The biggest issue is heat shield, how reuseable will be. Lighter it is shorter its life before needing refurbishing. Rest of dry mass design is well understood. Shuttle and X37 are the only reuseable winged vehicles with any orbital reuse history. How is X37 heat shield holding up?Sent from my SM-G570Y using Tapatalk
Quote from: TrevorMonty on 01/20/2022 10:53 pmThe biggest issue is heat shield, how reuseable will be. Lighter it is shorter its life before needing refurbishing. Rest of dry mass design is well understood. Shuttle and X37 are the only reuseable winged vehicles with any orbital reuse history. How is X37 heat shield holding up?Sent from my SM-G570Y using TapatalkI'd imagine the X-37B's heat shield is doing much better than Radian One's would, since X-37B is a much smaller vehicle (on account of not needing to get itself into space).
Quote from: Craftyatom on 11/30/2020 05:55 pm…Material selection hasn't been made yet, but short-lists composites, Aluminum, Titanium, and Stainless Steel. …Lol, basically any possible aerospace structural material.
…Material selection hasn't been made yet, but short-lists composites, Aluminum, Titanium, and Stainless Steel. …
The launch sled is a good idea, especially as it helps enable aborting the takeoff. Big brakes to stop after coming up to speed would be not viable for a SSTO vehicle without a sled. And getting it up to transonic speeds or so would be a very nice little assist as well, considering rockets burn up a lot of their propellant just to get off the pad. Rockets are least efficient at low speeds, so that small assist goes a long way.And with the sled, they can also do captive tests of the vehicle without actually taking flight. That is easier from a regulatory standpoint (I don’t think it needs regulatory approval from the FAA), and they can even do tests before the wings are ready. They could do non-destructive qualifying tests on the airframe and propulsion systems. It’s actually a pretty good idea, to be honest. To enable the same thing without wings would mean you’d have to build a vertical launch assist tower, which would be a lot harder and more expensive.
Quote from: JEF_300 on 01/20/2022 08:48 pmOn the actual topic of Radian's SSTO, I think it is a much more plausible proposal than most have given it credit for. - It uses engines of a manageable size to develop. - It's using a denser propellant than Hydrogen, as the SSTO experts seem to have decided is best. - This seems to avoid the classic SSTO trap of assuming that some wonder technology is going to magically make it all work. - Aerospace technology in general, and materials science in particular, has advanced dramatically since the last major attempts in the late 90s. Hopefully that means that the margins are more manageable than razor thin. Or, at least the very least are back-of-the-razorblade thin rather than edge-of-the-razorblade thin.I'd suggest that it's a good deal more plausible a vehicle than past SSTOs, at the very least.Any SSTO vehicle will need to have empty weight under 5% of the all up launch weight. That is still hugely difficult.
On the actual topic of Radian's SSTO, I think it is a much more plausible proposal than most have given it credit for. - It uses engines of a manageable size to develop. - It's using a denser propellant than Hydrogen, as the SSTO experts seem to have decided is best. - This seems to avoid the classic SSTO trap of assuming that some wonder technology is going to magically make it all work. - Aerospace technology in general, and materials science in particular, has advanced dramatically since the last major attempts in the late 90s. Hopefully that means that the margins are more manageable than razor thin. Or, at least the very least are back-of-the-razorblade thin rather than edge-of-the-razorblade thin.I'd suggest that it's a good deal more plausible a vehicle than past SSTOs, at the very least.
Hah. Not sure about that but the team does have 1-2 things up their sleeve technically that haven’t been considered before. When those features are known by the wider community, I think the viability of their approach will be better understood. Still a very hard problem though.
the team does have 1-2 things up their sleeve technically
Put otherwise: if we suppose the Radian rocketplane weights 200 tons ready for takeoff, then 190 tons must be kerosene and LOX inside the tanks.The "physical" rocketplane with the payload inside must be 10 metric tons.
Remember, Earth orbit for kerolox is (roughly) 9400 m/s - or bust. Not 9250 m/s, not 9000 m/s: 9400. Any small "gap" and its over.
What I don't understand is what does SSTO buy you over a streamlined TSTO system that's compromised of two independent rapidly reusable vehicles.[ . . . ]I see the allure when compared with a traditional "pieces fall off" type rocket, but I just don't see the motivation at the present time.
Quote from: meekGee on 01/21/2022 04:29 amWhat I don't understand is what does SSTO buy you over a streamlined TSTO system that's compromised of two independent rapidly reusable vehicles.[ . . . ]I see the allure when compared with a traditional "pieces fall off" type rocket, but I just don't see the motivation at the present time.When reading about previous single-stage-to-orbit efforts, I have gotten the impression that the operation of stacking of multiple stages were at least seen as something slow and laborious. It seemed to me that the assumption was that stacking would take several days, perhaps even weeks, and thus be detrimental to rapid reflight. Possibly informed by e.g. the space shuttle, which needed to be moved to the separate Vehicle Assembly Building, mated to its very large and heavy SRBs, and then slowly transported on the crawler-transporter to the launch pad.What they wanted was "airliner-like operations", where the just-landed vehicle could just be hooked up to a tow truck, dragged to the launch pad, be raised to vertical, fuelled, and launched again within a few hours.(Admittedly, my impression of how stacking was seen, has been formed mostly by reading between the lines of third-party descriptions of those SSTO efforts.)But I think we can agree that at assumptions that stacking has to be slow, are incorrect. Properly designed, with both the first stage and the upper stage/spacecraft landing next to the launch pad, and things actually designed for easy and rapid mating, it should be possible to get them stacked and ready for reflight in a couple of hours.
What I don't understand is what does SSTO buy you over a streamlined TSTO system that's compromised of two independent rapidly reusable vehicles.I mean by definition you'll be lugging your first stage to orbit and then re-entering it.Not only will it be more complex and expensive, but you also won't have it back in 20 minutes to launch again..I see the allure when compared with a traditional "pieces fall off" type rocket, but I just don't see the motivation at the present time.
Quote from: lrk on 12/09/2020 03:33 pmHaving wings (even with a mediocre TWR) should actually help gravity losses significantly as the lift offsets gravity early in flight when losses would otherwise be the highest. Recall that the wings on the Pegasus rocket actually increased the payload capacity, despite the added mass. The lead developer for Pegasus answered questions on the development process on the Pegasus thread some years back. I recall coming across an old Pop Sci article written around the time the original version first launched which also talked about their approach Orbital was strapped for cash at the time. They'd gone in big developing the Inertial Upper Stage for the Shuttle then Challenger happened so were looking for a new project to use their rocket knowledge and get some cash in. IOW they wouldn't have added wings to the design unless it gave substantial benefits to justify having them made. Keep in mind the wing has no propellant storage or control surfaces (fins on the rear of the first stage provide those).
Having wings (even with a mediocre TWR) should actually help gravity losses significantly as the lift offsets gravity early in flight when losses would otherwise be the highest. Recall that the wings on the Pegasus rocket actually increased the payload capacity, despite the added mass.
1. The ability to operate from a runway, even if you have to drag a launch sled along with you to do it, dramatically simplifies your ground handling and infrastructure. It also gives you more flexibility when deciding where to launch from.
2. Being an SSTO, no time or money (money is the far more important part) has to be spent between flights on vehicle integration, only payload integration. Yes, stage integration has historically been far less efficient than it could be. That doesn't change the fact that no integration is still faster and cheaper, particularly since that means you don't need to build and/or maintain and/or travel-to the facilities needed for stage integration. (Unless you decided to use a launch sled, in which case I guess reintegration with the sled is basically stage integration. I really don't like the sled.)
3. Even SpaceX isn't seriously consider launching the same vehicle more than once a day, so having to wait at least 90 minutes to get the vehicle back is hardly an issue.
4. This is in some ways more of an idle thought than a point. I would also think that a reusable TSTO should be inherently simpler than an SSTO. That said, the main example we have of a RTSTO design is Starship, which is using the most complicated rocket engine ever developed. Only time will tell, but it may be the most teams designing RTSTOs willingly give up their simplicity advantage in favor of further boosting their performance advantage.
Also, between the sled probably needing to be on rails, and the runway needing to support extreme heat loads, you're not taking this rocket sled to an arbitrary runway: it's fixed to a single launch site, same as the launch tower.
Quote from: JEF_300 on 01/21/2022 08:23 pm1. The ability to operate from a runway, even if you have to drag a launch sled along with you to do it, dramatically simplifies your ground handling and infrastructure. It also gives you more flexibility when deciding where to launch from.How is a rocket sled cheaper than a launch tower? The tower is a single static piece of infrastructure, it doesn't need to move at supersonic speeds, so I would imagine it's much cheaper to build and maintain. And you'd need the same fueling infrastructure in either case.
Quote from: JEF_3002. Being an SSTO, no time or money (money is the far more important part) has to be spent between flights on vehicle integration, only payload integration. Yes, stage integration has historically been far less efficient than it could be. That doesn't change the fact that no integration is still faster and cheaper, particularly since that means you don't need to build and/or maintain and/or travel-to the facilities needed for stage integration. (Unless you decided to use a launch sled, in which case I guess reintegration with the sled is basically stage integration. I really don't like the sled.)The question is whether the extra refurbishment necessary because the entire vehicle went to space and not just the much-smaller upper stage is more time-consuming and expensive than using a crane to stack a TSTO back together. My expectation would be "yes."
