Much has been made of the fact that, for want of software, Dragon could have saved itself and its payload.It just occurred to me that as of soon (now?) the first stage is also a valuable piece of hardware that could potentially save itself in the event of a second stage failure.
Quote from: mikelepage on 07/31/2015 10:20 amMuch has been made of the fact that, for want of software, Dragon could have saved itself and its payload.It just occurred to me that as of soon (now?) the first stage is also a valuable piece of hardware that could potentially save itself in the event of a second stage failure.A lot of discussions on this site are like this, asking if something can be done, then going through the details of how to do it. But good engineers should also look at the cost/benefit analysis. What's the bang-for-buck here?For Dragon, its obvious. They're already working on the abort software for Dragon 2. Applying that to Dragon 1 won't require much additional development. And since the CRS-7 Dragon was carrying some expensive hardware, the bang-for-buck to software upgrade Dragon 1 is a no-brainier.But for the first stage, bang-for-buck is much less obvious. First, think about how many times something like CRS-7 will reoccur. Assuming SpaceX fixes the underlying problem with the seconds stage, it may not reoccur at all. But for the sake of discussion, let's say CRS-7 type events do reoccur, perhaps once every 5 years. For me, this seems highly improbable, but let's run with it. If the first stage costs around $30 million, that would be a cost of 6 million a year. So that would be the benefit: maybe $6M/year max. ...
I don't think that the Dragon 2 abort software has anything to do with the Dragon 1 deploying parachutes. Dragon 2 abort software is way more complicated then what Dragon 1 "needs". Dragon 1 just needs to be able to:1. Arm deploying the drogue (that should never be possible by default on ascent.)2. Deploy the drogue.Maybe it needs to disconnect from the trunk, maybe it can "lawn dart" or tumble until the drogue deploys. That's it. It may be commanded rather then automated because the simpler the better.
The software to initiate the parachute deployment was not in Dragon 1. It certainly was planned for Dragon version 2, and one of the things we've decided to do is to advance the software that was meant for Dragon version 2 into Dragon version 1 so that if something like this were to happen in the future, the Dragon spacecraft would save itself.
Quote from: mme on 08/11/2015 09:04 pmI don't think that the Dragon 2 abort software has anything to do with the Dragon 1 deploying parachutes. Dragon 2 abort software is way more complicated then what Dragon 1 "needs". Dragon 1 just needs to be able to:1. Arm deploying the drogue (that should never be possible by default on ascent.)2. Deploy the drogue.Maybe it needs to disconnect from the trunk, maybe it can "lawn dart" or tumble until the drogue deploys. That's it. It may be commanded rather then automated because the simpler the better.Yeah, I could have phrased that better. Here's how Elon says it:QuoteThe software to initiate the parachute deployment was not in Dragon 1. It certainly was planned for Dragon version 2, and one of the things we've decided to do is to advance the software that was meant for Dragon version 2 into Dragon version 1 so that if something like this were to happen in the future, the Dragon spacecraft would save itself.http://shitelonsays.com/transcript/elon-musk-talks-failed-crs-7-dragon-mission-2015-07-20Obviously Dragon v1 already knows how to land using parachutes. That's how all Dragons have landed so far, from COTS-1 through CRS-6. But until now, Dragon v1 didn't know how to use parachutes on an abort, which is why CRS-7 Dragon was lost.If Dragon v2 aborts, it will use parachutes to land. Yes, a Dragon v2 abort involves much more than this, but the bit of software that deploys parachutes on a Dragon v2 abort can be applied to Dragon v1.
That brings up a question: Are D1 spacecraft also equipped with flight termination charges?
That brings up a question: Are D1 spacecraft also equipped with flight termination charges? In a similar mishap where the D1 separates and the parachutes do not deploy, I'd hate to see this kind of Dragon eat people or property from an uncontrolled fall.