Author Topic: Reviving manned Dream Chaser?  (Read 11618 times)

Offline IRobot

  • Full Member
  • ****
  • Posts: 1287
  • Portugal & Germany
  • Liked: 279
  • Likes Given: 253
Re: Reviving manned Dream Chaser?
« Reply #20 on: 07/24/2018 08:30 PM »
It's just my opinion but I think a manned craft landing safely is the most important requirement.
More important than all the other safety-critical parts of the mission?
And remember that the only crewed vehicle that did not make it in one piece had wings. So your assumptions are statistically wrong.
Also looking at the CCP assessment, if I remember correctly, the hardest risk to control/mitigate were micrometeorites. Adding wings and a plane shape would not help there in any way.

Going back to requirements, you are also wrong. The main requirement is to ferry people to and from space.
If landing safety is the most important requirement, you don't even get off ground.
And I can assure you that it will not be the most important requirement on a Mars mission. Any Mars mission will have a large failure risk.

Space has a moderate risk, let's accept it. Your view is NASA's view since Challenger, which got us nowhere in the past 30 years.

Offline BrightLight

  • Full Member
  • ****
  • Posts: 1342
  • Northern New Mexico
  • Liked: 237
  • Likes Given: 341
Re: Reviving manned Dream Chaser?
« Reply #21 on: 07/24/2018 08:43 PM »
It's just my opinion but I think a manned craft landing safely is the most important requirement.
More important than all the other safety-critical parts of the mission?
And remember that the only crewed vehicle that did not make it in one piece had wings. So your assumptions are statistically wrong.
Also looking at the CCP assessment, if I remember correctly, the hardest risk to control/mitigate were micrometeorites. Adding wings and a plane shape would not help there in any way.

Going back to requirements, you are also wrong. The main requirement is to ferry people to and from space.
If landing safety is the most important requirement, you don't even get off ground.
And I can assure you that it will not be the most important requirement on a Mars mission. Any Mars mission will have a large failure risk.

Space has a moderate risk, let's accept it. Your view is NASA's view since Challenger, which got us nowhere in the past 30 years.
This is getting OT but in short, my statement stands.  I did not say anything about the configuration of the vehicle, it is my opinion that the primary requirement at any stage of the flight including abort scenarios would demand a safe landing for the passengers. Look at it like this; the British Comet lost out to the American 707  because at the end of the flight, you had to get the passengers on the ground safely.
« Last Edit: 07/24/2018 08:52 PM by BrightLight »

Offline rayleighscatter

  • Full Member
  • ****
  • Posts: 1034
  • Maryland
  • Liked: 480
  • Likes Given: 228
Re: Reviving manned Dream Chaser?
« Reply #22 on: 07/24/2018 09:31 PM »

F9 doesn't seem to be bothered with that. And air traffic control says "thanks!".


Of course not, because if there's any issues in the launch window it stays sitting in the same place, it doesn't continue to drift along at 17,500 mph.

Reentry windows can be trickier because if you have to miss the first pass you need a bit of crossrange to make up the difference.
« Last Edit: 07/24/2018 09:33 PM by rayleighscatter »

Offline TripleSeven

  • Full Member
  • ****
  • Posts: 682
  • Istanbul turkey
  • Liked: 294
  • Likes Given: 1238
Re: Reviving manned Dream Chaser?
« Reply #23 on: 07/24/2018 09:42 PM »

F9 doesn't seem to be bothered with that. And air traffic control says "thanks!".


Of course not, because if there's any issues in the launch window it stays sitting in the same place, it doesn't continue to drift along at 17,500 mph.

Reentry windows can be trickier because if you have to miss the first pass you need a bit of crossrange to make up the difference.

or go to another airport

Offline GWH

Re: Reviving manned Dream Chaser?
« Reply #24 on: 07/25/2018 05:15 AM »
Runways are a much better alternative to landing in the ocean or tossing your heatshield down onto the desert surface IMO.
If you focus only on the final meters of your long trip, yes, you are right.

And that's the problem of driving design from a single requirement. This space plane fascination makes people wanting to justify the plane-shape by all means, like making the landing the single most important requirement.

If the focus is on minimizing recurring costs to drive the design (of a reusable spacecraft), the landing of a space plane is quite appealing.
No ship costs, no refurbishment due to salt water, no airbags or parachutes, the heat shield remains intact and doesn't contact any harmful surfaces. Those final meters can be some big dollar savings, theoretically.
Oh and it can be quickly wheeled off to a clean facility for unloading. The on the ground/water infrastructure is minimized.

Of course a propulsive landing capsule would have these same features, but that would be taking the conversation away from current commercial vehicles.


Offline jtrame

  • Full Member
  • ***
  • Posts: 300
  • W4FJT
  • Knoxville, TN
  • Liked: 77
  • Likes Given: 327
Re: Reviving manned Dream Chaser?
« Reply #25 on: 07/25/2018 03:07 PM »
A lifting body airframe (Dreamchaser being the example currently) is used to house all the necessary peripherals, tankage, landing gear, and the crew compartment.  The cornical shape of CST-100 (as an example of the capsule spacecraft) houses the same types of equipment and crew compartment within that shape, substituting landing bags and parachutes for the landing gear of course.  The outer mold line of either type of spacecraft is not a plus or minus to either design.  It's just laid out differently under the skin. 

Offline GWH

Re: Reviving manned Dream Chaser?
« Reply #26 on: 07/25/2018 06:53 PM »
Not true, crew dream chaser has everything contained in the outer moldline. Starliner makes use of a disposable service module.
Even with the disposable module on cargo dream chaser they have stated they expect very low recurring costs on the vehicle.

Offline jtrame

  • Full Member
  • ***
  • Posts: 300
  • W4FJT
  • Knoxville, TN
  • Liked: 77
  • Likes Given: 327
Re: Reviving manned Dream Chaser?
« Reply #27 on: 07/25/2018 07:20 PM »
Not true, crew dream chaser has everything contained in the outer moldline. Starliner makes use of a disposable service module.
Even with the disposable module on cargo dream chaser they have stated they expect very low recurring costs on the vehicle.

Good point.  Starliner canít return the bulk of the peripheral systems, so advantage lifting body.

Offline Elmar Moelzer

  • Senior Member
  • *****
  • Posts: 3165
  • Liked: 584
  • Likes Given: 847
Re: Reviving manned Dream Chaser?
« Reply #28 on: 07/27/2018 05:09 PM »
Not true, crew dream chaser has everything contained in the outer moldline. Starliner makes use of a disposable service module.
Even with the disposable module on cargo dream chaser they have stated they expect very low recurring costs on the vehicle.
I thought DC also had a disposable service module?

Offline Prettz

  • Full Member
  • **
  • Posts: 241
  • Atlanta, GA
  • Liked: 96
  • Likes Given: 17
Re: Reviving manned Dream Chaser?
« Reply #29 on: 07/27/2018 06:44 PM »
Not true, crew dream chaser has everything contained in the outer moldline. Starliner makes use of a disposable service module.
Even with the disposable module on cargo dream chaser they have stated they expect very low recurring costs on the vehicle.
I thought DC also had a disposable service module?
Not the crew version. All that's thrown away on that one is the spacecraft adapter.

Offline TrevorMonty

Re: Reviving manned Dream Chaser?
« Reply #30 on: 07/28/2018 06:03 PM »


It's just my opinion but I think a manned craft landing safely is the most important requirement.
More important than all the other safety-critical parts of the mission?
And remember that the only crewed vehicle that did not make it in one piece had wings.

Neither shuttle accident was due to failure of the spacecraft. One was SRB and other was damage from insulation falling off main tank.
Its like saying an aircraft design is failure due crash from a bird strike.



Offline TripleSeven

  • Full Member
  • ****
  • Posts: 682
  • Istanbul turkey
  • Liked: 294
  • Likes Given: 1238
Re: Reviving manned Dream Chaser?
« Reply #31 on: 07/28/2018 06:34 PM »


It's just my opinion but I think a manned craft landing safely is the most important requirement.
More important than all the other safety-critical parts of the mission?
And remember that the only crewed vehicle that did not make it in one piece had wings.

Neither shuttle accident was due to failure of the spacecraft. One was SRB and other was damage from insulation falling off main tank.
Its like saying an aircraft design is failure due crash from a bird strike.

no...in both cases the spacecraft system failed...as did teh management  a bird strike is "random chance" what happened with Challenger and Columbia had little random about it

Offline TrevorMonty

Re: Reviving manned Dream Chaser?
« Reply #32 on: 07/29/2018 10:30 AM »


It's just my opinion but I think a manned craft landing safely is the most important requirement.
More important than all the other safety-critical parts of the mission?
And remember that the only crewed vehicle that did not make it in one piece had wings.

Neither shuttle accident was due to failure of the spacecraft. One was SRB and other was damage from insulation falling off main tank.
Its like saying an aircraft design is failure due crash from a bird strike.

no...in both cases the spacecraft system failed...as did teh management  a bird strike is "random chance" what happened with Challenger and Columbia had little random about it
The debate wasn't about shuttle system as a whole but wing vehicle vs capsule on reentry. The shuttle vehicle didn't fail because of its design. The complete launch system that shuttle used to get to space did fail twice.

Offline Patchouli

  • Senior Member
  • *****
  • Posts: 4400
  • Liked: 182
  • Likes Given: 359
Re: Reviving manned Dream Chaser?
« Reply #33 on: 07/30/2018 12:48 AM »
The debate wasn't about shuttle system as a whole but wing vehicle vs capsule on reentry. The shuttle vehicle didn't fail because of its design. The complete launch system that shuttle used to get to space did fail twice.

Agreed the orbiter part of the system was very reliable so long as there were no anomalies during launch.
The aircraft style landing mode is so far in practice has been the safest way to bring back a vehicle.

When you think about how many accidents have happened the method used by Soyuz is actually fairly dangerous in comparison.

« Last Edit: 07/30/2018 01:02 AM by Patchouli »

Offline jbenton

  • Full Member
  • **
  • Posts: 218
  • Liked: 57
  • Likes Given: 214
Re: Reviving manned Dream Chaser?
« Reply #34 on: 07/30/2018 11:29 AM »
The debate wasn't about shuttle system as a whole but wing vehicle vs capsule on reentry. The shuttle vehicle didn't fail because of its design. The complete launch system that shuttle used to get to space did fail twice.

Agreed the orbiter part of the system was very reliable so long as there were no anomalies during launch.
The aircraft style landing mode is so far in practice has been the safest way to bring back a vehicle.

When you think about how many accidents have happened the method used by Soyuz is actually fairly dangerous in comparison.

I also agree:

1) Crewed Dream Chaser has launch abort for the whole launch envelope; Repeat of Challenger is no more likely than it would be for a capsule. Further, liquid boosters are inherently safer than solids. ULA seems pretty committed to replacing Atlas 421/422 with Vulcan-Centaur 402 ASAP. If they do get a first launch by 2020, then the first Crewed Dream Chaser would probably be on one of those.
2) Dream Chaser is on top which - as previously mentioned - makes a repeat of Columbia impossible.
3) The greatest risk to Shuttle (at least according to studies) was indeed MMOD, but Dream Chaser is a much smaller target.
4) I don't know where I read this, but apparently some people think that they could've saved Columbia with a skip re-entry if they had known that there was a problem.

https://en.wikipedia.org/wiki/Boost-glide

5) Mismanagement is less likely to be a problem this time, provided that there aren't any absurd self-imposed schedule constraints. In 1988, they flew STS nine times in one year. And human error can happen just as much to a capsule as a spaceplane.

Offline envy887

  • Senior Member
  • *****
  • Posts: 4630
  • Liked: 2552
  • Likes Given: 1397
Re: Reviving manned Dream Chaser?
« Reply #35 on: 07/30/2018 01:53 PM »
The debate wasn't about shuttle system as a whole but wing vehicle vs capsule on reentry. The shuttle vehicle didn't fail because of its design. The complete launch system that shuttle used to get to space did fail twice.

Agreed the orbiter part of the system was very reliable so long as there were no anomalies during launch.
The aircraft style landing mode is so far in practice has been the safest way to bring back a vehicle.

When you think about how many accidents have happened the method used by Soyuz is actually fairly dangerous in comparison.

It's not so much "aircraft style", as "glider style". You only get one approach attempt, it's either land or crash.

Parachutes are quite reliable also. Once they are deployed, they have few catastrophic failure modes and lots of redundancy.

Online ChrisWilson68

  • Senior Member
  • *****
  • Posts: 3750
  • Sunnyvale, CA
  • Liked: 2361
  • Likes Given: 3041
Re: Reviving manned Dream Chaser?
« Reply #36 on: 07/30/2018 02:17 PM »
The debate wasn't about shuttle system as a whole but wing vehicle vs capsule on reentry. The shuttle vehicle didn't fail because of its design. The complete launch system that shuttle used to get to space did fail twice.

Agreed the orbiter part of the system was very reliable so long as there were no anomalies during launch.
The aircraft style landing mode is so far in practice has been the safest way to bring back a vehicle.

You need to add the qualifier "no anomalies during launch", but that's not really a fair way of judging it since the anomaly on launch was something that happened only because it was a winged design.

Winged designs cause all sorts of other design decisions.  With Columbia, one of the design decisions caused by going with a winged design caused the loss of Columbia.  It's not fair to absolve the winged design of that failure because it's a direct result of the winged design.  A capsule would not have failed this way.

Winged designs have a worse rate of killing people than capsules.  Maybe future winged designs will be safer, but that's the nature of looking at historical results.  The historical results, so far, say that winged designs are less safe.

Other winged designs in the future may not have the same failures that have been seen in the past.  But the fundamental underlying cause is still there: winged designs are more complex, and that added complexity causes trade-offs throughout the system, trade-offs that can lead to loss of the crew.

Offline bad_astra

  • Full Member
  • ****
  • Posts: 1862
  • Liked: 252
  • Likes Given: 306
Re: Reviving manned Dream Chaser?
« Reply #37 on: 07/31/2018 03:43 PM »

You need to add the qualifier "no anomalies during launch", but that's not really a fair way of judging it since the anomaly on launch was something that happened only because it was a winged design.

Winged designs cause all sorts of other design decisions.  With Columbia, one of the design decisions caused by going with a winged design caused the loss of Columbia.  It's not fair to absolve the winged design of that failure because it's a direct result of the winged design.  A capsule would not have failed this way.

Winged designs have a worse rate of killing people than capsules.  Maybe future winged designs will be safer, but that's the nature of looking at historical results.  The historical results, so far, say that winged designs are less safe.

Other winged designs in the future may not have the same failures that have been seen in the past.  But the fundamental underlying cause is still there: winged designs are more complex, and that added complexity causes trade-offs throughout the system, trade-offs that can lead to loss of the crew.


The main problem was not the wings, it was the side mounting. A capsule astride a Shuttle-C would have also been subject to debris strikes. This is not to say that wings or lifting bodies don't present problems, but they are resolvable.
The death rate aboard winged vehicles is higher simply because STS flew more people.
"Contact Light" -Buzz Aldrin

Online octavo

  • Full Member
  • *
  • Posts: 129
  • Liked: 64
  • Likes Given: 174
Re: Reviving manned Dream Chaser?
« Reply #38 on: 08/13/2018 11:09 AM »

The main problem was not the wings, it was the side mounting. A capsule astride a Shuttle-C would have also been subject to debris strikes. This is not to say that wings or lifting bodies don't present problems, but they are resolvable.
The death rate aboard winged vehicles is higher simply because STS flew more people.

I think Chris' point was that the decision to have a winged vehicle resulted in another decision to fly side-mounted. Therefore the disaster was at least partially the result of a decision to use a winged vehicle. I think.

Offline TripleSeven

  • Full Member
  • ****
  • Posts: 682
  • Istanbul turkey
  • Liked: 294
  • Likes Given: 1238
Re: Reviving manned Dream Chaser?
« Reply #39 on: 08/13/2018 11:20 AM »
The debate wasn't about shuttle system as a whole but wing vehicle vs capsule on reentry. The shuttle vehicle didn't fail because of its design. The complete launch system that shuttle used to get to space did fail twice.

Agreed the orbiter part of the system was very reliable so long as there were no anomalies during launch.
The aircraft style landing mode is so far in practice has been the safest way to bring back a vehicle.

You need to add the qualifier "no anomalies during launch", but that's not really a fair way of judging it since the anomaly on launch was something that happened only because it was a winged design.

Winged designs cause all sorts of other design decisions.  With Columbia, one of the design decisions caused by going with a winged design caused the loss of Columbia.  It's not fair to absolve the winged design of that failure because it's a direct result of the winged design.  A capsule would not have failed this way.

Winged designs have a worse rate of killing people than capsules.  Maybe future winged designs will be safer, but that's the nature of looking at historical results.  The historical results, so far, say that winged designs are less safe.

Other winged designs in the future may not have the same failures that have been seen in the past.  But the fundamental underlying cause is still there: winged designs are more complex, and that added complexity causes trade-offs throughout the system, trade-offs that can lead to loss of the crew.

I dont  agree with that

the shuttle "system" (a more precise word than spacecraft I admit) failed because 1) the design had some inherent defects 2) NASA insisted on flying the system with those defects, 3) they insisted on flying the system in an environment where the defect(s) got worse and 4) ignored a known event and did nothing to verify that the vehicle was safe

A capsule, side mounted on the ET/SRB stack would have concievably had exactly the same problems.  without an escape system the Challenger accident would have still been fatal...and while the foam coming off the vehicle would not have impacted a side mounted capsules "heatshield" it would have impacted the vehicle..and "could" have been catastrophic as well...

you might have a point if say an orbiter had been lost (as a lot of people thought Columbia initially was) by the difficulty of going from stalled to flying or more correctly from "controlled brick" to lifting body.

but as best I know that never was even close to being an issue

the fly by wire system on the shuttle was amazing period much less for its then novelty. on Columbia it held control of the vehicle until control was simply impossible


Tags: