12 ms·

> likely human rated in the future: Vulcan Centaur + Dream Chaser IMO, this one is the least likely. There are a lot of problems that need to be over come for

> likely human rated in the future: Vulcan Centaur + Dream Chaser IMO, this one is the least likely. There are a lot of problems that need to be over come for Dream Chaser to be crew rated. And AFAIK, they aren't getting NASA money to do it.

sho_hn 2y ago
> There are a lot of problems that need to be over come for Dream Chaser to be crew rated. Intriguing. Can you elaborate?
- dotnet00 2y ago
  IIRC one of the big ones is that of how the crew is supposed to board the vehicle. Cargo Dreamchaser is launched in a fairing so that its aerodynamics don't matter on the way up. This is fine because the cargo can be loaded prior to payload integration. But that won't work if they're carrying crew.
- JanSolo 2y ago
  Star Liner has all the same problems that the Space Shuttle had. In an emergency, how do you get the crew out safely?
  - nordsieck 2y ago
    > Star Liner has all the same problems that the Space Shuttle had. In an emergency, how do you get the crew out safely? Starliner has a launch abort system; the Shuttle did not. From what I understand, they use a very powerful rocket (much more powerful than Crew Dragon) to get the capsule far away from the booster. I guess it can get far enough away that NASA is satisfied that falling bits of burning SRB aren't a danger to the parachutes.
    - somenameforme 2y ago
      During the Starline abort test only 2 of the 3 parachutes opened, and that was a pad abort test - no SRBs!! NASA not only calling that a "success", but a sufficient success to move onto crewed testing was about the moment I lost all faith in Bridenstine being different. Immediately after leaving office he picked up a cushy consulting type gigs for various aerospace/defense companies (aka Boeing et al). Shocker. For those who might not know SRB = solid rocket booster. Boeing uses them, SpaceX doesn't. An SRB is basically like a giant firecracker. You light it and it starts burning and doesn't stop until its done. It poses substantial safety concerns in the case of an accident where you need to abort the flight. But they're cheap, extremely powerful, and relatively simple contrasted against liquid fuel engines.
      - tekla 2y ago
        Failure of 1 chute was designed for, though yes, it wasn't a great look. > It poses substantial safety concerns in the case of an accident where you need to abort the flight SRBs are in general very safe, which is why they're still used for human rated rockets.
        somenameforme 2y ago
        Well we shall see I suppose. SRB's go back to the Apollo era and NASA safety qualifications often come down to 'are you doing what we've done before'? Hence them refusing to even consider SpaceX retropulsive crew landings, even though that would be a huge step forward. I would also observe that NASA has a relatively poor safety record contrasted against the Soyuz (which has not lost crew since 1971 in spite of flying more manned missions), and one of the few completely catastrophic crashes we have had, Challenger, was directly related to the SRB. In either case, I expect variance is playing a much larger role than most might appreciate.
      - philwelch 2y ago
        While I share your reservations with solid rockets as a main propulsion system on a manned rocket, it turns out they are well suited for launch escape systems themselves for some of the same exact reasons: they’re simple and powerful.
    - wkat4242 2y ago
      Didn't the shuttle have this harebrained thing where the crew were supposed to climb all the way to the exit hatch in their pressure suits, extend a boom along the wing in full flight and then parachute out along it? I thought I read about that. Of course that's effectively no actual escape system lol. They'd be long dead by the time they managed all that in an out of control shuttle.
      - tekla 2y ago
        It was a proposed mechanism that was never taken really seriously.
        nordsieck 2y ago
        > It was a proposed mechanism that was never taken really seriously. I guess it depends on what you mean by that. Astronauts were trained on the system and it was aboard the shuttle. Did the astronauts believe that it's likely that the system would save them? Probably not. https://www.smithsonianmag.com/air-space-magazine/escape-speeding-shuttle-180975606/ https://www.smithsonianmag.com/air-space-magazine/escape-spe...
        wkat4242 2y ago
        > Did the astronauts believe that it's likely that the system would save them? Probably not. Yeah personally I would have taken my chances ditching the craft, tbh. It would probably ditch pretty well considering it doesn't have huge engine pods under the wings.
      - dlgeek 2y ago
        Yep. That's supposedly for them to ditch in the event that the main engines fail but the shuttle is controllable - they don't have enough energy for a trans-atlantic abort, so they glide and bail out over the ocean. Harebrained is right.
        dylan604 2y ago
        No idea is a bad idea, but it can be harebrained. How far did this plan go? Just because it was discussed and documented and thought through does not mean it was something that was actually going to happen. Was this actually developed and the parts&pieces put into place with procedures written up in the flight manual?
  - lupusreal 2y ago
    Starliner is put on top of the rocket, not next to it.
  - throwawaymaths 2y ago
    Pretty sure Star liner is at the top of its stack, so there is no risk of sheets of ice falling on it and damaging it
  - tekla 2y ago
    What? No it doesn't.
  - wolfendin 2y ago
    It can’t have “all the same problems” because a number of the engineering problems came from having the spacecraft on the side of the launch vehicle
- nordsieck 2y ago
  The big one off the top of my head: Dream Chaser flies in a fairing for aerodynamic reasons. In order to fly crew (so that the vehicle could have a working launch abort system), they'd need to figure out how to fly without a fairing.
  - SJC_Hacker 2y ago
    Can't they blow the fairing as part of launch abort?
    - nordsieck 2y ago
      > Can't they blow the fairing as part of launch abort? I'm not a rocket scientist, so I don't really know the answer. But I have some questions: * How reliable will the "blow the fairing" system be? If it's only used in emergencies (instead of the regular fairing separation mechanism) than it'll suffer from the same problem as emergency generators - they're rarely tested and fail very often when needed. * How easy is it to get the fairing out of the way once it's opened? Normally, regular aerodynamic forces slough the fairing halves off, but an LES/LAS doesn't have time for that - it's escaping a potentially exploding rocket. And those fairings will act like sails - huge surface area:volume ratio means they're just not going to move fast. * What happens if DreamChaser hits one of the fairings on the wing? Would it damage it enough that it'd have trouble landing? Is it enough to cause it to foul the escape trajectory? Or even put it in a spin? It seems like a lot of work to get it to work with or without a fairing.
    - giantrobot 2y ago
      That's one more thing to go wrong. In a LES scenario something(s) has gone wrong in an unrecoverable way. Very few systems can be relied upon to exist let alone work correctly. A LES on a crewed capsule is supposed to be able to pull itself from the vehicle all under its own power. It can't assume explosive fasteners on the fairing are functional or actual all function correctly. You don't want the LES to activate, seem to be working correctly, and then blast the crew into a fairing panel that did not fully separate. The crew doesn't have time to roll down the window and kick it loose.
    - 2y ago
glenstein 2y ago
>There are a lot of problems that need to be over come for Dream Chaser to be crew rated. Thanks, this is helpful to know. What do you know about the dream chaser problems?

sho_hn 2y ago

> There are a lot of problems that need to be over come for Dream Chaser to be crew rated. Intriguing. Can you elaborate?

dotnet00 2y ago
IIRC one of the big ones is that of how the crew is supposed to board the vehicle. Cargo Dreamchaser is launched in a fairing so that its aerodynamics don't matter on the way up. This is fine because the cargo can be loaded prior to payload integration. But that won't work if they're carrying crew.
JanSolo 2y ago
Star Liner has all the same problems that the Space Shuttle had. In an emergency, how do you get the crew out safely?
- nordsieck 2y ago
  > Star Liner has all the same problems that the Space Shuttle had. In an emergency, how do you get the crew out safely? Starliner has a launch abort system; the Shuttle did not. From what I understand, they use a very powerful rocket (much more powerful than Crew Dragon) to get the capsule far away from the booster. I guess it can get far enough away that NASA is satisfied that falling bits of burning SRB aren't a danger to the parachutes.
  - somenameforme 2y ago
    During the Starline abort test only 2 of the 3 parachutes opened, and that was a pad abort test - no SRBs!! NASA not only calling that a "success", but a sufficient success to move onto crewed testing was about the moment I lost all faith in Bridenstine being different. Immediately after leaving office he picked up a cushy consulting type gigs for various aerospace/defense companies (aka Boeing et al). Shocker. For those who might not know SRB = solid rocket booster. Boeing uses them, SpaceX doesn't. An SRB is basically like a giant firecracker. You light it and it starts burning and doesn't stop until its done. It poses substantial safety concerns in the case of an accident where you need to abort the flight. But they're cheap, extremely powerful, and relatively simple contrasted against liquid fuel engines.
    - tekla 2y ago
      Failure of 1 chute was designed for, though yes, it wasn't a great look. > It poses substantial safety concerns in the case of an accident where you need to abort the flight SRBs are in general very safe, which is why they're still used for human rated rockets.
      - somenameforme 2y ago
        Well we shall see I suppose. SRB's go back to the Apollo era and NASA safety qualifications often come down to 'are you doing what we've done before'? Hence them refusing to even consider SpaceX retropulsive crew landings, even though that would be a huge step forward. I would also observe that NASA has a relatively poor safety record contrasted against the Soyuz (which has not lost crew since 1971 in spite of flying more manned missions), and one of the few completely catastrophic crashes we have had, Challenger, was directly related to the SRB. In either case, I expect variance is playing a much larger role than most might appreciate.
    - philwelch 2y ago
      While I share your reservations with solid rockets as a main propulsion system on a manned rocket, it turns out they are well suited for launch escape systems themselves for some of the same exact reasons: they’re simple and powerful.
  - wkat4242 2y ago
    Didn't the shuttle have this harebrained thing where the crew were supposed to climb all the way to the exit hatch in their pressure suits, extend a boom along the wing in full flight and then parachute out along it? I thought I read about that. Of course that's effectively no actual escape system lol. They'd be long dead by the time they managed all that in an out of control shuttle.
    - tekla 2y ago
      It was a proposed mechanism that was never taken really seriously.
      - nordsieck 2y ago
        > It was a proposed mechanism that was never taken really seriously. I guess it depends on what you mean by that. Astronauts were trained on the system and it was aboard the shuttle. Did the astronauts believe that it's likely that the system would save them? Probably not. https://www.smithsonianmag.com/air-space-magazine/escape-speeding-shuttle-180975606/ https://www.smithsonianmag.com/air-space-magazine/escape-spe...
        wkat4242 2y ago
        > Did the astronauts believe that it's likely that the system would save them? Probably not. Yeah personally I would have taken my chances ditching the craft, tbh. It would probably ditch pretty well considering it doesn't have huge engine pods under the wings.
    - dlgeek 2y ago
      Yep. That's supposedly for them to ditch in the event that the main engines fail but the shuttle is controllable - they don't have enough energy for a trans-atlantic abort, so they glide and bail out over the ocean. Harebrained is right.
      - dylan604 2y ago
        No idea is a bad idea, but it can be harebrained. How far did this plan go? Just because it was discussed and documented and thought through does not mean it was something that was actually going to happen. Was this actually developed and the parts&pieces put into place with procedures written up in the flight manual?
- lupusreal 2y ago
  Starliner is put on top of the rocket, not next to it.
- throwawaymaths 2y ago
  Pretty sure Star liner is at the top of its stack, so there is no risk of sheets of ice falling on it and damaging it
- tekla 2y ago
  What? No it doesn't.
- wolfendin 2y ago
  It can’t have “all the same problems” because a number of the engineering problems came from having the spacecraft on the side of the launch vehicle
nordsieck 2y ago
The big one off the top of my head: Dream Chaser flies in a fairing for aerodynamic reasons. In order to fly crew (so that the vehicle could have a working launch abort system), they'd need to figure out how to fly without a fairing.
- SJC_Hacker 2y ago
  Can't they blow the fairing as part of launch abort?
  - nordsieck 2y ago
    > Can't they blow the fairing as part of launch abort? I'm not a rocket scientist, so I don't really know the answer. But I have some questions: * How reliable will the "blow the fairing" system be? If it's only used in emergencies (instead of the regular fairing separation mechanism) than it'll suffer from the same problem as emergency generators - they're rarely tested and fail very often when needed. * How easy is it to get the fairing out of the way once it's opened? Normally, regular aerodynamic forces slough the fairing halves off, but an LES/LAS doesn't have time for that - it's escaping a potentially exploding rocket. And those fairings will act like sails - huge surface area:volume ratio means they're just not going to move fast. * What happens if DreamChaser hits one of the fairings on the wing? Would it damage it enough that it'd have trouble landing? Is it enough to cause it to foul the escape trajectory? Or even put it in a spin? It seems like a lot of work to get it to work with or without a fairing.
  - giantrobot 2y ago
    That's one more thing to go wrong. In a LES scenario something(s) has gone wrong in an unrecoverable way. Very few systems can be relied upon to exist let alone work correctly. A LES on a crewed capsule is supposed to be able to pull itself from the vehicle all under its own power. It can't assume explosive fasteners on the fairing are functional or actual all function correctly. You don't want the LES to activate, seem to be working correctly, and then blast the crew into a fairing panel that did not fully separate. The crew doesn't have time to roll down the window and kick it loose.
  - 2y ago

glenstein 2y ago

>There are a lot of problems that need to be over come for Dream Chaser to be crew rated. Thanks, this is helpful to know. What do you know about the dream chaser problems?