Author Topic: Sierra Space Dream Chaser DISCUSSION Thread (was SNC)  (Read 1064672 times)

Offline intrepidpursuit

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Re: Sierra Space Dream Chaser DISCUSSION Thread (was SNC)
« Reply #1820 on: 07/27/2017 09:41 pm »
This has probably been discussed before but is there any reasons that DC could not fly to cislunar space?

I remember that SNC's original plans was that DC could fly to BLEO but some time after that, they changed their mind and said that DC was LEO only.

But my question is more whether it would be difficult to adapt DC for BLEO since NASA said that it will need cargo services to the DSG.

With the cargo module is has more space and has solar panels, so it would seem that in theory it could. There is more to loiter time than just solar panels, but the cargo section would seem to afford them some more design freedom then keeping everything inside the OML.

Offline brickmack

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Re: Sierra Space Dream Chaser DISCUSSION Thread (was SNC)
« Reply #1821 on: 07/27/2017 10:54 pm »
With the cargo module is has more space and has solar panels, so it would seem that in theory it could. There is more to loiter time than just solar panels, but the cargo section would seem to afford them some more design freedom then keeping everything inside the OML.

Internal volume isn't really a time issue, just affects the number of flights needed to deliver a certain cargo amount. It would be helpful for a crew flight, but I don't think the current expansion module concept is very applicable there (requires a fairing which inhibits an abort), if they needed extra space on a crew mission they'd probably build a pressure vessel into the boattail instead. And needing a fairing also means the wings have to fold up, which could be a much bigger safety issue on high-speed reentries (I kinda doubt even the crew variant could survive that, so lets not put extra failure points in). As for solar panels, SNC has previously presented solar array concepts that would deploy from the rear of the spaceplane itself, or from a much smaller expendable module. And with the greater delta v requirements for a NRHO or LDRO mission, mass isn't something they have available to waste anyway. I think the extra module is probably either neutral or a net negative for a cislunar variant

Offline Khadgars

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Re: Sierra Space Dream Chaser DISCUSSION Thread (was SNC)
« Reply #1822 on: 07/27/2017 11:20 pm »
This has probably been discussed before but is there any reasons that DC could not fly to cislunar space?

I remember that SNC's original plans was that DC could fly to BLEO but some time after that, they changed their mind and said that DC was LEO only.

But my question is more whether it would be difficult to adapt DC for BLEO since NASA said that it will need cargo services to the DSG.

I don't believe it could withstand re-entry coming from the moon.
Evil triumphs when good men do nothing - Thomas Jefferson

Offline CameronD

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Re: Sierra Space Dream Chaser DISCUSSION Thread (was SNC)
« Reply #1823 on: 07/28/2017 01:17 am »
This has probably been discussed before but is there any reasons that DC could not fly to cislunar space?

I remember that SNC's original plans was that DC could fly to BLEO but some time after that, they changed their mind and said that DC was LEO only.

But my question is more whether it would be difficult to adapt DC for BLEO since NASA said that it will need cargo services to the DSG.

I don't believe it could withstand re-entry coming from the moon.

Well, they can make it to orbit in the movie theatre:  ;D



https://en.wikipedia.org/wiki/The_Space_Between_Us_(film)


« Last Edit: 07/28/2017 01:19 am by CameronD »
With sufficient thrust, pigs fly just fine - however, this is not necessarily a good idea. It is hard to be sure where they are
going to land, and it could be dangerous sitting under them as they fly overhead.

Offline Patchouli

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Re: Sierra Space Dream Chaser DISCUSSION Thread (was SNC)
« Reply #1824 on: 07/31/2017 08:02 pm »
This has probably been discussed before but is there any reasons that DC could not fly to cislunar space?

I remember that SNC's original plans was that DC could fly to BLEO but some time after that, they changed their mind and said that DC was LEO only.

But my question is more whether it would be difficult to adapt DC for BLEO since NASA said that it will need cargo services to the DSG.

I don't believe it could withstand re-entry coming from the moon.

I remember reading it would need a couple of hundred pounds of ablative added to the hottest parts and a skip reentry used.
A BLEO variant probably would need other changes such as much more delta V to be able to perform any useful missions.
This likely would mean changing everything inside around which would make it effectively a new vehicle or adding a full service module which would be big development program in it's own right.

Well, they can make it to orbit in the movie theatre:  ;D



https://en.wikipedia.org/wiki/The_Space_Between_Us_(film)




I think it also showed up in a cut scene in the Martian.
Not sure why they cut it out.
« Last Edit: 07/31/2017 08:14 pm by Patchouli »

Offline dwheeler

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Re: Sierra Space Dream Chaser DISCUSSION Thread (was SNC)
« Reply #1825 on: 08/25/2017 05:33 pm »


I guess I don't hate that stupid nose skid as much after having seen this. Still not luvin' it though...  :D

Does anyone know if it provides any directional steering capability during the landing roll? Or are they planning on differential braking? Or something else?

Moving my above post from the UPDATE thread. Question still stands if anyone has any information about it...

Offline Jeff Lerner

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Re: Sierra Space Dream Chaser DISCUSSION Thread (was SNC)
« Reply #1826 on: 08/26/2017 02:29 am »
On landing if a tire blows on one of the rear wheels does having a nose skid vs. A steerable nose wheel help or hinder controlling the rollout ??

Offline Rocket Science

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Re: Sierra Space Dream Chaser DISCUSSION Thread (was SNC)
« Reply #1827 on: 08/28/2017 02:03 am »
On landing if a tire blows on one of the rear wheels does having a nose skid vs. A steerable nose wheel help or hinder controlling the rollout ??
If the tire loses pressure before landing the technique is to land with weight on the good tire using aero control surfaces until the airspeed bleeds of and allow the the tire to contact the ground then use opposite side braking to compensate for the drag from the deflated tire. If a tire blows on contact you still use aero control surfaces until they lose effectiveness and with opposite braking...
« Last Edit: 08/28/2017 02:03 am by Rocket Science »
"The laws of physics are unforgiving"
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Offline CameronD

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Re: Sierra Space Dream Chaser DISCUSSION Thread (was SNC)
« Reply #1828 on: 08/28/2017 06:33 am »
On landing if a tire blows on one of the rear wheels does having a nose skid vs. A steerable nose wheel help or hinder controlling the rollout ??
If the tire loses pressure before landing the technique is to land with weight on the good tire using aero control surfaces until the airspeed bleeds of and allow the the tire to contact the ground then use opposite side braking to compensate for the drag from the deflated tire. If a tire blows on contact you still use aero control surfaces until they lose effectiveness and with opposite braking...

Perhaps the point is that you can't blow out a nose skid?...
With sufficient thrust, pigs fly just fine - however, this is not necessarily a good idea. It is hard to be sure where they are
going to land, and it could be dangerous sitting under them as they fly overhead.

Offline Rocket Science

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Re: Sierra Space Dream Chaser DISCUSSION Thread (was SNC)
« Reply #1829 on: 08/28/2017 01:40 pm »
On landing if a tire blows on one of the rear wheels does having a nose skid vs. A steerable nose wheel help or hinder controlling the rollout ??
If the tire loses pressure before landing the technique is to land with weight on the good tire using aero control surfaces until the airspeed bleeds of and allow the the tire to contact the ground then use opposite side braking to compensate for the drag from the deflated tire. If a tire blows on contact you still use aero control surfaces until they lose effectiveness and with opposite braking...

Perhaps the point is that you can't blow out a nose skid?...
I read the question as he asked does a "steerable nose wheel help or hinder controlling the rollout ??"  My opinion is that it doesn't come much into play as the drag from the mains is greater and control should suffice with minimal off center line excursion as the vehicle is equipped...
"The laws of physics are unforgiving"
~Rob: Physics instructor, Aviator

Offline Rocket Science

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Re: Sierra Space Dream Chaser DISCUSSION Thread (was SNC)
« Reply #1830 on: 08/28/2017 07:44 pm »
Starting to feel that Dream Chaser "mojo" again... 8) Thanks for the great update article Chris G! :)
"The laws of physics are unforgiving"
~Rob: Physics instructor, Aviator

Offline rayleighscatter

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Re: Sierra Space Dream Chaser DISCUSSION Thread (was SNC)
« Reply #1831 on: 08/28/2017 08:31 pm »
It's certainly not an area I claim to be an expert in but I understand that nose wheel steering in general isn't used at higher speeds (such as landing or takeoff), it's mostly used for taxiing. Steering at higher speeds is done through differential braking or with aerosurfaces. It's even considered enough of a hazard that most aircraft that have it won't allow nose wheel steering to engage above certain speeds, or if it does it only permits a few degrees of movement (something less than 7 degrees, very minimal).

So it's probably mostly a non-issue as the nose shouldn't be steering at high speeds.

Offline adrianwyard

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Re: Sierra Space Dream Chaser DISCUSSION Thread (was SNC)
« Reply #1832 on: 08/28/2017 08:58 pm »
Another point of reference: Virgin Galactic evidently believe the same configuration is a suitable for frequent tourist flights , i.e. a winged vehicle with a nose skid and aero-surface / differential main-grear brake-steering.

Offline Rocket Science

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Re: Sierra Space Dream Chaser DISCUSSION Thread (was SNC)
« Reply #1833 on: 08/28/2017 09:18 pm »
It's certainly not an area I claim to be an expert in but I understand that nose wheel steering in general isn't used at higher speeds (such as landing or takeoff), it's mostly used for taxiing. Steering at higher speeds is done through differential braking or with aerosurfaces. It's even considered enough of a hazard that most aircraft that have it won't allow nose wheel steering to engage above certain speeds, or if it does it only permits a few degrees of movement (something less than 7 degrees, very minimal).

So it's probably mostly a non-issue as the nose shouldn't be steering at high speeds.
To add, some light aircraft don't even have nose wheel steering and it is free to caster...
"The laws of physics are unforgiving"
~Rob: Physics instructor, Aviator

Offline punder

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Re: Sierra Space Dream Chaser DISCUSSION Thread (was SNC)
« Reply #1834 on: 08/28/2017 09:43 pm »
To add, some light aircraft don't even have nose wheel steering and it is free to caster...

IIRC even some Soviet jet fighters used castering nose wheels, presumably to cut down on weight and complexity.

I learned to fly in an airplane with a castering nose wheel. You get used to it, but it's still a pain vs. a steering nose wheel.

Offline CameronD

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Re: Sierra Space Dream Chaser DISCUSSION Thread (was SNC)
« Reply #1835 on: 08/28/2017 11:04 pm »
To add, some light aircraft don't even have nose wheel steering and it is free to caster...

IIRC even some Soviet jet fighters used castering nose wheels, presumably to cut down on weight and complexity.

I learned to fly in an airplane with a castering nose wheel. You get used to it, but it's still a pain vs. a steering nose wheel.

It's been explained to me during pilot training that stationary rubber hitting the tarmac at high speed melts resulting in a situation akin to aquaplaning.  Allowed to continue, the tyre will heat up and burst and a bust nose-wheel is going to result in quite a lot of damage to both the aircraft and the runway.  It's for this reason castering nose wheels were seen as a good idea - the nose wheel is always going to track in the direction the aircraft is going, no matter what the pilot is trying to do.

 
With sufficient thrust, pigs fly just fine - however, this is not necessarily a good idea. It is hard to be sure where they are
going to land, and it could be dangerous sitting under them as they fly overhead.

Offline TomH

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Re: Sierra Space Dream Chaser DISCUSSION Thread (was SNC)
« Reply #1836 on: 08/29/2017 04:56 am »
Some questions:

Is ULA signed up for Atlas V to launch all 6 of their CRS 2 launches, or is there any chance at all they'd pay less for SpaceX to launch it? And would SX be willing to do that?

After the chopper drops, is there any chance now of higher test drops from the STS Carrier aircraft, Stratolaunch, or White Knight 2 before launch to LEO? I know White Knight 2 drops were cancelled for the manned version, but years have now passed.

As far as this Hubble Servicing Mission mentioned in the article, I presume it would be limited to prop delivery, with no swap out of large components? Canada arm is probably vastly too big isn't it? Could it be cut down in size? Is any of the other servicing gear from STS missions still around and if so, could it be used from this much smaller craft? Surely some qual flights would be required before any Hubble servicing mission would be approved. Can Hubble last until that happens?
« Last Edit: 08/29/2017 05:05 am by TomH »

Offline Steven Pietrobon

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Re: Sierra Space Dream Chaser DISCUSSION Thread (was SNC)
« Reply #1837 on: 08/29/2017 07:43 am »
As far as this Hubble Servicing Mission mentioned in the article, I presume it would be limited to prop delivery, with no swap out of large components?

Hubble doesn't use propellant, as it would contaminate the mirror. The mission might be just to boost the orbit and add a deorbit motor. I would think changing out parts and instruments would be difficult for an uncrewed mission.
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline woods170

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Re: Sierra Space Dream Chaser DISCUSSION Thread (was SNC)
« Reply #1838 on: 08/29/2017 07:49 am »
As far as this Hubble Servicing Mission mentioned in the article, I presume it would be limited to prop delivery, with no swap out of large components?

Hubble doesn't use propellant, as it would contaminate the mirror. The mission might be just to boost the orbit and add a deorbit motor. I would think changing out parts and instruments would be difficult for an uncrewed mission.
Replace "difficult" with "impossible".

Offline Tomness

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Re: Sierra Space Dream Chaser DISCUSSION Thread (was SNC)
« Reply #1839 on: 08/29/2017 12:36 pm »
Will Dream Chaser have to do a demonstration mission like SpaceX's COTS 2+ and Orbital ATK's Orb-D1 before operational missions?

 

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