Friday, November 30, 2007

ITER Control

Emerging Technologies takes a look at ITER control and safety systems. They plan to sample at 5 MHZ for data acquisition.

Here is a nice pdf to get you started.

Sunday, November 18, 2007

Vacuum Pumping



Adixen - Mag Lev [pdf]
Pfeiffer - Mag Lev
Varian [pdf]


Turbo Molecular Pump Comparison
H2 Speed l/sH2 Compression Ratio
Adixen ATH-2300M12003.0X103
Pfeiffer HiMag 340028504X104
VarianTurbo V 3K-T23001.5X104

It looks like the Pfeiffer HiMag 3400 all the way.




Update 21 Nov 007 0642z



Corrected in the text.

Friday, November 16, 2007

Data Collection

Dr. Bussard in his lab notes says that the ionization and other quick gas processes happen in 1 to 2 microseconds. Nyquist says that to be sure of capturing the highest frequency of interest you have to sample at 2X that frequency. Even so, if you sample at the zero crossings you will miss it. So much for Nyquist.

What we want is not just to measure process completions, but also look at what is happening in those processes. We might gain some insights. To do that you have to sample at least 3X the frequency of interest and much better 20X.

That says we need to sample at 20 MSPS. Front your sampler with a nice high speed fiber optic transimpedance amplifier in parallel with a DC (relatively) amplifier for low frequency fidelity and you have a very nice front end for a lot of the instrumentation we will need.

Stuff that will be sampled less frequently can of course use a much less expensive design.

With memory as cheap as it is these days I think that you decide what your maximum data collection time is at high speed and keep that amount of memory local. Then you have some kind of stupid simple protocol (say RS-485 as the physical layer) to collect the data. 5 MBPS shouldn't be too tough. With a 60% efficient protocol you should be able to collect the data from 1 high speed channel in 100 seconds. About 2 minutes. Twenty such channels in under 35 minutes. If you used 100 Base T Ethernet in a command-response type network you should get transmission time to come it at around 3 1/2 minutes. The slower RS-485 might be better if you have to collect data in an operational situation. Command-response Ethernet in relatively quieter environments (do a shot - recharge everything - hit it again).

Of course to see what the actual timings are like you have to pass around a synchronizing signal. Getting everything to start within 10% of the actual start time means passing out nice pulses on cables that differ in length from each other by no more than 20 inches. Not too tough.

Update: 31 May 008 0337z


Gas Valve Design




It also looks like we will need a multi stage regulator. 20 psia (5 psig) to 5 torr. 5 torr to 1E-3 torr. And the final control stage of 1E-3 torr to 1E-7 torr. Individual stages for the experimental reactor should be able to vary pressures over at least a 10 to 1 range (100 to 1 is better) to account for required gas flow variations depending on operating pressure. Once we understand operation better we can optimize for actual flow requirements.

It looks like piezo electric benders are not going to work since the travel is much too small. Something on the order of 1 to 2 micro meters. What we need is something better. A voice coil motor. That can easily give +/- 30 thousandths of an inch travel. It has a drawback in that it is magnetic in nature and thus can't be placed inside the the magnetically shielded grids. For small reactors a 2 ft length tube will add about 2 mS delay to the control system. Not good. Not insurmountable.

As the reactors increase in size delay will go up linearly with size. This is bad. Volume will go up as the cube of size. This is good. More volume reduces the need for fast control.

In fact the whole gas system may need a number of reservoirs to make the control problems tractable. It is pretty much a truism in business these days that the faster the manufacturing system can respond to demand the smaller the required inventory. So it is with any control system. We will adjust our inventories accordingly.

Turbo Pump Ratings

An education is a wonderful thing. I'm getting an education. I hope to distill it into a couple of useful paragraphs.

Turbo molecular pumps (TMPs) are rated for gas flow at a certain chamber pressure. A high volume pump I am looking at is rated at 2,000 liters a second. How many ccs a second is that at STP (not Space-Time Productions - Standard Pressure and Temperature, which is 760 torr and 273.15°K) at a chamber pressure of 1E-7 torr?

2,000 l/s * 1,000 cc/l * 1E-7 torr * 1 atm/760 torr = 2.63E-4 cc/sec @ STP

Turbo pumps have a compression ratio rating. Let us look at what that means in terms of ultimate chamber pressure in terms of the worst case gas - molecular Hydrogen. The particular pump I am looking at is rated at an ultimate pressure (on the low side) of 1E-9 torr. If the pump has a compression ratio of 10,000 for hydrogen that means the outlet of the TMP must be held at a pressure of 1E-5 torr to reach a final pressure of 1E-9 torr.

We leave the design of an actual system as an exercise for the reader. Dig out them catalogs and get the slide rules slipin.

Thursday, November 15, 2007


I have been giving some thoughts to ionization gauges lately in terms of pressure control. What if we used one without a filament to detect ions? Put it in line with a beam path but out of the way of the beam so it doesn't become an added loss mechanism and see if you get a good signal. Bursts of high energy Heliums.

There will be problems. High energy Helium ions are going to be a heating problem. Secondary ionizations will be a problem. If the bias voltage needs to be in the MV range that will be a problem.

Still, I think something useful could be worked out. Low power test reactors can probably get by with some high temperature wire. For higher powers we may need to think of something else. By then of course we ought to know a lot more and the solution will be obvious.

Wednesday, November 14, 2007

Ionization Pressure Guages

In my effort to map out a control strategy for reactor pressure control I have been studying ionization gauges. Depending on cathode emission and plate voltage they are very linear. Given their construction and plate voltage (in the 200 to 350 volt range) their response speed should be at least in the low MHz range.

The limiting factor is going to be the current amplifier (because current is proportional to gas density). At low currents - current amplifiers tend to have low bandwidths. Should that be a problem in controlling the reactor the gauge operating conditions could be optimized for the desired control range. A second gauge operated normally could be used to turn off the gauge if pressures got too far out of range. That should give us a readout bandwidth in the 100s of KHz.

With a valve bandwidth of 1,000 Hz and a reactor fill time of 1 second with a full open control valve, pressure control to within 1% ought to be easy. A little work could bring that in to .5%. Dr. B. said that his suggested pressure was 1E-7 torr because his control system was lousy. He said the real number was about 30X higher. If that is the case an increase of density with better control should allow at least a 10X increase in pressure. For D-D that means a reactivity increase of n2/2 - about 50X. If we could keep things tight enough to get the whole 30X increase in pressure it would give a gain improvement of 450. Tight pressure control is one of the critical keys to making this work.

You can get a nice first pass of ionization gauge theory and practice from this page. Click on Introduction to Bayard-Alpert Gauges. It will bring up a [pdf] "open or save" block.

Which has got me to thinking. If POPS causes density waves in the plasma and those density waves get coupled to the neutrals it may be possible to use an ionization gauge to measure POPS frequencies. You would use a diplexer. The low frequency signals would go to the pressure controller and the high frequency signals would feed the POPS frequency controller phase detector (after suitable division if required).

BTW if you are going to use CMOS I used to highly recommend the Philips 74HC4046 however Philips is no longer in the Semiconductor business. Instead that business is now called NXP. So here is NXP version of the 74HC/HCT4046A[pdf]

Thinking About Control

I keep thinking about test reactor control issues - things that need controlling, signals to use for control. I want to leave off things like cooling and other secondary functions which are quite important but are easily controlled and instrumented and happen on relatively long time scales.

Reactor controls are going to be a bitch. Let me run down the list of what needs controlling, some of the interactions and what signals we can use for feedback. This will be in relation to a test reactor about 1 meter across in total dimensions designed for continuous operation burning D-D.

1. Anode (called a grid in the Bussard Reactor) HV
2. POPS frequency, POPS voltage (added to Anode DC)
3. Gas Pressure
4. Electron Injection

Controlling the pumping speed of the turbo pumps is an option but that is rather slow and need only be done to set the base gas flow from the gas pressure controller. We could also vary the magnet current, but again that is slow and is relatively easy to do a set and forget based on the well voltage and the system geometry. So that sets out what we have for plant controls.

What kind of feedback signals can we get?

1. Neutrons - they tell us the fusion rate.
2. Light (PMT amplified) - electron density.
3. X-Ray output with energy binning - who knows what we might learn
4. High Energy Alpha Output - fusion rate
5. Pressure gauges - gas flow
6. High Frequency Current Transformer in the Anode Circuit Ground - you can learn a lot by watching

Burning D-D simplifies things. So far as we know there are no peaky resonance regions in the curve so we don't need to figure out how to keep the reactor anode voltage at some process determined level. So that is one complication out of the way. Second off we can use a high vacuum pressure gauge with out worrying about readings being gas composition dependent.

So we have pressure control. From a quick look at what is out there in terms of pressure measuring equipment it looks like ten measurements a second is a reasonable rate. That means that we probably will have a first order roll off on the loop of about 1 second. That is not too bad as the way the system works helps us. If it takes a certain time T to reach a given pressure it takes 10T to get to 10 times the pressure. Given that fact and the fact that the flow is initially designed to fill the reactor in 1 second control within a 2 to 1 range ( from .6 times the set point to 1.5 times the set point) should be easy. Tighter control of course would be better. We should try to get faster updates from the pressure measuring eqpt. Or we could opt for lower flow from the gas delivery system. Since most of the flow rate will be determined by the capacity of the turbo molecular pumps we could also go for a flow system calibrated to deliver 80% of the required flow and then just have a variable valve to make up the difference.

So gas density should be another set and forget.

That really leaves us only one thing that needs to be controlled on the fly. POPS frequency. Since we plan on impressing it on the Anode the anode current would not be a good place to read it out. If we used an antenna inside the reactor it would have the same problem. What we need is a signal read out that is independent of moving charges. The most likely signal for that is either the X-ray detector or the neutron detector. Since POPS for a drive voltage of 50 KV is expected to be in the 2 to 30 MHz range we will need a neutron measurement or X-Ray measurement system that can give us output at those frequencies. Also the detector efficiency should be such that it can detect at least .3E9 photons or neutrons a second if we are to reliably detect 30MHz. That will be tough. POPS experiments may need to be done with a sweep generator without feedback on small reactors.

Ideally if enough alphas are generated it should be possible to turn off the electron guns and just use the electrons left behind by the fusion alphas as the electron source. Of course if the electron guns must be left on they could be modulated at the POPS frequency and read out could come from the Anode ground current, considerably simplifying matters. The light output (PMT Amplified) could be used as a signal to throttle back the electron guns.

However, we really do not want continuously operating electron guns in a power reactor except for startup. They get in the way mechanically unless they can be placed on the walls of the reactor.

Tuesday, November 13, 2007

Orifice Sizing

I have been mulling over the flow control problem for a small test reactor and I think I have at least a partial solution. First lets lay out the dimensions of the problem. Let us say that the reactor is a sphere with a diameter of .9 meter and a core diameter of .3 meter. The volume of a sphere is 4/3 π r3. A fair approximation for our work is 4 r3. So the volume of the outer sphere is 4 * (.45)3 = .36 m3. Minus the inner volume of 4 * (.15)3 = .014 m3 hardly worth worying about. So we won't. So we are at about .35E6 cm3 for volume.

Now how about pressure. We want to keep the pressure in that volume below 1E-7 torr. What is that in atmospheres? To help us along we have a handy pressure calculator. The answer is 1.3E-10 atmosphere. Times .35E6 cc. So it takes about 5E-5 cc at STP to fill the chamber.

Now it turns out that there is a dandy orifice company called Lenox Laser who appear to have just what we need. An orifice calculator. Let us set it up to fill our tank in one second. That should give us pressure control of better than 1% if we can get our valve to go from on to off in a millisecond. So we start with an inlet pressure of 1 torr to our control valve. The other side of the orifice will be at chamber pressure. 1E-7 torr. Since we are figuring this for Deuterium we will use He4 as a substitute for 2H2 (a Deuterium molecule). Use 273.15 Kelvin for the gas temperature. A flow rate of 5E-5 cc/sec. And we have an answer. 9.7 microns. Say 10 to make it even. A small orifice. Not the smallest (they go down to 1 micron).

From their catalog [pdf] you can scroll down to page 28 and find a nice 10 micron orifice that is drilled into a 1/4-28 set screw for under $100 bucks. Or if you get a disc from page 3 under $35.

Now of course we haven't taken into account any gas the turbo pumps are taking out or that is being burned up as the Deuteriums fuse (a minuscule amount) but at least we know what ball park we are in and at the lowest flow we are likely to want we can do the job. Now for that 1 torr regulator.

Update 1924z 19 Nov 007

We can look at some turbo pump estimates. Let us suppose we have 6 turbo pumps each capable of 3,000 l/s pumping speed. How much flow would be required? Let us look at the low end. That would be 18,000 l/sec or 1.8E6 cc/sec. If we start at 1E-7 torr that would be about .24E-3 cc/sec at STP. I have decided to have an intermediate regulator to get the gas pressure down to 1E-3 torr to the final regulator.

So what hole sizes do we need? Let us start with our original

Inlet to Outlet
1E-3 to 1E-7 torr 5.0E-5 cc/sec 40 microns

1E-3 to 1E-8 torr 2.4E-5 cc/sec   28 microns
1E-3 to 1E-7 torr 2.4E-4 cc/sec   87 microns
1E-3 to 1E-6 torr 2.4E-3 cc/sec 275 microns
1E-3 to 1E-5 torr 2.4E-2 cc/sec 870 microns

Saturday, November 10, 2007

PID Loops And Leak Valves

PID Loops (Proportional, Integral, Differential) are probably the most common kind of control loops in existence. They are easy to set up. If you do them in software they are easy to code. Plus they are fairly robust to changes in the environment. Good stuff.

This all came up as a topic of discussion during a look at what it might take to maintain a constant pressure in a Bussard Test Reactor that had coils about 1/3rd of a meter across. Here is some of the discussion from my side with some corrections and updates:

I'm not familiar with controlled leak valves. (I am more familiar than I was - Controllead Leak Valve). If they are ON/OFF type valves you may be able to get better control of low rates by using 5 or 8 valves in a 1-2-4-8- flow sequence. Kind of a gas flow D to A converter. If you then have a pressure regulator up stream to control the gross flow rates that might be all the flow control you need.

Or it may be way more than you need.

A rough estimate of your needs can be figured by calculating the allowable delta P vs delta T. (pressure vs time). Looking at the volumes involved. The gas dead space in the valve. Valve reaction time. Pumping speed. etc. to find out what ball park you have to play in.

I can help with PID loops (at least at the pseudo code level - actual coding if you use FORTH) if that would do you any good. The main thing is to reduce dead times as much as possible (esp time from valve close signal to flow <10% of open valve flow - or if it is a proportional valve to 10% of its last programmed rate. Same when going from off to on except the relevant number is 90%.). You also have to consider measurement delay including gas diffusion time. It may be that reactors below a certain size are not practical for continuous operation.

Your gas pressure measurement should be as close to the valve as reasonably possible. We can compensate for initial over measurement (i.e peak higher than final value), what is harder to compensate for is the loss of time.

BTW if you code your own loops use the form the Chemical Industry folks use where everything is in terms of overall gain and time parameters. It will simplify your tuning job. Disturbance response tuning is a nice simple way to get into the ball park. Or ask me. We can even make it auto-tune if you like.

Controller output = K ( e + Σe*Δt/Ti + Td*Δe/Δt) where K is gain, e is error from set point Ti is integration time and Td is derivative time and t is just time.

Setting the loop is simple. You input a small step in your process. The slope of the first order response determines you gain K. The dead time determines Ti. Td is 1/10th Ti. In noisy processes Td will make things worse and should be set to zero.

Of course you could do it with independent gains for each term, but that doesn't give you the reality connection thinking about overall gain and time does.

Update: The Step Response method is called the Cohen Coon Tuning Method. Here is one method for using it. None of the numbers used is etched in stone. They represent a particular type of filter operating within a particular frequency range. A more aggressive response with its attendant twitchiness may be just what you want. Or you might wish for a gentler response - easy does it.

BTW with respect to the above method I like to get my response times and amplitudes from the 20% point to the 30% point of ultimate response. Things are pretty linear in that area so no need to resort to natural logs in the calculations. Which is kind of handy if the computing must be done within a short time in a limited memory microprocessor. In any case with PID pretty close is often all that is required to be pretty good. The only time a real plant will operate exactly the same way every time is when it is generated from a formula. In fact the integrator is required because plant resistance to change varies - with time, operating point, settings on other plant controls, wind, rain, sunshine and sun spot cycles. Gain gets you close. Integration zeros out the residual error. Differential prevents you from coming in to the final value too hot. It also helps when the error is getting bigger.

Here is a plant simulator that is some fun to play with.

Wiki is pretty good on PID. When you get down to the bottom they do a good job of relating theoretical PID loop mathematics to useful PID loop mathematics. As far as I know the motor control guys still like the theoretical math and the chemical plant guys like the practical math. I'm a motor guy, but my vote on the subject is with the Chemical Plant control guys.

Friday, November 9, 2007

Research Speed

One way to keep things moving along at a good clip is to do things in parallel. When it is done on a computer chip it is called pipelining.

So here is one way to pipeline the research.

Every test reactor station has one set of power supplies. It should have 3 reactors so that:

1. One is operational for testing.
2. One is being modified.
3. One is cooking out preparatory to testing.

Testing then can go on almost continuously.

Since the power supplies are the major cost driver for a test set up designed for continuous operation, and because the supplies will not change much with time, sharing the supplies with three nearly identical reactors should give a significant time advantage without much added cost. In fact cost per hour of use will decline with more intensive use since you are paying for less idle time.

Wednesday, November 7, 2007

Burning Pu And Other Stuff









Monday, November 5, 2007

WB6 Lab Notes Added

To the Fusion Resources area of the sidebar.

Thanks to John P. at Talk Polywell.

A Suppliers List has been added to the Sidebar.

Update: 31 May 008 0337z


Sunday, November 4, 2007

We Had Better Get A Move On

There is a very interesting discussion of the nuclear proliferation aspects of the Bussard Fusion Reactor going on at Talk.Polywell. Here is what I think needs to be done:

We need to build Bussard Reactor neutron generators as soon as possible to test out possible proliferation aspects - like trying to make Plutonium - so we can figure out the best ways to control the proliferation problem.

The cat is out of the bag. We better start looking for a leash.

The idea was suggested to me by my friend Eric of Classical Values.

Other Instrumentation - Mass Spectrometer

It might be useful to have a Mass Spectrometer Optimized for Atomic masses in the range of 1 to 4 AMU, 1 to 12 AMU and 1 to 25 AMU, or other ranges as might seem handy.


Make your own Mass Spectrometer from off the shelf parts:

R. M. Jordan Co.

Holding Back Fusion

The Government Accountability Office (GAO) has just released a report on the state of nuclear fusion in America. It is not good. Here is an excerpt from the executive summary.
GAO has identified several challenges DOE faces in managing alternative fusion research activities. First, NNSA and the Office of Fusion Energy Sciences (OFES), which manage the inertial fusion program within DOE, have not effectively coordinated their research activities to develop inertial fusion as an energy source. For example, they do not have a coordinated research plan that identifies key scientific and technological issues that must be addressed to advance inertial fusion energy and how their research activities would meet those goals.

Second, DOE may find it difficult to manage competing funding priorities to advance both ITER-related research and alternative magnetic fusion approaches. DOE officials told GAO they are focusing limited resources on ITER-related research activities. As a result, as funding for ITER-related research has increased, the share of funding for the most innovative alternative magnetic fusion research activities decreased from 19 percent of the fusion research budget in fiscal year 2002 to 13 percent in fiscal year 2007. According to DOE officials, this level of funding is sufficient to meet research objectives. However, university scientists involved in fusion research told us that this decrease in funding has led to a decline in research opportunities for innovative concepts, which could lead to a simpler, less costly, or faster path to fusion energy, and reduced opportunities to attract students to the fusion sciences and train them to fulfill future workforce needs. Finally, while the demand for scientists and engineers to run experiments at ITER and inertial fusion facilities is growing, OFES does not have a human capital strategy to address expected future workforce shortages. These shortages are likely to grow as a large part of the fusion workforce retires over the next 10 years.
Inertial fusion is all about using laser pulses to create enough pressure to cause a pellet of fuel frozen to near absolute zero to implode with enough pressure to fuse the frozen elements. So far there is no plan to turn this into a power producer. Brilliant management. Just brilliant.

In addition they have no plan to meet their manpower requirements by training scientists and engineers. They should try reading The Mythical Man Monthby Brooks. They are setting themselves up for a regenerative failure.

Another inertial approach is the beam or IEC approach. Standing for Inertial Electrostatic Confinement. This uses electrostatic fields to focus and accelerate the beams with various methods used to reduce beam collisions with the accelerator electrodes. The Bussard Fusion Reactor is one example of such a device which uses magnetic fields to reduce losses. There are others.

Then we have the problem of ITER sucking up funds like a runaway Hoover. Choking off other promising approaches. Like alternative magnetic fusion approaches such as the Spheromak. Between all the magnetic approaches such as ITER, other tokamaks, other magnetic confinement approaches, and laser implosion, the budget for various IEC approaches is tiny indeed.

Here is an excerpt from the full report.
The ITER Organization faces several management challenges that may limit its ability to build ITER on time and on budget and may affect U.S. costs. Many of these challenges stem from the difficulty of coordinating the efforts of six countries and the European Union that are designing and building components for ITER and, as members of the ITER Organization, must reach consensus before making critical management decisions. The key management challenges include (1) developing quality assurance standards to test the reliability and integrity of the components made in different countries; (2) assembling, with a high level of precision, components and parts built in different countries; (3) finding a new vendor if a country fails to build a component on time or does not meet quality assurance standards; (4) developing a contingency fund that adequately addresses cost overruns and schedule delays; and (5) developing procedures that describe which countries will be responsible for paying for cost overruns.
I smell a boondoggle. The Euros had this problem with the Airbus A380 Fiasco. So you can't say they don't have enough experience to screw things up. They have had practice.

Here is more about the laser inertial confinement program.
DOE has three separately funded inertial fusion research programs: NNSA’s inertial fusion research activities related to the nuclear weapons program, a High Average Power Laser Program (HAPL) to develop technology needed for energy for which funding is directed by a congressional conference committee, and OFES’s inertial fusion research activities aimed at exploring the basic science for energy applications. Experiments in each of these programs help advance inertial fusion energy, but these experiments are not coordinated and each program has a separate mission and different scientific and technological objectives.
Evidently the European management model is popular in the USA too. Who knew?

I'm not sure exactly what program is being referred to here. It looks like IEC which is distributed among a number of labs and university locations.
As another alternative to both the laser systems and the Z-machine, OFES is funding experiments using heavy ion beams to produce fusion energy at the Lawrence Berkeley National Laboratory. Heavy ion beams are made by a particle accelerator—a device that uses electrical fields to propel electrically charged particles at high speeds. The heavy ions, which are heavier than carbon atoms, collide with the targets and cause the compression and heat needed to release fusion energy.

However, in fiscal year 2006, OFES spent about $21 million to fund 25 small-scale experiments at 11 universities, 4 national laboratories, and 2 private companies to test 7 types of magnetic fusion devices with different shapes and magnetic currents. This level of funding represents a decline over the past 6 fiscal years—from $26 million in fiscal year 2002 to $20 million in fiscal year 2007. University scientists involved in innovative fusion research told us that this decrease in funding was not consistent with a 1999 DOE fusion energy science advisory committee study that recommended OFES increase funding for innovative magnetic research activities. OFES relies on this advisory committee to establish priorities for the fusion program and to provide a basis for the allocation of funding.

However, since that report, the share of funding for innovative research activities has decreased even as funding for fusion research has increased. The share of funding has dropped from 19 percent of the fusion research budget in fiscal year 2002 to 13 percent in fiscal year 2007. In addition, while OFES’s 5-year budget plan shows an increase in funding for fusion research activities in fiscal years 2008 through 2011, most of this funding will be used for ITER- and tokamak-related research activities at the major facilities. DOE officials also told us there are planned increases in funding for innovative devices, but only to maintain the same level of research. According to university scientists, a number of innovative approaches are ready to advance to the next stage of development that would test the feasibility of producing fusion energy or conduct more sophisticated experiments, but DOE has no plans to advance any of these approaches because it may require an increase in funding to conduct more sophisticated experiments. DOE’s fusion energy advisory committee has not assessed the appropriate level of funding between ITER- and tokamak-related activities and innovative concepts since 1999, before the U.S. joined ITER and it became a priority.
So they are choking small money fusion research to pay for ITER. This is nuts when any one of the small approaches migh deliver a breakthrough that could reduce the time and money to develop actual fusion power.

So you get the idea. Typical big governmentitis. The ideas with the most political clout win. Ideas with small experiments, few researchers and low cost results get squeezed out because they lack a constituency.

Pretty much what Dr. Bussard said in the audio found here and the video found here.

If you think it is time for a change, contact your government.

House of Representatives
The Senate
The President

Give them an earful. The future will soon be upon us and we need to be ready.