Author Topic: Basic Rocket Science Q & A  (Read 271188 times)

Online Coastal Ron

  • Senior Member
  • *****
  • Posts: 3327
  • I live... along the coast
  • Liked: 2124
  • Likes Given: 2562
Re: Basic Rocket Science Q & A
« Reply #940 on: 08/28/2014 04:38 PM »
Strange that NASA is happy to fly their reusable vehicle multiply times, but don't trust a private company's reusable vehicle. NB Orion is also planned to be reused a few times.
Garrett (Reisman, not me; I always find it weird talking about namesakes) said it would complicate the certification process. So the decision not to offer reused Dragons was made by SpaceX, not NASA. Now, whether NASA's certification process deserves criticism is another story ...

Like others have said, I think the decision to not bid reuse at this time is because there are so many unknowns that they still need to discover before they can feel confident that they are ready to offer reusability for Dragon V2.  The first being that they will be flying a brand new design spacecraft, and landing it in a new way (i.e. on land instead of water, or at least that's the goal).

Right now they have a production line set up for building new Dragons, but reusability means they have to set up a facility/workspace and process for refurbishing vehicles that have just flown.  That takes different types of skills, and though you can share some of the same people it makes sense to have dedicated personnel that can become experts on refurbishment and recertification.

I would imagine that they will want to have vehicle reusability ready for service for the follow on Commercial Crew service contract (~2020?).
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Offline jtrame

  • Full Member
  • **
  • Posts: 290
  • W4FJT
  • Knoxville, TN
  • Liked: 71
  • Likes Given: 299
Re: Basic Rocket Science Q & A
« Reply #941 on: 08/28/2014 04:40 PM »
You don't need to send ships out to fish the capsule out of the water, and you have much less chance of seawater leaking in.

You can avoid those also by landing on ground with parachutes like Soyuz and Shenzhou (albeit using last second retro rockets).

In fact, Dragon V2 will initially use the combination of parachutes and retro cushioning at landing.  Eventually, they will make the change to totally propulsive landings.

Offline aero

  • Senior Member
  • *****
  • Posts: 2739
  • 92129
  • Liked: 704
  • Likes Given: 236
Re: Basic Rocket Science Q & A
« Reply #942 on: 08/28/2014 04:43 PM »
Don't overlook the possible impact damage for parachute landings, or the added mass to LEO (reduced payload) of the landing thrusters being carried all the way up instead of discarded.
Retired, working interesting problems

Online Robotbeat

  • Senior Member
  • *****
  • Posts: 26870
  • Minnesota
  • Liked: 6775
  • Likes Given: 4805
Re: Basic Rocket Science Q & A
« Reply #943 on: 08/28/2014 04:52 PM »
Don't overlook the possible impact damage for parachute landings, or the added mass to LEO (reduced payload) of the landing thrusters being carried all the way up instead of discarded.
if you don't bring them to LEO, they'd basically have to be expendable.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline clongton

  • Expert
  • Senior Member
  • *****
  • Posts: 10271
  • Connecticut
    • Direct Launcher
  • Liked: 2035
  • Likes Given: 623
Re: Basic Rocket Science Q & A
« Reply #944 on: 08/29/2014 12:35 AM »
Soyuz has had partial parachute failures

Apollo has three main chutes while Soyuz has only one. When Apollo 15's chute failed it still had two more to bring it down. The Soyuz chute failure killed the cosmonaut because the spacecraft impacted the ground at terminal velocity.
Chuck - DIRECT co-founder
I started my career on the Saturn-V F-1A engine

Offline dglow

  • Full Member
  • ****
  • Posts: 713
  • California
  • Liked: 523
  • Likes Given: 1248
Re: Basic Rocket Science Q & A
« Reply #945 on: 08/29/2014 12:44 AM »
So Reisman (re-)confirmed terra firma landings for Dv2... but has anyone indicated where such landings might take place?

Offline Proponent

  • Senior Member
  • *****
  • Posts: 5106
  • Liked: 768
  • Likes Given: 528
Re: Basic Rocket Science Q & A
« Reply #946 on: 08/29/2014 04:39 AM »
Soyuz has had partial parachute failures

Apollo has three main chutes while Soyuz has only one. When Apollo 15's chute failed it still had two more to bring it down. The Soyuz chute failure killed the cosmonaut because the spacecraft impacted the ground at terminal velocity.

Soyuz I (like, e.g., Mercury) had a back-up 'chute.  It's just that it failed too, because its compartment was affected by the same manufacturing flaw that prevented the main 'chute from working properly.

Offline mgfitter

  • Member
  • Posts: 98
  • Liked: 13
  • Likes Given: 0
Re: Basic Rocket Science Q & A
« Reply #947 on: 09/04/2014 09:12 PM »
Not sure if this is the best thread for this question, so mods, please move it to wherever it needs to be.

After 50+ years of continued developments in human spaceflight technologies, why is it that communications between the ground and crews aboard orbiting spacecraft (and launching ones too) are still so poor in terms of audio quality?

What is the technical bottleneck that causes this?

Surely it must be technically possible to get at least Skype-like audio quality these days?

Are there any plans for Orion/Dragon/CST-100/Dreamchaser to improve things in this area?

-MG.

Offline Jim

  • Night Gator
  • Senior Member
  • *****
  • Posts: 31222
  • Cape Canaveral Spaceport
  • Liked: 9494
  • Likes Given: 298
Re: Basic Rocket Science Q & A
« Reply #948 on: 09/05/2014 12:47 AM »
Not sure if this is the best thread for this question, so mods, please move it to wherever it needs to be.

After 50+ years of continued developments in human spaceflight technologies, why is it that communications between the ground and crews aboard orbiting spacecraft (and launching ones too) are still so poor in terms of audio quality?


What makes you think it is poor quality?

Offline SWGlassPit

  • I break space hardware
  • Full Member
  • ****
  • Posts: 437
  • Liked: 249
  • Likes Given: 35
Re: Basic Rocket Science Q & A
« Reply #949 on: 09/05/2014 02:47 PM »
When ISS does media events, they use live HD video with audio quality equivalent to any other television production.  For day-to-day events, the audio only needs to be comfortably intelligible, not silky-smooth.  Why waste downlink bandwidth on an unnecessarily high audio bitrate when you can use it for more meaningful telemetry?

Offline clongton

  • Expert
  • Senior Member
  • *****
  • Posts: 10271
  • Connecticut
    • Direct Launcher
  • Liked: 2035
  • Likes Given: 623
Re: Basic Rocket Science Q & A
« Reply #950 on: 09/05/2014 08:50 PM »
Why waste downlink bandwidth on an unnecessarily high audio bitrate when you can use it for more meaningful telemetry?

Who says it's wasted? They have the bandwidth available to use if they wanted to.
Chuck - DIRECT co-founder
I started my career on the Saturn-V F-1A engine

Offline SWGlassPit

  • I break space hardware
  • Full Member
  • ****
  • Posts: 437
  • Liked: 249
  • Likes Given: 35
Re: Basic Rocket Science Q & A
« Reply #951 on: 09/09/2014 03:37 PM »
If the current voice communication is adequate, would you rather use an additional, say, 128 kbps, to make that voice silky smooth, or would you rather use it for systems monitoring?  Keep in mind, also, that ISS isn't the only TDRS customer.

Offline breadfan

  • Member
  • Posts: 25
  • Liked: 7
  • Likes Given: 31
Re: Basic Rocket Science Q & A
« Reply #952 on: 09/20/2014 05:18 AM »
Realistically, how likely is it that an anomaly will occur due to launching in inclement weather?
Is it realistic that future LV's will be capable of flying all but the most intense weather, just like all other forms of transport? Seems like a necessary development if SF is to become as routine as other regular flight in the future, given how often weather causes delays.

Offline QuantumG

  • Senior Member
  • *****
  • Posts: 8093
  • Australia
  • Liked: 2863
  • Likes Given: 685
Re: Basic Rocket Science Q & A
« Reply #953 on: 09/20/2014 05:22 AM »
Seems kinda like the opposite, the Saturn V and the old reliable Soyuz have happily launched in terrible weather, but these new launch vehicles don't.
Jeff Bezos has billions to spend on rockets and can go at whatever pace he likes! Wow! What pace is he going at? Well... have you heard of Zeno's paradox?

Offline breadfan

  • Member
  • Posts: 25
  • Liked: 7
  • Likes Given: 31
Re: Basic Rocket Science Q & A
« Reply #954 on: 09/20/2014 05:28 AM »
Of course, there was the whole lightning strike and SCE-to-AUX episode.

Offline Jim

  • Night Gator
  • Senior Member
  • *****
  • Posts: 31222
  • Cape Canaveral Spaceport
  • Liked: 9494
  • Likes Given: 298
Re: Basic Rocket Science Q & A
« Reply #955 on: 09/20/2014 08:29 PM »
Realistically, how likely is it that an anomaly will occur due to launching in inclement weather?
Is it realistic that future LV's will be capable of flying all but the most intense weather, just like all other forms of transport? Seems like a necessary development if SF is to become as routine as other regular flight in the future, given how often weather causes delays.

Spacecraft don't like it.

Offline Avron

  • Canadian Member
  • Senior Member
  • *****
  • Posts: 4915
  • Liked: 147
  • Likes Given: 150
Re: Basic Rocket Science Q & A
« Reply #956 on: 09/20/2014 08:56 PM »
Seems kinda like the opposite, the Saturn V and the old reliable Soyuz have happily launched in terrible weather, but these new launch vehicles don't.


so much for progress

Online ugordan

  • Senior Member
  • *****
  • Posts: 7334
    • My mainly Cassini image gallery
  • Liked: 1501
  • Likes Given: 320
Re: Basic Rocket Science Q & A
« Reply #957 on: 09/20/2014 09:09 PM »
Seems kinda like the opposite, the Saturn V and the old reliable Soyuz have happily launched in terrible weather, but these new launch vehicles don't.


so much for progress

Again, look up Apollo 12 for a weather lesson.

Offline Avron

  • Canadian Member
  • Senior Member
  • *****
  • Posts: 4915
  • Liked: 147
  • Likes Given: 150
Re: Basic Rocket Science Q & A
« Reply #958 on: 09/20/2014 09:11 PM »
Seems kinda like the opposite, the Saturn V and the old reliable Soyuz have happily launched in terrible weather, but these new launch vehicles don't.


so much for progress

Again, look up Apollo 12 for a weather lesson.

Sometimes things get pushed a little far.. still they all made it..

Online ugordan

  • Senior Member
  • *****
  • Posts: 7334
    • My mainly Cassini image gallery
  • Liked: 1501
  • Likes Given: 320
Re: Basic Rocket Science Q & A
« Reply #959 on: 09/20/2014 09:12 PM »
Seems kinda like the opposite, the Saturn V and the old reliable Soyuz have happily launched in terrible weather, but these new launch vehicles don't.


so much for progress

Again, look up Apollo 12 for a weather lesson.

Sometimes things get pushed a little far.. still they all made it..

Is that what you tell your customer when his payload, for a change, *doesn't* make it?

"Sorry, we pushed it a little too far."

Seriously...
« Last Edit: 09/20/2014 09:15 PM by ugordan »