines salt-water-tolerant because of that plan. And that's exactly my point -- a company that has yet to build its first engine has a lot of unknowns in front of it.I'm going to point out that the bolded part is NOW not "back-then" as SpaceX does NOT have the data to make accurate predictions... yet.
Yes REL faces a lot of "unknowns" in assembly of their first engine but the basic technology and techniques are already in place. They have already retired two of the biggest with the heat exchanger and rocket. Their biggest hurdle continues to be money, not competence or capability. Where would SpaceX be without Musk and his money?
QuoteSpaceX took a much more incremental approach, and that allowed them to learn lessons and modify their approach. Their approach was also much less of a leap beyond the existing state of the art at the time. That allowed them to deal with all those unknowns. What worries me about REL is that they seem to think they know most of the unknowns already, when I don't think they -- or anyone else -- possibly could.Which unknowns would those be? I'm curious.
SpaceX's approach was highly conservative in most respects. They built an ELV with the idea of eventually turning it into an RLV. They then rebuilt it as an RLV but still usable as an ELV. In the end its going to remain an RLV that "can" be an ELV and in that sense its limited (and they admit this) and eventually will end up a "dead-end" no matter how successful.
But it's a start and in the right direction so kudos and I'm rooting for them.REL is aiming for a different vehicle, operational mode, and model from the start and they have far less resources than SpaceX did to do it with. That in no way makes one approach "better" than the other.
I haven't seen any evidence of animosity toward REL. None. I specifically said I hope they do succeed.
Skepticism is not the same as animosity.Skepticism is healthy. People should welcome it even if they disagree. Skepticism helps make sure the right decisions are made and makes it more likely we move forward in spaceflight, just like we all want.
The worry is in fact that REL will turn into another Concorde -- a waste of money and talent on a system that was not economically viable.
If you read my earlier post carefully, you would realize I wasn't calling for the cancellation of the technology REL is trying to develop. I was instead suggesting more caution in projections and a more flexible, incremental development approach.
I find it very sad that you interpret well-intentioned skepticism as being a character flaw. Even if you disagree with our skepticism, why can't you accept that it comes from good intentions?
A discussion of the Space Shuttle is off topic for this thread, but suffice it to say there are many people who think the Space Shuttle program was a mistake and a more incremental approach that didn't try to do so much would have been a better use of resources. Many people think the space shuttle kept of stuck in Low Earth Orbit for decades when we could have been exploring far beyond.
Blind encouragement and ignoring potential mistakes is ultimately bad for any project. True friends are honest, even if they have to say things people don't want to hear.
The two biggest hurdles technology wise were the heat exchanger and the rocket motor both of which have been demonstrated.
Quote from: ChrisWilson68 on 02/20/2015 06:55 pmI haven't seen any evidence of animosity toward REL. None. I specifically said I hope they do succeed.I don't think it's YOU that's being referred to :) I seem to recall at least one post where REL was called an outright 'fraud' which I think would be considered "animosity".
Is it perhaps that BOTH sides are missing the point that the discussion comes from "good intentions" on both sides?
QuoteBlind encouragement and ignoring potential mistakes is ultimately bad for any project. True friends are honest, even if they have to say things people don't want to hear.Yep :) Shall we proceed from that point and continue the discussion friend? :)
Quote from: RanulfC on 02/20/2015 06:57 pmThe two biggest hurdles technology wise were the heat exchanger and the rocket motor both of which have been demonstrated. The rest of your post was reasonable, but this I must inquire about:When was the rocket motor demonstrated? Did I miss that?
Quote from: Lars-J on 02/20/2015 08:15 pmQuote from: RanulfC on 02/20/2015 06:57 pmThe two biggest hurdles technology wise were the heat exchanger and the rocket motor both of which have been demonstrated. The rest of your post was reasonable, but this I must inquire about:When was the rocket motor demonstrated? Did I miss that?It appears so; there have been a number of nozzle and flow demonstrator engines built and tested by REL and their associates:STRICTSTERNSTRIDENTSTOICSTILETTOhttp://forum.nasaspaceflight.com/index.php?action=dlattach;topic=33648.0;attach=571189
I'm interested in what happens assuming they get things mostly right or what they might do if this or that issue turns out to be more difficult because the alternative is that they go bust and the world is the same as before which is a non-story - why discuss it?
We might as well mention that lots of people have built rockets before but this heat exchanger is exceptional so it speaks for their ability to come up with something unheard of and get it done right.
The DC-X clearly meets your original point which had no requirement of being in charge or the end system becoming operational. Other projects that meet that criteria plus your newly added one of operational status are the EJ200, Spey and RB211 which Richard Varvill and John Scott Scott worked on, respectively.
When are you proposing to stage this notional TSTO? Inside the atmosphere so you can use a simpler non rocket mode SABRE losing LOX tanks from the first stage or outside still using SABRE? Are you carrying the second stage internally or externally? If externally how are managing the damage that does to the aerodynamics and thermal protection? If internal how are making the vehicle trimable given the damage that does? What engine is powering the second stage? How does any of that make the development of SABRE cheaper? Either you're proposing using the SABRE design as is, or you're suggesting development of a second engine, on top of SABRE, without a pure rocket mode neither of which can be cheaper for REL as an engine developer than just building SABRE.
I can't help feel that rocketry (successfully putting things in orbit since 1957) is somewhat better understood that Scramjets ( someday soon we'll reach ten minutes cumulative flight time). Who is seriously researching scramjets for anything other than hypersonic cruise? Also please name these other people who think that the development challenges of NASP in 1984 are of comparable difficulty to the challenges of Skylon in 2015.
Many people believe that VentureStar wasn't viable, but I don't think anybody believes the X-33 couldn't have flown and gathered useful data. The X-33 wasn't VentureStar, VentureStar was a powerpoint, X-33 was an active x-plane project with a similar budget and goals to the X-15. The X-15 wasn't a failure because it had no follow on project so why should the X-33? When the X-15 first flew it didn't have it's intended engine yet because it wasn't ready, so why should the X-33 not have been given the same leeway? Like I said, there was a change in administration, a desire to cancel and repudiate the projects of the previous one, people obliged.
EDIT: To offer a more substantive response. I don't think the line between science and engineering exists as you think it does. And what scientific breakthroughs have REL done? Their pre-cooler work would be classified by most as an impressive piece of engineering.
Also on the 26th of March he's a speaker at this event:http://www.develop3dlive.com/speakers/